CPC · California Plumbing Code

How do I size the water service, meter, and building supply piping?

Q: How do I decide between using Table 610.4 and Appendix A/M methods?

Use Table 610.4 when your installation falls within the Table’s stated conditions and you have the required inputs (minimum pressure, elevation difference, developed length, and total fixture units). If those inputs are unavailable or if you prefer hydraulic/chart methods, use Appendix A (recommended rules) or Appendix M for residential calculations. § 610.4 , § 610.7 , § 610.5 .

Q: What pressure should I use for sizing — average or minimum?

Design on the minimum daily service pressure available where pressure fluctuates. § 610.7(5) .

Q: What is the absolute minimum I can install for building supply and fixture branches?

The code sets 3/4 inch (20 mm) as the minimum building supply size (Table 610.4 method), and Appendix M states 1/2 inch (15 mm) as the minimum fixture branch in its residential sizing method. § 610.8 ; Appendix M M 102.7.1 .

The CPC requires sizing the water meter and building supply by total demand and pressure‑length conditions. Use the step sequence in § 610.8 with Table 610.4 (correct supply pressure for elevation at 1/2 psi per foot, pick the pressure range and length, then read the fixture‑unit capacity to find the meter and building‑supply sizes). Minimum building supply is 3/4". Appendix A or M methods are allowed alternatives and Appendix M includes a residential Water Demand Calculator and examples.

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Last reviewed: July 6, 2026

What the code requires — 2-4 sentences

The California Plumbing Code requires that the size of each water meter, water service (meter/street service) and building supply piping be based on the total demand (fixture units or design flow) and determined by the procedures in Chapter 6 (either by Table 610.4 or by the Appendix methods). Follow the step-by-step procedure in § 610.8 to use Table 610.4, and note that systems within the scope of Table 610.4 may be sized from that Table or by Appendix A/C/M methods per § 610.4 and § 610.5.

The simplest rule: determine available pressure (correct for elevation), pick the pressure group in Table 610.4, pick the length column ≥ your developed length, then read down to the fixture‑unit capacity and apply the meter and building‑supply sizes shown in the left columns.

Requirements in detail

Key defined terms (first appearance bolded)

Building supply pipe — the main pipe from the meter or other source into the building. No building supply pipe shall be less than 3/4 inch (20 mm) in diameter (minimum). § 610.8.
Fixture units — demand values for fixtures (use Table 610.3) used to total the building demand. § 610.3.
Developed length — the run length from the meter to the most remote outlet (use the developed length in Table 610.4 selection). § 610.7.

Procedure to size meter and building supply (step summary)

Follow these steps from § 610.8 (these are the required actions when using Table 610.4):

Determine the available pressure at the water meter or other source of supply. § 610.8(1).
Correct that pressure for elevation: add or subtract 1/2 psi (3.4 kPa) for each foot (305 mm) of elevation change between source and highest outlet. § 610.8(2).
Using the corrected pressure, pick the pressure‑range group in Table 610.4. § 610.8(3).
Select the length column in Table 610.4 equal to or longer than the developed length. § 610.8(4).
Move down that column to the fixture‑unit value ≥ total building fixture units (from Table 610.3). § 610.8(5).
Read the meter size and building supply size from the left columns associated with that fixture‑unit entry. § 610.8(6).

Notes and related sizing provisions:

When using Table 610.4, determine the items listed in § 610.7 (fixture units, developed length, elevation difference, supply/main pressure, and use minimum daily pressure if pressure fluctuates).
Devices that impose pressure loss (meters, backflow preventers, filters, tankless water heaters, etc.) must be included in the pressure‑loss calculation; do not size the meter/building supply without their pressure loss. § 610.2 and § 610.6.
The code allows alternative sizing by Appendix A (recommended rules) or Appendices C and M; Appendix M includes a Water Demand Calculator example and method for residential sizing. § 610.4, § 610.5, Appendix M.

Quick reference table (decision‑relevant values)

Decision item	Value / Action	Code Reference
Elevation correction	Add/subtract 1/2 psi per foot (3.4 kPa/305 mm) to the available pressure	§ 610.8(2)
Minimum building supply diameter	3/4 inch (20 mm) minimum	§ 610.8(6)
Minimum fixture branch size (residential / Appendix M)	1/2 inch (15 mm) (Appendix M.102.7.1 minimum)	Appendix M M 102.7.1
Must include device pressure losses (meter, backflow preventer, treatment devices)	Include in pressure‑loss calcs; inlet/outlet dia. of such devices not smaller than served piping when data absent	§ 610.2, § 610.6
Steps to use Table 610.4	Determine available pressure → elevation correction → pick pressure range → pick length column ≥ developed length → read fixture‑unit row → apply left‑column meter & building sizes	§ 610.7, § 610.8
Table location / scope	Table 610.4 lists fixture‑unit capacities by pressure ranges and length (use only when conditions in § 610.7 apply)	Table 610.4, § 610.4, § 610.7

Note: the full numeric entries in Table 610.4 (meter sizes vs fixture units for each pressure/length column) are used directly in the step sequence above; Table 610.4 is published in the code (see Table 610.4 header and pressure‑range headings). If you plan to use Table 610.4 directly, have the full Table available at plan check or site calculation.

Exceptions & special cases

Appendix methods allowed: Systems within Table 610.4 can be sized by that Table OR sized per Appendix A methods or alternative Appendix C / Appendix M methods where adopted; Appendix M provides a Water Demand Calculator for residential sizing. § 610.4, § 610.5, Appendix M.
Where pressure fluctuates in the main, design on the minimum pressure available per § 610.7(5).
Where installed devices (filter, backflow preventer, softener, tankless heater) do not have published pressure‑loss data, the code requires their inlet/outlet diameter be not less than the pipe they serve (cannot create an undocumented bottleneck). § 610.2.
Flushometer valves: when sizing systems serving flushometer valves, assign fixture units per Table 610.10 and ensure piping to the flushometer is not less than the valve inlet. § 610.10 and Table 610.10.

Common mistakes

Ignoring elevation correction: failing to add/subtract 1/2 psi per foot can cause undersizing. § 610.8(2).
Forgetting device pressure loss: leaving off meter, backflow device, or treatment device head loss when selecting sizes. § 610.2, § 610.6.
Picking a length column shorter than the developed length or using average pressure instead of the minimum available when pressure fluctuates. § 610.7, § 610.8(4).
Using Table 610.4 where conditions in § 610.7 aren’t met (e.g., unknown supply pressure, or fixtures outside the Table’s scope) instead of sizing per Appendix A/C/M. § 610.4, § 610.7.
Installing a building supply less than the code minimum 3/4 inch. § 610.8.

Worked example — residential sizing (practical, uses Appendix M example in the code)

This example shows the Appendix M method (permitted alternative to Table 610.4 in § 610.4/§ 610.5) because the code provides a clear worked example for residential demand and resulting building supply size.

Scenario: a small house with the six efficient fixtures used in Appendix M Example 1 (the code example):

The Water Demand Calculator example for six efficient fixtures produces a 99th‑percentile design flow of 8.5 gpm (0.54 L/s). Appendix M example (Water Demand Calculator) shows this.
Appendix M Example 1 then uses Chart A 105.1(1) (Appendix A) and concludes a 3/4 inch (20 mm) building supply can convey the peak demand in that example (the code example’s conclusion is a 3/4‑inch minimum). See Appendix M example and Chart A discussion. M 102 and Appendix A examples.

Step‑by‑step (how you would do it in practice):

Add fixture counts into the Water Demand Calculator (Appendix M) and run to get design flow (gpm). Appendix M. M 102.3–M 102.5.
Add any continuous outdoor loads (hose bibbs, irrigation) per M 102.5.
With the design gpm, consult Appendix A Chart A 105.1 (or the Water Demand Calculator outputs/table) to find the pipe diameter that will carry that gpm at allowable friction. Appendix M Example shows 8.5 gpm → 3/4 in in the code example. M 102 and Appendix A.

If you prefer to use Table 610.4 instead of Appendix M/A, follow the steps in § 610.8 (pressure → elevation correction → pressure range → length column → fixture‑unit lookup → read meter & building sizes). You will need the full numeric Table 610.4 at hand to read the meter and pipe diameters for your specific pressure/length/fixture‑unit combination. § 610.8 and Table 610.4.

Related provisions (quick links to the CPC text you will use)

§ 610.0 — Size of potable water piping (scope).
§ 610.1 — Size (general rule: base on total demand).
§ 610.4 — Sizing water supply and distribution systems; use Table 610.4 or Appendix methods.
§ 610.7 — Conditions required to use Table 610.4 (what you must know before using it).
§ 610.8 — Step‑by‑step procedure to size meter and building supply using Table 610.4.
§ 610.9 — Size of branches when Table 610.4 is used.
§ 610.10 and Table 610.10 — Flushometer valve fixture‑unit assignments when using Table 610.4.
Appendix A — detailed friction/length charts and sizing charts (Chart A 105.1 series).
Appendix M — Water Demand Calculator and residential examples (alternative sizing method).

Code references

Grounded in the retrieved California Plumbing Code — click a citation to read the verbatim passage:

CPC § 610.6 High relevance — show source text
610.6 Friction and Pressure Loss. Except where the type of pipe used and the water characteristics are such that no decrease in capacity due to the length of service (age of system) is expected, friction-loss data shall be obtained from the “Fairly Rough” or “Rough” charts in Appendix A of this code. Friction or pressure losses in a water meter, valve, and fittings shall be obtained from the same sources. Pressure losses through water-treating equipment, backflow prevention devices, or other flow-restricting devices shall be computed in accordance with Section 610.2. 610.7 Conditions for Using Table 610.4. On a proposed water piping installation sized using Table 610.4, the following conditions shall be determined:

(1) Total number of fixture units as determined from Table 610.3, Equivalent Fixture Units, for the fixtures to be installed.

(2) Developed length of supply pipe from meter to the most remote outlet.

(3) Difference in elevation between the meter or other source of supply and the highest fixture or outlet.

(4) Pressure in the street main or another source of supply at the locality where the installation is to be made.

(5) In localities where there is a fluctuation of pressure in the main throughout the day, the water piping system shall be designed on the basis of the minimum pressure available. 610.8 Size of Meter and Building Supply Pipe Using Table 610.4. The size of the meter and the building supply pipe shall be determined as follows:

(1) Determine the available pressure at the water meter or other source of supply.

(2) Add or subtract depending on positive or negative elevation change, [1] ⁄ 2 psi (3.4 kPa) for each foot (305 mm) of difference in elevation between such source of supply and the highest water supply outlet in the building or on the premises.

(3) Use the “pressure range” group within which this pressure will fall using Table 610.4.

(4) Select the “length” column that is equal to or longer than the required length.

(5) Follow down the column to a fixture unit value equal to or exceeding the total number of fixture units required by the installation.

(6) Having located the proper fixture unit value for the required length, sizes of meter and building supply pipe as found in the two left-hand columns shall be applied.

No building supply pipe shall be less than [3] ⁄ 4 of an inch (20 mm) in diameter.

610.9 Size of Branches. Where Table 610.4 is used, the minimum size of each branch shall be determined by the total fixture units served by that branch and then following the steps in Section 610.8. No branch piping shall exceed the total demand in fixture units for the system computed from Table 610.3.

610.10 Sizing for Flushometer Valves. Where using Table 610.4 to size water supply systems serving flushometer valves, the number of flushometer fixture units assigned to every section of pipe, whether branch or main, shall be determined by the number and category of flushometer valves served by that section of pipe, in accordance with Table 610.10. Piping supplying a flushometer valve shall be not less in size than the valve inlet.

Where using Table 610.10 to size water piping, care shall be exercised to assign flushometer fixture units based on the number and category of fixtures served.

|TABLE 610.
CPC § 609.4 High relevance — show source text
609.4 Testing . . . . . . . . . . . . . . . . . . . . .155

609.5 Unions . . . . . . . . . . . . . . . . . . . . .155

609.6 Location . . . . . . . . . . . . . . . . . . . .155

609.7 Abutting Lot . . . . . . . . . . . . . . . . .155

609.8 Pumps . . . . . . . . . . . . . . . . . . . . .155

609.9 Low-Pressure Cutoff Required on Booster Pumps for Water Distribution Systems . . . . . . . . . . .156

2025 CALIFORNIA PLUMBING CODE xxxiii

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TABLE OF CONTENTS

609.10 Disinfection of Potable Water System . . . . . . . . . . . . . . . . . . . . .156

609.11 Water Hammer . . . . . . . . . . . . . . .156

609.12 Pipe Insulation . . . . . . . . . . . . . . .156

610.0 Size of Potable Water Piping . . . .156

610.1 Size . . . . . . . . . . . . . . . . . . . . . . . .156

610.2 Pressure Loss . . . . . . . . . . . . . . . .156

610.3 Quantity of Water . . . . . . . . . . . . .157

610.4 Sizing Water Supply and Distribution Systems . . . . . . . . . . .157

610.5 Sizing per Appendices A, C, and M . . . . . . . . . . . . . . . . .157

610.6 Friction and Pressure Loss . . . . . .157

610.7 Conditions for Using Table 610.4 . . . . . . . . . . . . . . . . . .157

610.8 Size of Meter and Building Supply Pipe Using Table 610.4 . .157

610.9 Size of Branches . . . . . . . . . . . . .157

610.10 Sizing for Flushometer Valves . . .157

Table 610.10 Flushometer Fixture Units for Water Sizing Using Table 610.3 . . . . . . . . . . . . . . . . . .157

Table 610.3 Water Supply Fixture Units (WSFU) and Minimum Fixture Branch Pipe Sizes . . . . . . . . . . . .158

Table 610.4 Fixture Unit Table for

Determining Water Pipe and Meter Sizes . . . . . . . . . . . . . .159

610.11 Sizing Systems for Flushometer Tanks . . . . . . . . . . . .160

610.12 Sizing for Velocity . . . . . . . . . . . . .160

610.13 Exceptions . . . . . . . . . . . . . . . . . .160

611.0 Drinking Water Treatment Units . . . . . . . . . . . . . . . . . . . . . . .160

611.1 Application . . . . . . . . . . . . . . . . . .160
CPC § 609.12.3 High relevance — show source text
(2) Hot water piping between the fixture control valve or supply stop and the fixture or appliance shall not be required to be insulated. 609.12.3 California Energy Code Pipe Insulation Requirements. [CEC] See California Energy Code Sec- tions 150.0(j)2 and 120.3(c) for pipe insulation require- ments based on fluid temperature and pipe diameter – for domestic hot water piping. The California Energy Code requires that piping that penetrates metal framing shall use grommets, plugs, wrapping or other insulating mate- rial to assure that no contact is made with the metal fram- ing. The California Energy Code also requires that insulation shall abut securely against all framing mem- bers, and places conditions on when installed wall or attic insulation that surrounds installed piping can be consid- ered to provide pipe insulation meeting requirements.

610.0 Size of Potable Water Piping. 610.1 Size. The size of each water meter and each potable water supply pipe from the meter or other source of supply to the fixture supply branches, risers, fixtures, connections, outlets, or other uses shall be based on the total demand and shall be determined according to the methods and procedures outlined in this section. Water piping systems shall be designed to ensure that the maximum velocities allowed by the code and the applicable standard are not exceeded.

610.2 Pressure Loss. Where a water filter, water softener, backflow prevention device, tankless water heater, or similar device is installed in a water supply line, the pressure loss through such devices shall be included in the pressure loss calculations of the system, and the water supply pipe and meter shall be adequately sized to provide for such a pressure loss.

No water filter, water softener, backflow prevention device, or similar device regulated by this code shall be installed in a potable water supply piping where the installation of such device produces an excessive pressure drop in such water supply piping. In the absence of specific pressure drop information, the diameter of the inlet or outlet of such device or its connecting piping shall be not less than the diameter of such water distribution piping to the fixtures served by the device.

156 2025 CALIFORNIA PLUMBING CODE

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WATER SUPPLY AND DISTRIBUTION

Such devices shall be of a type approved by the Authority Having Jurisdiction and shall be tested for flow rating and pressure loss by an approved laboratory or recognized testing agency to standards consistent with the intent of this chapter. 610.3 Quantity of Water. The quantity of water required to be supplied to every plumbing fixture shall be represented by fixture units, as shown in Table 610.3. Equivalent fixture values shown in Table 610.3 include both hot and cold water demand.

610.4 Sizing Water Supply and Distribution Systems. Systems within the range of Table 610.4 shall be permitted to be sized from that table or by the method in accordance with Section 610.5.

Listed parallel water distribution systems shall be installed in accordance with their listing, but at no time shall a portion of the system exceed the maximum velocities allowed by the code. 610.5 Sizing per Appendices A, C, and M **.
CPC § 610.3 High relevance — show source text
No water filter, water softener, backflow prevention device, or similar device regulated by this code shall be installed in a potable water supply piping where the installation of such device produces an excessive pressure drop in such water supply piping. In the absence of specific pressure drop information, the diameter of the inlet or outlet of such device or its connecting piping shall be not less than the diameter of such water distribution piping to the fixtures served by the device.

156 2025 CALIFORNIA PLUMBING CODE

), Copyright © 2025 IAPMO, and may not be used for any other purpose or distributed to any other persons or parties.

WATER SUPPLY AND DISTRIBUTION

Such devices shall be of a type approved by the Authority Having Jurisdiction and shall be tested for flow rating and pressure loss by an approved laboratory or recognized testing agency to standards consistent with the intent of this chapter. 610.3 Quantity of Water. The quantity of water required to be supplied to every plumbing fixture shall be represented by fixture units, as shown in Table 610.3. Equivalent fixture values shown in Table 610.3 include both hot and cold water demand.

610.4 Sizing Water Supply and Distribution Systems. Systems within the range of Table 610.4 shall be permitted to be sized from that table or by the method in accordance with Section 610.5.

Listed parallel water distribution systems shall be installed in accordance with their listing, but at no time shall a portion of the system exceed the maximum velocities allowed by the code. 610.5 Sizing per Appendices A, C, and M . Except as provided in Section 610.4, the size of each water piping system shall be determined in accordance with the procedure set forth in Appendix A. For alternative methods of sizing water supply systems, see Appendix C or Appendix M . 610.6 Friction and Pressure Loss. Except where the type of pipe used and the water characteristics are such that no decrease in capacity due to the length of service (age of system) is expected, friction-loss data shall be obtained from the “Fairly Rough” or “Rough” charts in Appendix A of this code. Friction or pressure losses in a water meter, valve, and fittings shall be obtained from the same sources. Pressure losses through water-treating equipment, backflow prevention devices, or other flow-restricting devices shall be computed in accordance with Section 610.2. 610.7 Conditions for Using Table 610.4. On a proposed water piping installation sized using Table 610.4, the following conditions shall be determined:

(1) Total number of fixture units as determined from Table 610.3, Equivalent Fixture Units, for the fixtures to be installed.

(2) Developed length of supply pipe from meter to the most remote outlet.

(3) Difference in elevation between the meter or other source of supply and the highest fixture or outlet.

(4) Pressure in the street main or another source of supply at the locality where the installation is to be made.

(5) In localities where there is a fluctuation of pressure in the main throughout the day, the water piping system shall be designed on the basis of the minimum pressure available. 610.8 Size of Meter and Building Supply Pipe Using Table 610.4. The size of the meter and the building supply pipe shall be determined as follows:

(1) Determine the available pressure at the water meter or other source of supply.
CPC § 610.5 High relevance — show source text
610.5 Sizing per Appendices A, C, and M . . . . . . . . . . . . . . . . .157

610.6 Friction and Pressure Loss . . . . . .157

610.7 Conditions for Using Table 610.4 . . . . . . . . . . . . . . . . . .157

610.8 Size of Meter and Building Supply Pipe Using Table 610.4 . .157

610.9 Size of Branches . . . . . . . . . . . . .157

610.10 Sizing for Flushometer Valves . . .157

Table 610.10 Flushometer Fixture Units for Water Sizing Using Table 610.3 . . . . . . . . . . . . . . . . . .157

Table 610.3 Water Supply Fixture Units (WSFU) and Minimum Fixture Branch Pipe Sizes . . . . . . . . . . . .158

Table 610.4 Fixture Unit Table for

Determining Water Pipe and Meter Sizes . . . . . . . . . . . . . .159

610.11 Sizing Systems for Flushometer Tanks . . . . . . . . . . . .160

610.12 Sizing for Velocity . . . . . . . . . . . . .160

610.13 Exceptions . . . . . . . . . . . . . . . . . .160

611.0 Drinking Water Treatment Units . . . . . . . . . . . . . . . . . . . . . . .160

611.1 Application . . . . . . . . . . . . . . . . . .160

611.2 Air Gap Discharge . . . . . . . . . . . .160

611.3 Connection Tubing . . . . . . . . . . . .160

611.4 Sizing of Residential Softeners . . .160

612.0 Residential Fire Sprinkler Systems . . . . . . . . . . . . . . . . . . . .160

612.1 Installation . . . . . . . . . . . . . . . . . .160

Table 611.1 Drinking Water Treatment Units . . . . . . . . . . . . . . . . . . . . . . .161

Table 611.4 Sizing of Residential Water Softeners . . . . . . . . . . . . . . . . . . .161

613.0 Domestic Hot-Water Distribution Systems for Health Facilities and Clinics . . . . . . . . . . . . . . . . . .161

Table 613.1 Hot Water Use . . . . . . . . . . . . . . . . .161

614.0 Dialysis Water-Distribution Systems . . . . . . . . . . . . . . . . . . . . . .162

615.0 Identification of Potable and

Nonpotable Water Lines . . . . . . . . .162

615.1 Uses Not Permitted . . . . . . . . . . . . .162

616.0 Emergency Water Supply . . . . . . . .162

CHAPTER 7 SANITARY DRAINAGE . . . . . . . .163

PART I Drainage Systems . . . . . . . . . . .165
CPC § 0.06 High relevance — show source text
For SI units: 1 gallon per minute = 0.06 L/s

M 102.2 Water Demand Calculator. The estimated design flow rate for the building supply and principal branches and risers shall be determined by the IAPMO Water Demand Calculator available for download at http://www.iapmo.org/ WEStand/Pages/WaterDemandCalculator.aspx

M 102.3 Meter and Building Supply. To determine the design flow rate for the water meter and building supply, enter the total number of indoor plumbing fixtures and appliances for the building in Column [B] of the Water Demand Calculator and run Calculator. See Table M 102.3 for an example.

M 102.4 Fixture Branches and Fixture Supplies. To determine the design flow rate for fixture branches and risers, enter the total number of plumbing fixtures and appliances

TABLE M 102.1

DESIGN FLOW RATE FOR WATER-CONSERVING PLUMBING

FIXTURES AND APPLIANCES IN RESIDENTIAL OCCUPANCIES

for the fixture branch or riser in Column [B] of the Water Demand Calculator and run Calculator. The flow rate for one fixture branch and one fixture supply shall be the design flow rate of the fixture according to Table M 102.1.

M 102.5 Continuous Supply Demand. Continuous supply demands in gallons per minute (gpm) for lawn sprinklers, air conditioners, hose bibbs, etc., shall be added to the total estimated demand for the building supply as determined by Section M 102.3. Where there is more than one hose bibb installed

on the plumbing system, the demand for only one hose bibb shall be added to the total estimated demand for the building supply. Where a hose bibb is installed on a fixture branch, the demand of the hose bibb shall be added to the design flow rate for the fixture branch as determined by Section M 102.4.

M 102.6 Other Fixtures. Fixtures not included in Table M

102.1 shall be added in Rows 12 through 14 in the Water Demand Calculator as Other Fixture. The probability of use and flow rate for Other Fixtures shall be added by selecting the comparable probability of use and flow rate from Columns

[C] and [E].

M 102.7 Size of Water Piping per Appendix A. Except as provided in Section M 102.0 for estimating the demand load for single- and multi-family dwellings, the size of each water piping system shall be determined in accordance with the procedure set forth in Appendix A. After determining the permissible friction loss per 100 feet (30 480 mm) of pipe in accordance with Section A 104.0 and the demand flow in

accordance with the Water Demand Calculator, the diameter of the building supply pipe, branches and risers shall be obtained from Chart A 105.1(1) through Chart A 105.1(7), whichever is applicable, in accordance with Section A 105.0 and Section A 106.0. Velocities shall be in accordance with

Section A 107.0. Appendix I (IS 31), Figure 3 and Figure 4 shall be permitted when sizing PEX systems.

M 102.7.1 Minimum Fixture Branch Size. The minimum fixture branch size shall be [1] / 2 inch (15 mm) in diameter.

For SI units: 1 gallon per minute = 0.06 L/s

2025 CALIFORNIA PLUMBING CODE 519

CPC § 610.4. High relevance — show source text

(3) Use the “pressure range” group within which this pressure will fall using Table 610.4.

(4) Select the “length” column that is equal to or longer than the required length.

(5) Follow down the column to a fixture unit value equal to or exceeding the total number of fixture units required by the installation.

(6) Having located the proper fixture unit value for the required length, sizes of meter and building supply pipe as found in the two left-hand columns shall be applied.

No building supply pipe shall be less than [3] ⁄ 4 of an inch (20 mm) in diameter.

610.9 Size of Branches. Where Table 610.4 is used, the minimum size of each branch shall be determined by the total fixture units served by that branch and then following the steps in Section 610.8. No branch piping shall exceed the total demand in fixture units for the system computed from Table 610.3.

610.10 Sizing for Flushometer Valves. Where using Table 610.4 to size water supply systems serving flushometer valves, the number of flushometer fixture units assigned to every section of pipe, whether branch or main, shall be determined by the number and category of flushometer valves served by that section of pipe, in accordance with Table 610.10. Piping supplying a flushometer valve shall be not less in size than the valve inlet.

Where using Table 610.10 to size water piping, care shall be exercised to assign flushometer fixture units based on the number and category of fixtures served.

TABLE 610.10 FLUSHOMETER FIXTURE UNITS FOR WATER SIZING USING TABLE 610.3	Col2	Col3
FIXTURE CATEGORY: WATER CLOSET WITH FLUSHOMETER VALVES	FIXTURE CATEGORY: WATER CLOSET WITH FLUSHOMETER VALVES	FIXTURE CATEGORY: WATER CLOSET WITH FLUSHOMETER VALVES
NUMBER OF FLUSHOMETER VALVES	INDIVIDUAL FIXTURE UNITS ASSIGNED IN DECREASING VALUE	FIXTURE UNITS ASSIGNED FOR WATER CLOSETS AND SIMILAR 10-UNIT FIXTURES IN ACCUMULATIVE VALUES
1	40	40
2	30	70
3	20	90
4	15	105
5 or more	10 each	115 plus 10 for each additional fixture in excess of 5
FIXTURE CATEGORY: URINALS WITH FLUSHOMETER VALVES	FIXTURE CATEGORY: URINALS WITH FLUSHOMETER VALVES	FIXTURE CATEGORY: URINALS WITH FLUSHOMETER VALVES
NUMBER OF FLUSHOMETER VALVES	INDIVIDUAL FIXTURE UNITS ASSIGNED IN DECREASING VALUE	FIXTURE UNITS ASSIGNED FOR URINALS AND SIMILAR **5-UNIT FIXTURES

CPC § 1.75 High relevance — show source text

250|1.75|0.65|3.25|9.25|6.00|303844|303844| |1/0|2|SAPT-1/0-26|YE25R-60|0.250|1.75|0.65|3.25|9.25|6.00|303845|303845| |4/0|2/0|SAPT-4/0-206|YE28R-60|0.375|1.54|0.91|3.50|10.9|6.00|303846|W249
U249
U2492| |350|4/0|PTB-350-6|YE31AG3|0.460|2.25|1.12|4.70|10.7|6.00|303554|−
U31ART
U31ART2| |500/60
0|500|PTM-500-346|YE34AP-
GE|0.750|2.56|1.57|6.30|12.3|6.00|300013|−
U34ART3
U34ART2,3| |700|500|PTL-750|YE39AGB|0.750|2.56|1.60|6.30|12.3|6.00|303555|−
−
P39ART| |1,000|700|PTF-1000-34
6|YE44AG7|0.750|2.56|1.60|6.30|12.3|6.00|033757|−
−
P44ART|

1 Within this column, the first entry corresponds to a 6-ton press tool, the second entry corresponds to a 12-ton press tool, and the third entry corresponds to a 15-ton press tool. 2 A U-die adapter must be used when utilizing U-dies in 15-ton press tool. 3 Homac equivalent of this die is 106A.

Notes

The material for the pin terminals is on Table 41. Copper Rod-Soft Drawn, Tinned, Aluminum Connector EC Grade, Untinned
Connector is supplied pre-filled with inhibitor and sealed.
Connector is supplied pre-filled with inhibitor and sealed.
Pin terminals connected to copper secondary conductors use a copper connector. Pin terminals connected to aluminum secondary conductors use a fired wedge or h-tap.

Application

To make straight connections of insulated aluminum secondary neutral to bare copper neutral, see Note 10 Page 7.
To connect aluminum primary stress cone termination to terminal tap connector or cutout.
To make watertight termination for secondary risers.

015251 Page 38 of 39 Rev. #07: 03-25-22

UG-1: Connectors Greenbook Connectors for Insulated Cables Underground Distribution Systems

Pin Terminals (continued)

Table 42 Color Coding	Col2
Color Coding Requirements for Plastic End Plugs in Pin Terminals	Color Coding Requirements for Plastic End Plugs in Pin Terminals
Conductor Size	Plug Color
#6	Blue
#2	Red
1/0	Yellow
4/0	Pink
350	Brown
700	Purple

Table 43 Specifications and Ordering Information for Copper Pin Terminal

CPC § 201.1 High relevance — show source text

TABLE H 201.1(1) CAPACITY OF SEPTIC TANKS [1, 2, 3, 4]

MINIMUM HORIZONTAL DISTANCE	BUILDING SEWER	SEPTIC TANK	DISPOSAL FIELD	SEEPAGE PIT OR CESSPOOL
Building or structures1	2 feet	5 feet	8 feet	8 feet
Property line adjoining pri- vate property	Clear2	5 feet	5 feet	8 feet
Water supply wells	50 feet3	50 feet	100 feet	150 feet
Streams and other bodies of water	50 feet	50 feet	100 feet7	150 feet7
Trees	–	10 feet	–	10 feet
Seepage pits or cesspools8	–	5 feet	5 feet	12 feet
Disposal field8	–	5 feet	4 feet4	5 feet
On-site domestic water service line	1 foot5	5 feet	5 feet	5 feet
Distribution box	–	–	5 feet	5 feet
Pressure public water main	10 feet6	10 feet	10 feet	10 feet

For SI units: 1 foot = 304.8 mm

Notes: 1 Including porches and steps, whether covered or uncovered, breezeways, roofed porte cocheres, roofed patios, carports, covered walks, covered driveways, and similar structures or appurtenances. 2 See Section 312.3. 3 Drainage piping shall clear domestic water supply wells by not less than 50 feet (15 240 mm). This distance shall be permitted to be reduced to not less than 25 feet (7620 mm) where the drainage piping is constructed of materials approved for use within a building. 4 Plus 2 feet (610 mm) for each additional 1 foot (305 mm) of depth more than 1 foot (305 mm) below the bottom of the drain line. (See Section H 601.0) 5 See Section 720.0. 6 For parallel construction – For crossings, approval by the Health Department shall be required. 7 These minimum clear horizontal distances shall also apply to disposal fields, seepage pits, and the mean high-tide line. 8 Where disposal fields, seepage pits, or both are installed in sloping ground, the minimum horizontal distance between any part of the leaching system and ground surface shall be 15 feet (4572 mm).

CPC § 102.2 High relevance — show source text
CHART A 102.2

FRICTION LOSSES FOR DISK-TYPE WATER METERS

FLOW (gallons per minute)

For SI units: 1 inch = 25 mm, 1 pound-force per square inch = 6.8947 kPa, 1 gallon per minute = 0.06 L/s

2025 CALIFORNIA PLUMBING CODE 367

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APPENDIX A

A 104.2 Elevation. Determine the elevation of the highest fixture or group of fixtures above the water (street) main. Multiply this difference in elevation by 0.43. The result is the loss of static pressure in psi (kPa). A 104.3 Available Pressure. Subtract the sum of loss in static pressure and the residual pressure to be maintained at the highest fixture from the average minimum daily service pressure. The result will be the pressure available for friction loss in the supply pipes, where no water meter is used. Where a meter is to be installed, the friction loss in the meter for the estimated maximum demand should also be subtracted from the service pressure to determine the pressure loss available for friction loss in the supply pipes. A 104.4 Developed Length. Determine the developed length of pipe from the water (street) main to the highest fixture. Where close estimates are desired, compute with the aid of Table A 104.4(1), Table A 104.4(2), or Table A 104.4(3), whichever is applicable, the equivalent length of pipe for fittings in the line from the water (street) main to the highest fixture and add the sum to the developed length. The pressure available for friction loss in psi (kPa), divided by the developed lengths of pipe from the water (street) main to the highest fixture, times 100, will be the average permissible friction loss per 100 feet (30 480 mm) length of pipe.

A 105.0 Size of Building Supply. A 105.1 Diameter. Knowing the permissible friction loss per 100 feet (30 480 mm) of pipe and the total demand, the diameter of the building supply pipe shall be permitted to be obtained from Chart A 105.1(1), Chart A 105.1(2), Chart A 105.1(3), Chart A 105.1(4), Chart A 105.1(5), Chart A 105.1(6), or Chart A 105.1(7), whichever is applicable. The diameter of pipe on or next above the coordinate point corresponding to the estimated total demand and the permissible friction loss will be the size needed up to the first branch from the building supply pipe. A 105.2 Copper and Copper Alloy Piping. Where copper tubing or copper alloy pipe is to be used for the supply piping and where the character of the water is such that slight changes in the hydraulic characteristics are expected, Chart A 105.1(1) shall be permitted to be used. A 105.3 Hard Water. Chart A 105.1(2) shall be used for ferrous pipe with the most favorable water supply in regards to corrosion and caking. Where the water is hard or corrosive, Chart A 105.1(3) or Chart A 105.1(4) will be applicable.
CPC § 502.7 High relevance — show source text
L 502.7 Maximum Volume and Length of Hot Water. The maximum volume of water contained in a hot water

branch shall be in accordance with Section L 502.7.1. The maximum length per volume of piping shall comply with Section L 502.7.2.

L 502.7.1 Maximum Volume of Hot Water in a Branch. The water volume per foot of piping shall be calculated using Table L 502.7.1. The maximum volume of water in a fixture branch between any source of hot water (water heaters, recirculation loops and electrically heat traced pipe shall be considered sources of hot water) and the fixture fitting shall be:

(1) 24 oz (710 mL) where a single branch serves a single fixture.

(2) 40 oz (1183 mL) where a series branch incorporating one or more flow-through design configurations that serves two or more fixtures.

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APPENDIX L

«

«

(3) 60 oz (1774 mL) where a ring branch incorporating two or more flow-through design configurations that serves two or more fixtures.

Exceptions:

(1) The maximum volume of a single branch or series branch between any source of hot water and a kitchen sink and dishwasher located on an island or a peninsula where the floor is a concrete slab shall not contain more than 40 oz (1183 mL).

(2) The maximum volume of a single branch to a standalone tub shall not contain more than 80 oz (2366 mL).

L 502.7.2 Maximum Length Per Volume of Water in a Branch. For fixture branches in accordance with Section L 502.7.1, the maximum length of piping shall be calculated using Table L 502.7.2(1) through Table 502.7.2(4). Where a fixture fitting shut off valve (supply stop) is installed ahead of the fixture fitting, the maximum length is measured between the source of hot water and the fixture fitting shut off valve (supply stop).

L 502.7.3 Hot Water System Submeters. Where a hot water pipe from a circulation loop or electric heat trace line is equipped with a submeter, the hot water distribution system downstream of the submeter shall have either an end-of-line hot water circulation pump or shall be electrically heat traced. The maximum volume of water in a branch from the circulation loop or electric heat trace line downstream of the submeter shall not exceed 16 oz (473 mL).

Where there is no circulation loop or electric heat traced line downstream of the submeter, the submeter shall be located within 2 feet (610 mm) of the central hot water system; or the branch line to the submeter shall be circulated or heat traced to within 2 feet (610 mm) of the submeter. The maximum volume from the submeter to each fixture shall not exceed 32 oz (946 mL).

The circulation pump controls shall comply with the provisions of Section L 501.4.

L 503.0 Service Hot Water – Other Than Low-Rise Residential Buildings.

L 503.1 General. The service hot water, other than singlefamily houses, multifamily structures of three stories or fewer above grade, and modular houses shall comply with this section.
CPC § 1.11.0. High relevance — show source text
This state agency does not adopt sections identified with the following symbol: The Office of the State Fire Marshal’s adoption of this chapter or individual sections is applicable to structures regulated by other state agencies pursuant to Section 1.11.0.

2025 CALIFORNIA PLUMBING CODE 365

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366 2025 CALIFORNIA PLUMBING CODE

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APPENDIX A

RECOMMENDED RULES FOR SIZING THE WATER SUPPLY SYSTEM

The provisions contained in this appendix are not mandatory unless specifically adopted by a state agency, or referenced in the adopting ordinance.

A 101.0 General.

A 101.1 Applicability. This appendix provides a general procedure for sizing a water supply system. Because of the variable conditions encountered, it is impractical to lay down definite detailed rules of procedure for determining the sizes of water supply pipes in an appendix, which shall necessarily be limited in length. For an adequate understanding of the problems involved, refer to Water-Distributing Systems for Buildings, Report BMS 79 of the National Bureau of Standards; and Plumbing Manual, Report BMS 66, also published by the National Bureau of Standards.

A 102.0 Preliminary Information. A 102.1 Daily Service Pressure. Obtain the necessary information regarding the minimum daily service pressure in the area where the building is to be located. A 102.2 Water Meter. Where the building supply is to be metered, obtain information regarding friction loss relative to the rate of flow of meters in the range of sizes likely to be used. Friction-loss data is capable of being obtained from most manufacturers of water meters. Friction losses for disktype meters shall be permitted to be obtained from Chart A 102.2.

A 102.3 Local Information. Obtain available local information regarding the use of different kinds of pipe with respect both to durability and to decrease in capacity with the length of service in the particular water supply.

A 103.0 Demand Load.

A 103.1 Supply Demand. Estimate the supply demand for the building main, the principal branches and risers of the system by totaling the fixture units on each, Table A 103.1, and then by reading the corresponding ordinate from Chart A 103.1(1) or Chart A 103.1(2), whichever is applicable.

Exception: [HCD 1 & HCD 2] For the applicable fixtures, the supply demand flow rate values calculated using Appen- dix M may be substituted for the flow rates calculated using the fixture units in Table A 103.1 and Chart A 103.1(1) or Chart A 103.1(2), whichever is applicable.

A 103.2 Continuous Supply Demand. Estimate continuous supply demands in gallons per minute (gpm) (L/s) for lawn sprinklers, air conditioners, etc., and add the sum to the total demand for fixtures. The result is the estimated supply demand of the building supply.

A 104.0 Permissible Friction Loss.

A 104.1 Residual Pressure. Decide what is the desirable
CPC § 8.5 High relevance — show source text
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APPENDIX M

tion process. Because fixtures for outdoor water use may operate continuously for very long periods, they are not included in the WDC. To account for water use from one or more outdoor fixtures, add the demand of the single outdoor fixture with the highest flowrate to the calculated demand for indoor water use. With two hose bibbs, the demand of only one hose bibb is included. Hence, in this example, the total demand for the whole house is 8.5 gpm (0.54 L/s) + 2.0 gpm (0.13 L/s) = 10.5 gpm (0.662 L/s).

Solution: Step 2 of 2 – Determine the Pipe Size of the Building Supply.

Table 1 shows that at 10.5 gpm (0.662 L/s) the building supply shall be [3] / 4 inch (20 mm) in diameter.

Example 3: Indoor, Outdoor and Other Fixture Water Use – Find the pipe size for the water supply [Figure 1, Pipe Section 4] if the building in Example 2 adds a kitchen pot filler and a dog bath each with a faucet flow rate of 5.5 gpm (0.35 L/s).

Solution: Step 1 of 2 – Find Demand Load for the Build- ing Supply.

The kitchen pot filler and dog bath are not listed in Column

[A] of the WDC. To accommodate cases such as this, the WDC provides up to three additional rows for “Other Fixtures”. Enter the kitchen pot filler and dog bath in Column

[A] of the WDC and enter the fixture count for each in Column [B]. Find an indoor fixture that has a similar probability of use in Column [C] and add that to the column. Finally, enter the flow rate of the kitchen pot filler and dog bath in Column [D]. The estimated indoor water demand for the whole building is 11 gpm, as shown in the WDC in Figure 4.

As illustrated in Example 2, the hose bibb will increase the total demand for the whole house to 13 gpm (0.820 L/s).

Note that a reset button is provided to clear any numbers in Column [B] from a previous calculation.

Solution: Step 2 of 2 – Determine the Pipe Size of the Building Supply.

Table 1 shows that at 13 gpm (0.820 L/s) the building supply shall be 1inch (25 mm) in diameter.

Example 4: Sizing Branches and Risers – For individual hot and cold branches, repeat Steps 1 and 2. For example, for the hot water branch at the water heater [Figure 1, Pipe Section 3], enter all the fixtures and appliances that use hot water into the Water Demand Calculator (toilets will be excluded) as seen in Figure 5. Use the calculated demand load to find the pipe size in Step 2. Table 1 shows that at 7.7 (0.49 L/s) gpm, the hot water branch shall be [3] / 4 inch (20 mm) in diameter.

CPC § 422.1 Medium relevance — show source text

6 Assembly [Public Use (See Table 422.1)]. 7 Where sizing flushometer systems, see Section 610.10. 8 Reduced fixture unit loading for additional hose bibbs is to be used where sizing total building demand and for pipe sizing where more than one hose bibb is supplied by a segment of water distribution pipe. The fixture branch to each hose bibb shall be sized on the basis of 2.5 fixture units. 9 For water supply fixture unit values related to lots within mobilehome parks in all parts of the State of California, see California Code of Regulations, Title 25, Division 1, Chapter 2, Article 5, Section 1278. For water supply fixture unit values related to lots within special occupancy parks in all parts of the State of California, see California Code of Regulations, Title 25, Division 1, Chapter 2.2, Article 5, Section 2278.

158 2025 CALIFORNIA PLUMBING CODE

WATER SUPPLY AND DISTRIBUTION

Col1	Col2	TABLE 610.4 FIXTURE UNIT TABLE FOR DETERMINING WATER PIPE AND METER SIZES	Col4	Col5	Col6	Col7	Col8	Col9	Col10	Col11	Col12	Col13	Col14	Col15	Col16	Col17
METER AND STREET SERVICE (inches)	BUILDING SUPPLY AND BRANCHES (inches)	MAXIMUM ALLOWABLE LENGTH (feet)	MAXIMUM ALLOWABLE LENGTH (feet)	MAXIMUM ALLOWABLE LENGTH (feet)	MAXIMUM ALLOWABLE LENGTH (feet)	MAXIMUM ALLOWABLE LENGTH (feet)	MAXIMUM ALLOWABLE LENGTH (feet)	MAXIMUM ALLOWABLE LENGTH (feet)	MAXIMUM ALLOWABLE LENGTH (feet)	MAXIMUM ALLOWABLE LENGTH (feet)	MAXIMUM ALLOWABLE LENGTH (feet)	MAXIMUM ALLOWABLE LENGTH (feet)	MAXIMUM ALLOWABLE LENGTH (feet)	MAXIMUM ALLOWABLE LENGTH (feet)	MAXIMUM ALLOWABLE LENGTH (feet)	MAXIMUM ALLOWABLE LENGTH (feet)
METER AND STREET SERVICE (inches)	BUILDING SUPPLY AND BRANCHES (inches)	40	60	80	100	150	200	250	300	400	500	600	700	800	900	1000
PRESSURE RANGE – 30 to 45 psi1	PRESSURE RANGE – 30 to 45 psi1	**PRESSURE RANGE

CPC § 2.0 Medium relevance — show source text
0|2.0|2.0| |4|Clothes Washer|1|5.5|3.5|3.5| |5|Combination Bath/Shower|1|5.5|5.5|5.5| |6|Dishwasher|1|0.5|1.3|1.3| |7|Kitchen Faucet|1|2.0|2.2|2.2| |8|Laundry Faucet|0|2.0|2.0|2.0| |9|Lavatory Faucet|1|2.0|1.5|1.5| |10|Shower, per head|0|4.5|2.0|2.0| |11|Water Closet, 1.28 GPF Gravity Tank|1|1.0|3.0|3.0| |12|Other Fixture 1|0|0.0|0.0|6.0| |13|Other Fixture 2|0|0.0|0.0|6.0| |14|Other Fixture 3|0|0.0|0.0|6.0| |Total Number of Fixtures|Total Number of Fixtures|6||RESET|RUN WATER DEMAND
CALCULATOR| |99th Percentile Demand Flow =|99th Percentile Demand Flow =|8.5 GPM||||

For SI units: 1 gallon per minute = 0.66 L/s, 1 gallon = 3.785 L

FIGURE 2 WATER DEMAND CALCULATOR FOR INDOOR USE AT HOME WITH SIX EFFICIENT FIXTURES (EXAMPLE 1)

Solution: Step 2 of 2 – Determine the Pipe Size of the Building Supply.

Chart A 105.1(1) for copper piping systems (from Appendix A of the UPC, shown in Figure 3) is used to determine the pipe size, based on given friction loss, given maximum allowable pipe velocity, given pipe material and the demand load computed in Step 1. In Figure 3, the intersection of the given friction loss (15 psi) (103 kPa) and the maximum allowable pipe velocity (10 ft/s) (3.05 m/s) is labeled point A. The vertical line that descends from point A to the base of the chart

intersects four nominal sizes for L-copper pipe. These intersection points are labeled B, C, D, E and correspond to pipe sizes of 1 inch (25 mm), [3] / 4 inch (20 mm), [1] / 2 inch (15 mm) and [3] / 8 inch (10 mm), respectively. A horizontal line from points B, C, D, E to the right-hand side of the chart gives maximum flow rates of 24 gpm (1.5 L/s), 12 gpm (0.757 L/s), 4.5 gpm (0.28 L/s), and 2.3 gpm (0.145 L/s), respectively. These results are summarized in Table 1 which shows that a [3] / 4 inch (20 mm) type L copper line is the minimum size that can convey the peak water demand of 8.5 gpm (0.54 L/s).

TABLE 1

PIPE SIZE OPTIONS FOR BUILDING SUPPLY

Frequently asked questions

How do I decide between using Table 610.4 and Appendix A/M methods?

Use Table 610.4 when your installation falls within the Table’s stated conditions and you have the required inputs (minimum pressure, elevation difference, developed length, and total fixture units). If those inputs are unavailable or if you prefer hydraulic/chart methods, use Appendix A (recommended rules) or Appendix M for residential calculations. § 610.4, § 610.7, § 610.5.

What pressure should I use for sizing — average or minimum?

Design on the minimum daily service pressure available where pressure fluctuates. § 610.7(5).

Do I need to include the meter’s head loss when sizing the building supply?

Yes — friction/pressure loss through the meter (and other devices) must be included in the pressure‑loss calculations. § 610.6, § 610.2.

Can the branch piping be smaller than the building supply?

Yes — but each branch must be sized using its own total fixture units and using the same method (Table 610.4 steps or Appendix methods). Also, no branch shall exceed the total demand computed for the system. § 610.9.

What is the absolute minimum I can install for building supply and fixture branches?

The code sets 3/4 inch (20 mm) as the minimum building supply size (Table 610.4 method), and Appendix M states 1/2 inch (15 mm) as the minimum fixture branch in its residential sizing method. § 610.8; Appendix M M 102.7.1.

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Sizing, Pressure and Flow Calculations

California Plumbing Code