CPC · California Plumbing Code

How are fixture units and branch sizing handled (including flushometer fixtures)?

Q: When do I use Table 610.10 instead of Table 610.3?

Use Table 610.10 for flushometer valves (water closets and urinals). Table 610.3 contains minimum branch sizes and WSFU for many fixtures, but flushometer valve FU allocations and cumulative rules come from Table 610.10 as required by § 610.10 file.

Q: Is piping to a flushometer valve allowed to be smaller than the valve inlet?

No. § 610.10 states that piping supplying a flushometer valve shall be not less in size than the valve inlet .

Q: How do I size a system that uses flushometer tanks instead of valves?

Per § 610.11 , size mains and branches serving flushometer tanks the same as you would flush‑tank water closets — they are not assigned the Table 610.10 flushometer valve FU values; use the regular WSFU/sizing methods for those tanks .

Fixture demand is expressed as fixture units (Table 610.3). Sum the FU for the fixtures a branch serves, use the Table‑610.4 method (pressure + developed length + allowable FU) to pick pipe sizes, and treat flushometer valves specially by assigning FU from Table 610.10 and making sure piping to the valve is at least the valve inlet size; flushometer tanks are sized like conventional flush tanks (see §§ 610.3, 610.9, 610.10, 610.11) filefile.

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Last reviewed: July 6, 2026

What the code requires — 2-4 sentences

The quantity of water required for each fixture is expressed as fixture units and listed in Table 610.3; total fixture units are used to size branches and the building supply per the sizing procedures (see § 610.3 and Table 610.3) . Each branch is sized by the total fixture units it serves following the Table‑610.4 method/steps in § 610.9 and § 610.8 (selection by pressure, developed length and allowable fixture‑unit capacity) . Flushometer valves are assigned special fixture‑unit values using Table 610.10 and must be treated specially when allocating loads; piping to a flushometer valve must be not smaller than the valve inlet (see § 610.10) . Where flushometer tanks are used, sizing follows the normal flush‑tank water‑closet procedures (see § 610.11) .

The single most important rule: compute total demand in fixture units from Table 610.3, treat flushometer valves using Table 610.10, and size each branch to the total fixture units it serves per § 610.9 (and follow the Table‑610.4 selection steps) .

Requirements in detail

Key definitions & where to look

Fixture units — the numeric demand values assigned to fixtures (see § 610.3 and Table 610.3) .
Flushometer valve — a valve actuator for high‑rate flushing; assigned special fixture‑unit loadings in Table 610.10 and governed by § 610.10 .
Flushometer tank — where a tank is used with flushometer equipment, size branches and mains consistent with flush‑tank procedures under § 610.11 .
Minimum fixture branch pipe size — Table 610.3 lists the minimum nominal branch pipe size for individual fixtures; those minimums must be respected when connecting fixtures .

How to determine demand and size branches (step‑by‑step)

Identify each fixture and its WSFU (water‑supply fixture units) from Table 610.3 and sum them to get the total connected load (or the total for a branch) — § 610.3 and Table 610.3 .
For flushometer valves, determine the flushometer fixture units assigned to each section (branch/main) using Table 610.10 — do this before you total the section demand (see § 610.10) .
Use the Table‑610.4 sizing method (choose pressure range, developed length, then read the allowable fixture units) and follow the selection steps in § 610.8 to select pipe size for mains/building supply; apply the same approach to branches per § 610.9 .
Ensure any piping supplying a flushometer valve is not less than the valve inlet size and that individual fixture minimum branch sizes (Table 610.3) are met — see § 610.10 and Table 610.3 file.
For flushometer tanks, size branches and mains consistent with flush‑tank water‑closet sizing procedures (see § 610.11) .

Decision‑relevant values (quick reference)

Item / decision	Typical value(s) used in sizing	Code Reference
Where fixtures’ WSFU are listed (e.g., lavatory = 1.0 WSFU)	Use the value from Table 610.3 (private/public/assembly columns)	Table 610.3 — § 610.3 file
Minimum fixture branch pipe size for a lavatory	1/2 in. (nominal)	Table 610.3 — § 610.3
Minimum fixture branch pipe size for water closet with flushometer valve	1 in. (nominal)	Table 610.3 — § 610.3
Flushometer FU assignment — 1st water closet flushometer valve	40 FU (individual)	Table 610.10 — § 610.10
Flushometer FU assignment — cumulative for 4 water closets (example)	105 FU (per Table 610.10 accumulation)	Table 610.10 — § 610.10
Flushometer FU assignment — urinals: 1st = 20 FU, 2nd = 15 FU (cumulative 35)	Use Table 610.10 values for urinals	Table 610.10 — § 610.10
Piping that serves a flushometer valve	Must be not smaller than the valve inlet	§ 610.10
Sizing branches	Branch minimum and sizing by total FU — follow § 610.9 and Table 610.4 method	§ 610.9 and § 610.8 file
Flushometer tanks	Size as for flush‑tank water closets (do not treat as flushometer valve FU)	§ 610.11

(For full listings of fixture WSFU and the table layout, consult Table 610.3 and Table 610.10 in the CPC) file.

Exceptions & special cases

Where alternative engineering methods are used (calculated friction losses, detailed hydraulic analysis), the table methods are excepted and must be acceptable to the Authority Having Jurisdiction — see § 610.13, Exception (1) .
For fixtures with continuous or long‑duration flow (e.g., outdoor irrigation, pot fillers), the code requires determining the separate gpm demand and adding that to the fixture‑unit derived demand where noted in Table 610.3 notes .
Flushometer tanks are not assigned the same fixture‑unit values as flushometer valves; instead, size their mains/branches consistent with flush‑tank water‑closets (see § 610.11) .
Minimum branch pipe sizes listed in Table 610.3 are nominal ID and must be observed for each individual fixture connection (see notes to Table 610.3) .

Common mistakes

Treating a flushometer valve like a gravity tank fixture and using the Table‑610.3 WSFU instead of Table 610.10 (Table 610.10 must be used for flushometer valves per § 610.10) .
Sizing supply piping smaller than the flushometer valve inlet — the code explicitly forbids this (see § 610.10) .
Forgetting to add continuous gpm demands (e.g., pot fillers, some hose bibbs) separately when Table notes require it (see Table 610.3 notes) .
Using the total building fixture units to size a branch that serves only a subset of fixtures — branches must be sized to the fixture units they actually serve per § 610.9 .
Assuming flushometer tanks and flushometer valves are interchangeable for sizing; § 610.11 requires tank‑served systems follow flush‑tank procedures, while § 610.10 governs valve FU assignments file.

Worked example — public restroom group (numbers)

Scenario: a single plumbing branch serves 4 water closets operated by flushometer valves, 2 urinals with flushometer valves, and 3 lavatories (public). Apply the CPC steps and tables:

Assign flushometer FUs from Table 610.10:
- Water closets (flushometer valves): 4 WCs → cumulative = 105 FU (Table 610.10 cumulative entry for 4) .
- Urinals (flushometer valves): 2 urinals → cumulative = 35 FU (1st = 20 FU, 2nd = 15 FU) .
Assign lavatory WSFU from Table 610.3: 3 lavs × 1.0 WSFU = 3 FU .
Total branch demand = 105 + 35 + 3 = 143 fixture units. (This is the total FU that the branch must be evaluated against when selecting a pipe size using the Table‑610.4 method.) .
Minimum individual branch/connect sizes: each water closet flushometer valve requires a 1‑inch minimum branch (Table 610.3) — any piping directly feeding a WC flushometer must be at least 1 in.; urinal flushometer valves have a 3/4‑inch minimum per Table 610.3 . Also, note § 610.10: piping supplying a flushometer valve shall be not less than the valve inlet .
Next step (not computed here): take the 143 FU, determine available pressure and developed length, then use Table 610.4 and the steps in § 610.8 to read the allowable fixture units for candidate pipe sizes and pick the smallest acceptable size for the branch/main; do not exceed pressure/length limits and respect minimum nominal branch sizes already noted file.

Note: I have not selected a specific pipe diameter from Table 610.4 because that selection requires the available pressure and developed length (steps and the table are in § 610.8 / Table 610.4) .

Related provisions (useful cross‑references)

§ 610.3 — Quantity of water; use Table 610.3 for fixture‑unit values (see Table 610.3) .
§ 610.9 — Size of Branches; branches are sized by total FU served and follow § 610.8 procedures .
§ 610.10 — Sizing for Flushometer Valves; Table 610.10 governs FU assignments and piping minimums for flushometer valves .
Table 610.10 — Flushometer fixture units (water closets and urinals) — used when sizing flushometer valve systems .
Table 610.3 — Water‑supply fixture units (WSFU) and minimum fixture branch sizes (full listing for common fixtures) .
§ 610.11 — Sizing systems for flushometer tanks (size as flush‑tank water closets) .
§ 610.8 and Table 610.4 — Steps and lookup table used to select meter/building supply and branch sizes once total FU, pressure and length are known (see § 610.8 for the selection steps) .
Appendix A (Sizing procedure alternative) — detailed hydraulic method for sizing where Table method is not used .

Code references

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

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 § 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 § 3.0 High relevance — show source text
0 GPF Flushometer Valve|3⁄4|3.0|4.0|5.0| |Urinal, greater than 1.0 GPF Flushometer Valve|3⁄4|4.0|5.0|6.0| |Urinal, flush tank|1⁄2|2.0|2.0|3.0| |Wash Fountain, circular spray|3⁄4|–|4.0|–| |Water Closet, 1.6 GPF Gravity Tank|1⁄2|2.5|2.5|3.5| |Water Closet, 1.6 GPF Flushometer Tank|1⁄2|2.5|2.5|3.5| |Water Closet, 1.6 GPF Flushometer Valve|1|5.0|5.0|8.0| |Water Closet, greater than 1.6 GPF Gravity Tank|1⁄2|3.0|5.5|7.0| |Water Closet, greater than 1.6 GPF Flushometer Valve|1|7.0|8.0|10.0|

For SI units: 1 inch = 25 mm

Notes: 1 Size of the cold branch pipe, or both the hot and cold branch pipes. 2 Appliances, appurtenances, or fixtures not included in this table shall be permitted to be sized by reference to fixtures having a similar flow rate and frequency of use. 3 The listed fixture unit values represent their total load on the cold water building supply. The separate cold water and hot water fixture unit value for fixtures having both cold and hot water connections shall be permitted to be three-quarters of the listed total value of the fixture. 4 The listed minimum supply branch pipe sizes for individual fixtures are the nominal (I.D.) pipe size. 5 For fixtures or supply connections likely to impose continuous flow demands, determine the required flow in gallons per minute (gpm) (L/s) and add it separately to the demand in gpm (L/s) for the distribution system or portions thereof. 6 Assembly [Public Use (see Table 422.1)]. 7 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 by 2.5 fixture units.

2025 CALIFORNIA PLUMBING CODE 369

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APPENDIX A

CHART A 103.1(1)

ESTIMATE CURVES FOR DEMAND LOAD

FIXTURE UNITS

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

CHART A 103.1(2)

ENLARGED SCALE DEMAND LOAD

FIXTURE UNITS

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

370 2025 CALIFORNIA PLUMBING CODE

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APPENDIX A

TABLE A 104.4(1) ALLOWANCE IN EQUIVALENT LENGTH OF PIPE FOR FRICTION LOSS IN VALVES AND THREADED FITTINGS*

EQUIVALENT LENGTH OF PIPE FOR VARIOUS FITTINGS
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 § 1.0 High relevance — show source text
0| |Nonwater Urinal with Drain Cleansing Action|1⁄2|1.0|1.0|1.0| |Wash Fountain, circular spray|3⁄4|––|4.0|––| |Water Closet, 1.6 GPF Gravity Tank|1⁄2|2.5|2.5|3.5| |Water Closet, 1.6 GPF Flushometer Tank|1⁄2|2.5|2.5|3.5| |Water Closet, 1.6 GPF Flushometer Valve|1|See Footnote7|See Footnote7|––| |Water Closet, greater than 1.6 GPF Gravity Tank|1⁄2|3.0|5.5|7.0| |Water Closet, greater than 1.6 GPF Flushometer Valve|1|See Footnote7|See Footnote7|––|

For SI units: 1 inch = 25 mm

Notes: 1 Size of the cold branch pipe, or both the hot and cold branch pipes. 2 Appliances, appurtenances, or fixtures not referenced in this table shall be permitted to be sized by reference to fixtures having a similar flow rate and frequency of use. 3 The listed fixture unit values represent their load on the cold water building supply. The separate cold water and hot water fixture unit value for fixtures having both hot and cold water connections shall be permitted to be each taken as three-quarter of the listed total value of the fixture. 4 The listed minimum supply branch pipe sizes for individual fixtures are the nominal (I.D.) pipe size. 5 For fixtures or supply connections likely to impose continuous flow demands, determine the required flow in gallons per minute (gpm) (L/s), and add it separately to the demand in gpm (L/s) for the distribution system or portions thereof. 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

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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
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 § 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 § 1.0 High relevance — show source text
0|–| |Dental Unit, cuspidor|1⁄2|–|1.0|–| |Dishwasher, domestic|1⁄2|1.5|1.5|–| |Drinking Fountain or Water Cooler|1⁄2|0.5|0.5|0.75| |Hose Bibb|1⁄2|2.5|2.5|–| |Hose Bibb, each additional7|1⁄2|1.0|1.0|–| |Lavatory|1⁄2|1.0|1.0|1.0| |Lawn Sprinkler, each head5|–|1.0|1.0|–| |Mobile Home, each (minimum)|–|12.0|–|–| |Sinks|–|–|–|–| |Bar|1⁄2|1.0|2.0|–| |Clinical Faucet|1⁄2|–|3.0|–| |Clinical Flushometer Valve with or without faucet|1|–|8.0|–| |Kitchen, domestic with or without dishwasher|1⁄2|1.5|1.5|–| |Laundry|1⁄2|1.5|1.5|–| |Service or Mop Basin|1⁄2|1.5|3.0|–| |Washup, each set of faucets|1⁄2|–|2.0|–| |Shower per head|1⁄2|2.0|2.0|–| |Urinal, 1.0 GPF Flushometer Valve|3⁄4|3.0|4.0|5.0| |Urinal, greater than 1.0 GPF Flushometer Valve|3⁄4|4.0|5.0|6.0| |Urinal, flush tank|1⁄2|2.0|2.0|3.0| |Wash Fountain, circular spray|3⁄4|–|4.0|–| |Water Closet, 1.6 GPF Gravity Tank|1⁄2|2.5|2.5|3.5| |Water Closet, 1.6 GPF Flushometer Tank|1⁄2|2.5|2.5|3.5| |Water Closet, 1.6 GPF Flushometer Valve|1|5.0|5.0|8.0| |Water Closet, greater than 1.6 GPF Gravity Tank|1⁄2|3.0|5.5|7.0| |Water Closet, greater than 1.6 GPF Flushometer Valve|1|7.0|8.0|10.0|

For SI units: 1 inch = 25 mm

Notes: 1 Size of the cold branch pipe, or both the hot and cold branch pipes. 2 Appliances, appurtenances, or fixtures not included in this table shall be permitted to be sized by reference to fixtures having a similar flow rate and frequency of use. 3 The listed fixture unit values represent their total load on the cold water building supply. The separate cold water and hot water fixture unit value for fixtures having both cold and hot water connections shall be permitted to be three-quarters of the listed total value of the fixture. 4 The listed minimum supply branch pipe sizes for individual fixtures are the nominal (I.D.) pipe size.
CPC § 0.5 High relevance — show source text
5|0.5|0.75| |Hose Bibb|1⁄2|2.5|2.5|––| |Hose Bibb, each additional8|1⁄2|1.0|1.0|––| |Lavatory|1⁄2|1.0|1.0|1.0| |Lawn Sprinkler, each head5|––|1.0|1.0|––| |Mobilehome or Manufactured Home, each (minimum)9|––|6.0|––|––| |Sinks|––|––|––|––| |Bar|1⁄2|1.0|2.0|––| |Clinical Faucet|1⁄2|––|3.0|––| |Clinical Flushometer Valve with or without faucet|1|––|8.0|––| |Kitchen, domestic with or without dishwasher|1⁄2|1.5|1.5|––| |Laundry|1⁄2|1.5|1.5|––| |Service or Mop Basin|1⁄2|1.5|3.0|––| |Washup, each set of faucets|1⁄2|––|2.0|––| |Shower, per head|1⁄2|2.0|2.0|––| |Urinal, 1.0 GPF Flushometer Valve|3⁄4|See Footnote7|See Footnote7|––| |Urinal, greater than 1.0 GPF Flushometer Valve|3⁄4|See Footnote7|See Footnote7|––| |Urinal, flush tank|1⁄2|2.0|2.0|3.0| |Nonwater Urinal with Drain Cleansing Action|1⁄2|1.0|1.0|1.0| |Wash Fountain, circular spray|3⁄4|––|4.0|––| |Water Closet, 1.6 GPF Gravity Tank|1⁄2|2.5|2.5|3.5| |Water Closet, 1.6 GPF Flushometer Tank|1⁄2|2.5|2.5|3.5| |Water Closet, 1.6 GPF Flushometer Valve|1|See Footnote7|See Footnote7|––| |Water Closet, greater than 1.6 GPF Gravity Tank|1⁄2|3.0|5.5|7.0| |Water Closet, greater than 1.6 GPF Flushometer Valve|1|See Footnote7|See Footnote7|––|

For SI units: 1 inch = 25 mm

Notes: 1 Size of the cold branch pipe, or both the hot and cold branch pipes. 2 Appliances, appurtenances, or fixtures not referenced in this table shall be permitted to be sized by reference to fixtures having a similar flow rate and frequency of use. 3 The listed fixture unit values represent their load on the cold water building supply. The separate cold water and hot water fixture unit value for fixtures having both hot and cold water connections shall be permitted to be each taken as three-quarter of the listed total value of the fixture. 4 The listed minimum supply branch pipe sizes for individual fixtures are the nominal (I.D.) pipe size. 5 For fixtures or supply connections likely to impose continuous flow demands, determine the required flow in gallons per minute (gpm) (L/s), and add it separately to the demand in gpm (L/s) for the distribution system or portions thereof.
CPC § 304.3.1 Medium relevance — show source text
be sized based on the total accumulated connected load at each story or branch interval.

C 304.3.1 Horizontal Stack Offsets. Horizontal

stack offsets shall be sized in accordance with Table C 304.2 as required for building drains.

C 304.3.2 Vertical Stack Offsets. Vertical stack off sets shall be sized in accordance with Table C 304.3 as required for stacks.

C 304.4 Horizontal Stack Offset and Horizontal Branch

Connections. Horizontal branch connections shall not connect to a horizontal stack offset or within 2 feet (610 mm) above or below the offset where such horizontal offset is located more than four branch intervals below the top of the stack.

C 401.0 Vent System Sizing. C 401.1 Size of Vents. The size of vent piping shall be determined from the developed length and the total number of drainage fixture units connected in accordance with Table C 401.1. Vents shall be not less than one-half the required size of the drainage pipe size served as determined by Table C 304.3 for horizontal fixture branches and stacks nor less than 1 [1] ⁄ 4 inches

(32 mm) in diameter. The drainage system shall be vented by not less than one vent pipe which shall be not less than one-half the size of the required building drain and which shall extend from the building drain or extension of building drain to the outdoors. Vents shall be installed in accordance with Chapter 9. C 401.2 Vent Stack. A vent stack shall be required for a drainage stack that extends five or more branch intervals above the building drain or horizontal branch. The developed length of the vent stack shall be measured from the lowest connection of a branch vent to the termination outdoors.

C 401.3 Branch Vents. Where branch vents exceed 40 feet (12 192 mm) in developed length, such vent shall be increased by one pipe size for the entire developed length of the vent pipe. C 401.4 Venting Horizontal Offsets. Drainage stacks with horizontal offsets shall be vented where five or more branch intervals are located above the offset. The upper and lower section of the horizontal offset shall be vented in accordance

with Section C 401.4.1 and Section C 401.4.2.

C 401.4.1 Venting Upper Section. The vent for the upper section of the stack shall be vented as a separate stack with a vent stack connection installed at the base of the drainage stack. Such vent stack shall connect below the lowest horizontal branch or building drain. Where vent stack connects to the building drain, the connection shall be located downstream of the drainage stack and within a distance of 10 times the diameter of the drainage stack. C 401.4.2 Venting Lower Section. The vent for the lower section of the stack shall be vented by a yoke vent connecting between the offset and the next lower horizontal branch using a wye-branch fitting. The size of the yoke vent and connection shall be not less in diameter

388 2025 CALIFORNIA PLUMBING CODE

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

APPENDIX C

TABLE C 303.3 DRAINAGE FIXTURE UNIT VALUES (DFU) FOR BATHROOM GROUPS [1, 2]
CPC § 502.7 Medium 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.

508 2025 CALIFORNIA PLUMBING CODE

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

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 § 4.5 High relevance — show source text
0|4.5|4.1|4.1| |Each Additional1⁄2 Bath|0.5|0.1|0.4|0.4| |Each Additional Bathroom Group|1.0|0.5|0.8|0.8| |Other Groups of Fixtures|Other Groups of Fixtures|Other Groups of Fixtures|Other Groups of Fixtures|Other Groups of Fixtures| |Bathroom Group (1.6 GPF Flushometer Value)|6.0|2.5|4.0|1.7| |Kitchen Group (Sink and Dishwasher)|2.0|2.0|1.5|1.5| |Laundry Group (Sink and Clothes Washer)|5.0|5.0|3.0|3.0|

Notes: 1 A bathroom group, for this table, consists of one water closet, up to two lavatories, and either one bathtub or one shower. 2 A half-bath or powder room, for this table, consists of one water closet and one lavatory. 3 Multi-unit dwellings with individual water heaters use the same WSFU as for individual dwellings.

C 304.2 Size of Building Drain and Building Sewer. The maximum number of drainage fixture units allowed on the building drain or building sewer of a given size shall be in accordance with Table C 304.2. The size of a building drain or building sewer serving a water closet shall be not less than 3 inches (80 mm).

C 304.3 Size of Horizontal Branch or Vertical Stack. The maximum number of drainage fixture units allowed on a horizontal branch or vertical soil or waste stack of a given size shall be in accordance with Table C 304.3. Stacks shall

be sized based on the total accumulated connected load at each story or branch interval.

C 304.3.1 Horizontal Stack Offsets. Horizontal

stack offsets shall be sized in accordance with Table C 304.2 as required for building drains.

C 304.3.2 Vertical Stack Offsets. Vertical stack off sets shall be sized in accordance with Table C 304.3 as required for stacks.

C 304.4 Horizontal Stack Offset and Horizontal Branch

Connections. Horizontal branch connections shall not connect to a horizontal stack offset or within 2 feet (610 mm) above or below the offset where such horizontal offset is located more than four branch intervals below the top of the stack.

C 401.0 Vent System Sizing. C 401.1 Size of Vents. The size of vent piping shall be determined from the developed length and the total number of drainage fixture units connected in accordance with Table C 401.1. Vents shall be not less than one-half the required size of the drainage pipe size served as determined by Table C 304.3 for horizontal fixture branches and stacks nor less than 1 [1] ⁄ 4 inches

(32 mm) in diameter. The drainage system shall be vented by not less than one vent pipe which shall be not less than one-half the size of the required building drain and which shall extend from the building drain or extension of building drain to the outdoors. Vents shall be installed in accordance with Chapter 9. C 401.2 Vent Stack. A vent stack shall be required for a drainage stack that extends five or more branch intervals above the building drain or horizontal branch. The developed length of the vent stack shall be measured from the lowest connection of a branch vent to the termination outdoors.

CPC § 422.1 High 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.

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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 § 105.1 High relevance — show source text

** 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. For extremely hard water, it will be advisable to make additional allowances for the reduction of the capacity of hot-water lines in service.

A 106.0 Size of Principal Branches and Risers. A 106.1 Size. The required size of branches and risers shall be permitted to be obtained in the same manner as the building supply, by obtaining the demand load on each branch or riser and using the permissible friction loss computed in Section A 104.0. A 106.2 Branches. Where fixture branches to the building supply are sized for the same permissible friction loss per 100 feet (30 480 mm) of pipe as the branches and risers to the

highest level in the building and lead to the inadequate water supply to the upper floor of a building, one of the following shall be provided: (1) Selecting the sizes of pipe for the different branches so that the total friction loss in each lower branch is approximately equal to the total loss in the riser, including both friction loss and loss in static pressure.

(2) Throttling each such branch using a valve until the preceding balance is obtained.

(3) Increasing the size of the building supply and risers above the minimum required to meet the maximum permissible friction loss.

A 106.3 Water Closets. The size of branches and mains serving flushometer tanks shall be consistent with sizing procedures for flush tank water closets.

A 107.0 General.

A 107.1 Velocities. Velocities shall not exceed 10 feet per second (ft/s) (3 m/s), except as otherwise approved by the Authority Having Jurisdiction. A 107.2 Pressure-Reducing Valves. Where a pressurereducing valve is used in the building supply, the developed length of supply piping and the permissible friction loss shall be computed from the building side of the valve. A 107.3 Fittings. The allowances in Table A 104.4(1) for fittings are based on non-recessed threaded fittings. For recessed threaded fittings and streamlined soldered fittings, one-half of the allowances given in the table will be ample.

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APPENDIX A

TABLE A 103.1 WATER SUPPLY FIXTURE UNITS (WSFU) AND MINIMUM FIXTURE BRANCH PIPE SIZES [3]

APPLIANCES, APPURTENANCES, OR FIXTURES2	MINIMUM FIXTURE BRANCH PIPE SIZE1,4 (inches)	PRIVATE	PUBLIC	ASSEMBLY6
Bathtub or Combination Bath/Shower (fill)	1⁄2	4.0	4.0	–
3⁄4 inch Bathtub Fill Valve	3⁄4	10.0	10.0	–
Bidet	1⁄2	1.0	–	–
Clothes Washer	1⁄2	4.0	4.0	–
Dental Unit,

Frequently asked questions

Can I just add up Table 610.3 values and pick a pipe size directly from that total?

You must add Table 610.3 fixture units to get total connected load, but to select pipe size you must follow the Table‑610.4 method (pressure range + developed length + allowable FU) and the steps in § 610.8/§ 610.9 rather than pick a size directly from Table 610.3 alone file.

When do I use Table 610.10 instead of Table 610.3?

Use Table 610.10 for flushometer valves (water closets and urinals). Table 610.3 contains minimum branch sizes and WSFU for many fixtures, but flushometer valve FU allocations and cumulative rules come from Table 610.10 as required by § 610.10 file.

Is piping to a flushometer valve allowed to be smaller than the valve inlet?

No. § 610.10 states that piping supplying a flushometer valve shall be not less in size than the valve inlet .

How do I size a system that uses flushometer tanks instead of valves?

Per § 610.11, size mains and branches serving flushometer tanks the same as you would flush‑tank water closets — they are not assigned the Table 610.10 flushometer valve FU values; use the regular WSFU/sizing methods for those tanks .

What if my project uses a hydraulic calculation rather than tables?

The code allows engineered hydraulic methods acceptable to the Authority Having Jurisdiction as exceptions to the table method (see § 610.13, Exception (1)); follow recognized engineering procedures and document friction‑loss computations and assumptions .

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