CPC · California Plumbing Code

Minimum pipe sizing, mains, branches and drops to station outlets

Q: What is the minimum pipe size I can use for a station outlet drop?

The code requires a minimum of DN15 (NPS 1/2) for drops to individual station outlets/inlets per §1323.1.2 .

Q: Can I use DN8 tubing for station drops if the outlet rarely used?

No. DN8 runouts are permitted only for alarm panels and instrument tubing per §1323.1.3 ; station drops must be at least DN15 as required by §1323.1.2 .

Q: If my system has 20 outlets, do I automatically stay at minimum DN15?

Not necessarily. While DN15 is the minimum per §1323.1.1–.2 , a full sizing calculation per §1323.1.5 (using Table 1305.2 flows, diversity from Table 1323.1.5(1), equivalent length and pressure‑drop tables) may show a larger pipe is required. file

Q: Where do I find the allowable pressure loss to each outlet?

The allowable maximum system pressure loss values are in Table 1323.1.5(2) (example: Oxygen and Medical Air = 5 psi ; Medical Vacuum = 4 inHg ). The sizing procedure requires that total loss to each outlet not exceed those values.

The California Plumbing Code requires medical gas and vacuum piping be sized to deliver required flows at allowable pressures. Minimum sizes are DN15 (½") for gas mains/branches and drops, and DN20 (¾") minimum for vacuum mains/branches. If system demand falls within the CPC tables, follow the code’s sizing steps (use per‑outlet flows, apply a 1.5 equivalent‑length multiplier, use diversity factors and pressure‑drop tables) and ensure total pressure loss to each outlet does not exceed the permitted limits in the code. file

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Last reviewed: July 6, 2026

What the code requires — plain English

Piping for medical gas and vacuum systems must be sized to deliver the required flow rates at the utilization pressures — that is the controlling rule in §1323.1.
The code sets minimum nominal sizes for distribution piping: mains and branches and drops to individual station outlets (see §1323.1.1 and §1323.1.2).
Where system demand falls within the tabulated ranges the code requires using the prescribed sizing procedure and maximum allowable pressure loss limits (see §1323.1.4).

The single most important rule: design and size medical gas/vacuum piping to meet the required flow at the permitted pressure loss — and never use a pipe smaller than the minimum sizes the code prescribes. (See §1323.1, §1323.1.1, §1323.1.2, §1323.1.4.)

Requirements in detail

Key minimum sizes (code references)

System element	Minimum size (nominal / O.D.)	Code Reference
Mains and branches — medical gas	DN15 (NPS 1/2) — (5/8 inch O.D.) — minimum	§1323.1.1
Mains and branches — medical‑surgical vacuum	DN20 (NPS 3/4) — (7/8 inch O.D.) — minimum	§1323.1.1
Drops to individual station outlets / inlets	DN15 (NPS 1/2) — (5/8 inch O.D.) — minimum	§1323.1.2

Notes:

The requirement that "piping systems shall be designed and sized to deliver the required flow rates at the utilization pressures" is the overarching mandate in §1323.1.
Minimum sizes are absolute lower limits in the code; do not reduce sizes below these values for the listed piping categories.

Sizing when demand is within tabulated ranges

If the system's maximum demand falls within the ranges covered by the code tables, pipe sizing shall be performed using the code’s sizing procedure (start with Tables 1323.1.4(1)–1323.1.4(6) and follow Section §1323.1.5). The rule that determines whether you use the tabulated method is §1323.1.4.
For demand beyond the tables' range, the code requires standard engineering methods acceptable to the Authority Having Jurisdiction (see §1323.1.6).

What the sizing procedure requires (summary of steps)

When using the tabulated method (see §1323.1.5):

Determine flows per outlet from Table 1305.2 (code) and total number of outlets.
Convert measured pipe length to an equivalent length by multiplying the measured length by 1.5 (150%) to account for fittings.
Apply the diversity factor for the number of outlets from Table 1323.1.5(1) to get the sizing flow rate. Table 1323.1.5(1) and its minimum system flows are in the code.
Use the pressure‑drop tables (Tables 1323.1.4(1)–(6) — choose the table for the specific gas or vacuum) to find pressure loss per 100 ft for candidate pipe sizes; multiply by the equivalent length and sum downstream losses. The total system pressure loss to each outlet must not exceed the values in Table 1323.1.5(2). file

Important numeric thresholds from the code

Diversity percentages and minimum permissible system flows (excerpts in Table 1323.1.5(1)): for 1–10 outlets = 100% (actual demand); 11–25 outlets = 75%, minimum permissible system flow 7.0 SCFM; 26–50 outlets = 50%, minimum 13.1 SCFM; etc.
Maximum permitted system pressure loss examples (from Table 1323.1.5(2)): Medical Air = 5 psi, Oxygen = 5 psi, Nitrogen = 15 psi, Medical Vacuum = 4 inHg (code tables list these by system). Use these limits when summing pressure drops.

Exceptions & special cases

If system maximum demand does not fall within the ranges in Tables 1323.1.4(1)–(6), the code requires engineering methods acceptable to the Authority Having Jurisdiction under §1323.1.6 (i.e., the tabulated method is not applicable). §1323.1.4 directs which method to use. file
The minimum sizes in §1323.1.1 and §1323.1.2 are absolute lower limits. Larger sizes are required where the sizing procedure (or engineering calculation) shows they are necessary to meet flow/pressure requirements.
The code permits smaller tubing for runouts to gauges/alarm devices (DN8) per §1323.1.3, but that applies only to those specific uses — do not apply that exception to station drops.

Common mistakes

Assuming the minimum nominal size (DN15) is always acceptable: the minimum is only a lower limit — the sizing procedure or engineering calculation may require larger pipe to meet flow and pressure loss limits (see §1323.1, §1323.1.4).
Failing to use the 150% equivalent length multiplier for fittings when calculating pressure drop (a required step in §1323.1.5) — this underestimates friction loss and leads to undersized piping.
Ignoring the maximum permitted system pressure loss (Table 1323.1.5(2)) when summing section losses to each outlet; exceedance means the design does not comply.
Using runout/run‑tubing sizes intended for instruments (DN8) as a justification to reduce station drops or distribution mains — those smaller sizes are limited to runouts and instrument connections by the code.

Worked example — applying the rule (walkthrough with code references)

Scenario: a medical oxygen piping system with 20 station outlets; central source located in plant room; you need to verify minimum sizes and whether the tabulated sizing method applies.

Minimum-size check:
- Mains/branches minimum for medical gas = DN15 (NPS 1/2). Therefore, do not specify any mains or branches smaller than DN15; drops to individual outlets must be at least DN15 as well. See §1323.1.1 and §1323.1.2.
Does the tabulated sizing method apply?
- With 20 outlets, consult Table 1323.1.5(1): 11–25 outlets → diversity 75% and minimum permissible system flow = 7.0 SCFM. This means the system falls within the tabulated range and you must use the sizing procedure in §1323.1.5.
Follow the sizing procedure (code steps; exact numeric results require additional tables):
- Determine per‑outlet flow from Table 1305.2 (not reproduced here). Multiply per‑outlet flow by 20 outlets and then by the 75% diversity to get the sizing flow. (The code explicitly requires using Table 1305.2 and Table 1305.3 to determine individual outlet flows; see §1323.1.5.)
- Measure each section length and multiply by 1.5 to get the equivalent length (to account for fittings). §1323.1.5 requires this equivalent‑length step.
- Choose a candidate pipe size (no smaller than the DN15 minimum) and read the pressure drop per 100 ft for that gas and pipe size from Tables 1323.1.4(1)–(6) (choose the oxygen table). Multiply the per‑100‑ft pressure drop by the equivalent length and divide by 100 to get the section loss; sum losses from source to each outlet. The total must not exceed the allowable loss for oxygen (5 psi from Table 1323.1.5(2)). file

Important: I cannot finish the numeric pressure‑loss arithmetic here because the code requires looking up:

per‑outlet SCFM in Table 1305.2, and
pressure‑drop values per 100 ft for oxygen in Table 1323.1.4(4) (or the applicable table for the gas).
Those specific tables are part of the CPC; to complete the calculation you must read the values from those tables and then apply the arithmetic steps in §1323.1.5. file

Related provisions (quick pointer list)

§1323.1 — Required pipe sizing, overall design mandate.
§1323.1.1 — Minimum nominal sizes for mains and branches.
§1323.1.2 — Minimum size for drops to individual station outlets/inlets.
§1323.1.3 — Runouts and connecting tubing (allowed DN8 for gauges/alarm runouts).
§1323.1.4 — When to use tabulated sizing method vs. engineering methods.
§1323.1.5 — Step‑by‑step sizing procedure, diversity table, equivalent‑length multiplier and maximum allowed system pressure loss (Tables 1323.1.5(1) & (2)). file
§1323.1.6 — Engineering methods for systems outside tabulated ranges.
§1305.2 / §1305.3 — Tables with the flow rates assigned to station outlets/inlets used in the sizing procedure (referenced by §1323.1.5).

Code references

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

CPC § 1322.6.1 High relevance — show source text
1322.6.1 Dielectric Fittings. Dielectric fittings that comply with the following shall be permitted only where required by the manufacturer of special medical equipment to electrically isolate the equipment from the system distribution piping:

(1) They shall be of brass or copper construction with an approved dielectric.

(2) They shall be permitted to be a union.

(3) They shall be clean for oxygen where used for medical gases and medical support gases. [NFPA 99:5.1.10.9.2]

1322.7 Prohibited Joints. The following joints shall be prohibited throughout medical gas and vacuum distribution pipeline systems:

(1) Flared and compression-type connections, including connections to station outlets and inlets, alarm devices, and other components.

(2) Other straight-threaded connections, including unions.

(3) Pipe-crimping tools used to permanently stop the flow of medical gas and vacuum piping.

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HEALTH CARE FACILITIES AND MEDICAL GAS AND MEDICAL VACUUM SYSTEMS

(4) Removable and nonremovable push-fit fittings that employ a quick assembly push fit connector. [NFPA 99:5.1.10.10]

1323.0 Installation of Piping and Equipment. 1323.1 Required Pipe Sizing. Piping systems shall be designed and sized to deliver the required flow rates at the utilization pressures. [NFPA 99:5.1.10.11.1.1]

1323.1.1 Mains and Branches. Mains and branches in medical gas piping systems shall be not less than DN15 (NPS [1] ⁄ 2 ) ( [5] ⁄ 8 inch O.D.) size. Mains and branches in medical-surgical vacuum systems shall be not less than DN20 (NPS [3] ⁄ 4 ) ( [7] ⁄ 8 inch O.D.) size. [NFPA 99:5.1.10.11.1.2, 5.1.10.11.1.3] 1323.1.2 Drops to Individual Stations. Drops to individual station outlets and inlets shall be not less than DN15 (NPS [1] ⁄ 2 ) ( [5] ⁄ 8 inch O.D.) size. [NFPA 99:5.1.10.11.1.4] 1323.1.3 Runouts and Connecting Tubing. Runouts to alarm panels and connecting tubing for gauges and alarm devices shall be permitted to be DN8 (NPS [1] ⁄ 4 ) ( [3] ⁄ 8 inch O.D.) size. [NFPA 99:5.1.10.11.1.5]

1323.1.4 Maximum Demand. Where the maximum demand for each medical gas or vacuum system does not exceed the values in Table 1323.1.4(1) through Table 1323.1.4(6), the size of pipe of each section of the system shall be determined in accordance with Section 1323.1.5. The size for systems beyond the range of Table 1323.1.4(1) through Table 1323.1.4(6) shall be determined in accordance with Section 1323.1.6.

CPC § 1323.1.4 High relevance — show source text

1323.1.4 Maximum Demand. Where the maximum demand for each medical gas or vacuum system does not exceed the values in Table 1323.1.4(1) through Table 1323.1.4(6), the size of pipe of each section of the system shall be determined in accordance with Section 1323.1.5. The size for systems beyond the range of Table 1323.1.4(1) through Table 1323.1.4(6) shall be determined in accordance with Section 1323.1.6.

1323.1.5 Sizing Procedures. The size of each section of pipe in a system within the range of Table 1323.1.4(1) through Table 1324.1.4(6) shall be determined in accordance with the following:

(1) Determine the total flow rate and number of outlets or inlets for each section of pipe in accordance with Table 1305.2 and Table 1305.3.

(2) Measure the length of the section of pipe to each station outlet or inlet on the system. Multiply the measured pipe length by 1.5 (150 percent), to account for the number of fittings in the system, to determine the pipe equivalent length.

(3) Beginning with the most remote outlet or inlet, multiply the total flow rate by the diversity factor specified in Table 1323.1.5(1) for each section of pipe to determine the sizing flow rate for the piping.

(4) Select Table 1323.1.4(1) through Table 1324.1.4(6) based on the medical gas or vacuum being transported through the piping.

(5) Select an estimated pipe size for determining the system pressure loss. Multiply the pipe equivalent length, for a given section of pipe, by the pressure loss for the sizing flow rate in the applicable table. Divide that number by 100 to determine the system pressure loss for the section of pipe.

(6) Add the pressure loss for each section of piping, from the source equipment location to the outlet or

inlet, to determine the total system pressure loss to each outlet or inlet. The total system pressure loss in the piping to each outlet or inlet shall not exceed the values specified in Table 1323.1.5(2).

TABLE 1323.1.5(1) SYSTEM SIZING – FLOW REQUIREMENTS FOR STATION OUTLETS AND INLETS [1]

NUMBER OF OUTLETS AND INLETS TERMINAL UNITS PER FACILITY	DIVERSITY PERCENTAGE OF AVERAGE FLOW PER OUTLETS AND INLETS TERMINAL UNITS	MINIMUM PERMISSIBLE SYSTEM FLOW OF ALL PRESSURIZED MEDICAL GAS SYSTEMS2 (standard cubic feet per minute)
1–10	100%	Actual Demand
11–25	75%	7.0
26–50	50%	13.1
51–100	50%	17.5

Notes: 1 Flow rates of station outlets and inlets in accordance with Table 1305.2. 2 The minimum system flow is the average outlets and inlets flow times the number of station outlets and inlets times the diversity percentage.

TABLE 1323.1.5(2) MAXIMUM PERMITTED PRESSURE LOSS IN

CPC § 1323.1.5 High relevance — show source text

(6) Add the pressure loss for each section of piping, from the source equipment location to the outlet or

TABLE 1323.1.5(1) SYSTEM SIZING – FLOW REQUIREMENTS FOR STATION OUTLETS AND INLETS [1]

NUMBER OF OUTLETS AND INLETS TERMINAL UNITS PER FACILITY	DIVERSITY PERCENTAGE OF AVERAGE FLOW PER OUTLETS AND INLETS TERMINAL UNITS	MINIMUM PERMISSIBLE SYSTEM FLOW OF ALL PRESSURIZED MEDICAL GAS SYSTEMS2 (standard cubic feet per minute)
1–10	100%	Actual Demand
11–25	75%	7.0
26–50	50%	13.1
51–100	50%	17.5

TABLE 1323.1.5(2) MAXIMUM PERMITTED PRESSURE LOSS IN

MEDICAL GAS AND MEDICAL VACUUM SYSTEMS

TYPE OF SYSTEM	MAXIMUM ALLOWABLE SYSTEM PRESSURE LOSS (psi)
Medical Air	5
Nitrogen	15
Nitrous Oxide	5
Carbon Dioxide	5
Oxygen	5
Medical Vacuum	4 inches of mercury

For SI units: 1 pound-force per square inch = 6.8947 kPa, 1 inch of mercury = 3.386 kPa

1323.1.6 Engineering Methods. For conditions other than those covered by Section 1323.1.4, such as longer runs of greater gas or vacuum demands, the size of each medical gas or vacuum piping system shall be determined by standard engineering methods acceptable to the Authority Having Jurisdiction, and each system shall be so designed that the total pressure drop or gain between the source equipment and an outlet or inlet shall not exceed the allowable pressures shown in Table 1305.1. 1323.2 Pipe Protection. Piping shall be protected against freezing, corrosion, and physical damage. [NFPA 99:5.1.10.11.2] 1323.2.1 Exposed Piping. Piping exposed in corridors and other areas where subject to physical damage from the movement of carts, stretchers, portable equipment, or vehicles shall be protected. [NFPA 99:5.1.10.11.2.1] 1323.2.2 Underground Piping. Piping underground within buildings or embedded in concrete floors or walls shall be installed in a continuous conduit. [NFPA 99:5.1.10.11.2.2]

TABLE 1323.1.5(1) SYSTEM SIZING – FLOW REQUIREMENTS FOR STATION OUTLETS AND INLETS [1]

CPC § 1322.0 High relevance — show source text
1322.0 Welded Joints . . . . . . . . . . . . . . . .288

1322.1 Welded Joints Procedure . . . . . . .288

1322.2 Welding for Stainless Tube . . . . .288

1322.3 Memory Metal Fittings . . . . . . . . .288

1322.4 Axially Swaged Fittings . . . . . . . .288

1322.5 Threaded Fittings . . . . . . . . . . . . .288

1322.6 Other Types of Fittings . . . . . . . . .288

1322.7 Prohibited Joints . . . . . . . . . . . . . .288

1323.0 Installation of Piping and Equipment . . . . . . . . . . . . . . . . . .289

1323.1 Required Pipe Sizing . . . . . . . . . .289

Table 1323.1.5(1) System Sizing – Flow Requirements for Station Outlets and Inlets . . . . . . . . . . . . .289

Table 1323.1.5(2) Maximum Permitted Pressure Loss In Medical Gas and

Medical Vacuum Systems . . . . . . .289

1323.2 Pipe Protection . . . . . . . . . . . . . . .289

Table 1323.1.4(1) Pressure Loss for Medical Air . . . . .290

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TABLE OF CONTENTS

Table 1323.1.4(2) Pressure Loss for Nitrogen . . . . . . .290

Table 1323.1.4(3) Pressure Loss for Nitrous Oxide and Carbon Dioxide . . . . . . .291

Table 1323.1.4(4) Pressure Loss for Oxygen . . . . . . .291

Table 1323.1.4(5) Pressure Loss for Vacuum . . . . . . .292

Table 1323.1.4(6) Pressure Loss for Vacuum (Category 3) . . . . . . . . . . . . . . . . . . .292

1323.3 Location of Piping . . . . . . . . . . . . .293

1323.4 Pipe Support . . . . . . . . . . . . . . . . .293

Table 1323.4.4 Maximum Pipe Support Spacing . . . . . . . . . . . . . . . . . . . . . .293

1323.5 Frost Protection . . . . . . . . . . . . . .293

1323.6 Connectors . . . . . . . . . . . . . . . . . .294

1323.7 Prohibited System Interconnections . . . . . . . . . . . . . .294

1323.8 Manufacturer’s Instructions . . . . .294

1323.9 Changes in System Use . . . . . . . .294

1323.10 Qualifications of Installers . . . . . .294

1323.11 Qualification of Brazing Procedures and Brazing . . . . . . . .295

1323.12 Breaching or Penetrating Medical Gas Piping . . . . . . . . . . .295
CPC § 1320.0 High relevance — show source text
Systems . . . . . . . . . . . . . . . . . . . .285

1320.0 Joints and Connections . . . . . . . .286

1320.1 General . . . . . . . . . . . . . . . . . . . . .286

1320.2 Changes in Direction . . . . . . . . . .286

1321.0 Brazed Joints . . . . . . . . . . . . . . . .286

1321.1 Brazed Joints and Fittings . . . . . .286

1321.2 Tube Joints . . . . . . . . . . . . . . . . . .286

1321.3 Filler Metals . . . . . . . . . . . . . . . . .286

1321.4 Copper-to-Copper Joints . . . . . . .286

1321.5 Accessible . . . . . . . . . . . . . . . . . .286

1321.6 Purging . . . . . . . . . . . . . . . . . . . . .286

1321.7 Tube Ends . . . . . . . . . . . . . . . . . .286

1321.8 Cleaning Procedures . . . . . . . . . .286

1321.9 Brazing Dissimilar Metals . . . . . . .287

1321.10 Nitrogen Purge . . . . . . . . . . . . . . .287

1321.11 Assembling and Heating Brazed Joints . . . . . . . . . . . . . . . .287

1321.12 Inspection of Brazed Joints . . . . .287

1322.0 Welded Joints . . . . . . . . . . . . . . . .288

1322.1 Welded Joints Procedure . . . . . . .288

1322.2 Welding for Stainless Tube . . . . .288

1322.3 Memory Metal Fittings . . . . . . . . .288

1322.4 Axially Swaged Fittings . . . . . . . .288

1322.5 Threaded Fittings . . . . . . . . . . . . .288

1322.6 Other Types of Fittings . . . . . . . . .288

1322.7 Prohibited Joints . . . . . . . . . . . . . .288

1323.0 Installation of Piping and Equipment . . . . . . . . . . . . . . . . . .289

1323.1 Required Pipe Sizing . . . . . . . . . .289

Table 1323.1.5(1) System Sizing – Flow Requirements for Station Outlets and Inlets . . . . . . . . . . . . .289

Table 1323.1.5(2) Maximum Permitted Pressure Loss In Medical Gas and

Medical Vacuum Systems . . . . . . .289

1323.2 Pipe Protection . . . . . . . . . . . . . . .289

Table 1323.1.4(1) Pressure Loss for Medical Air . . . . .290

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TABLE OF CONTENTS
CPC § 1304.3 Medium relevance — show source text
Construction documents . . . . . . . . . . . . . . . . . . .1304.3

Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .215.0

Health Care Facilities (OSHPD) . . . . . . . . . . . .1304.1.1 Installation requirements . . . . . . . . . . . .1304.0, 1323.0

Joints and connections . . . . . . . . . . . . . . . . . . . .1320.0

Labeling and identification . . . . . . . . . . . . . . . . .1323.13

Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1318.0

Medical air systems . . . . . . . . . . . . . . . . . . . . . . .1312.0 Medical vacuum systems . . . . . . . . . . . . . . . . . . .1319.0 Pipe sizing . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1323.1, Table 1323.1.4(1) – Table 1323.1.4(6) Pressure-regulating equipment . . . . .1308.0, 1321.10.2

Shutoff valves . . . . . . . . . . . . . . . . . . . . . . . . . . .1318.1

Source System . . . . . . . . . . . . . . . . . . . . . . . . .1304.1.2 Station outlets/inlets . . . . . . . . . . . . . . . . . . . . . .1305.3,

1314.10, 1315.0

Sterilizers and bedpan steamers . . . . . . . . . . . . .1303.4 System certification . . . . . . . . . . . . . . . . . . . . . . .1306.0 Testing and inspection . . . . . . . . . . . . . . . . . . . . .1324.0 Warning system . . . . . . . . . . . . . . . . . . . . . . . . . .1317.0 METALS, INTERMIXING PROHIBITED . . . . . .310.6, 604.1

METER, DEFINITION . . . . . . . . . . . . . . . . . . . . . . . . . . 215.0

METERING FAUCETS . . . . . . . . . . .407.2.4, 407.2.4.1, 417.1.2

MID-STORY GUIDE, DEFINITION . . . . . . . . . . . . . . . .215.0

MINIMUM STANDARDS . . . . . . . . . . . . . . . . . . . . . . . .301.2

MINIMUM PLUMBING

FACILITIES . . . . . . . . . . . . . . . . . .Table 422.1, Table 4-2,

CPC § 6.8947 Medium relevance — show source text

For SI units: 1 pound-force per square inch = 6.8947 kPa, 1 inch of mercury = 3.386 kPa

TABLE 1323.1.5(1) SYSTEM SIZING – FLOW REQUIREMENTS FOR STATION OUTLETS AND INLETS [1]

TABLE 1323.1.5(2) MAXIMUM PERMITTED PRESSURE LOSS IN

MEDICAL GAS AND MEDICAL VACUUM SYSTEMS

For SI units: 1 pound-force per square inch = 6.8947 kPa, 1 inch of mercury = 3.386 kPa

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HEALTH CARE FACILITIES AND MEDICAL GAS AND MEDICAL VACUUM SYSTEMS

TABLE 1323.1.4(1) PRESSURE LOSS FOR MEDICAL AIR

TABLE 1323.1.4(2) PRESSURE LOSS FOR NITROGEN

FLOW RATE (SCFM)1	PRESSURE DROP (psi) PER 100 FEET2	Col3	Col4
FLOW RATE (SCFM)1	1⁄2 INCH PIPE	3⁄4 INCH PIPE	1 INCH PIPE
0.35	0.004	0.001	–
0.71	0.012	0.003	–
1.06	0.023	0.005	–
1.41	0.037	0.007	–
1.77	0.055	0.011	–
2.12	0.075	0.015	–
2.47	0.097	0.019	–
2.82	0.123	0.024	–
3.18	0.

CPC § 105.1 Medium 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.

368 2025 CALIFORNIA PLUMBING CODE

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,

CPC § 609.4 Medium 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 § 504.4 Medium relevance — show source text
E 504.4 Pipe Sizes. The minimum diameters of drainage laterals, branches, and mains serving recreational vehicle sites shall be in accordance with Table E 504.4.

TABLE E 504.4

PIPE SIZES

MAXIMUM NUMBER OF
RECREATIONAL VEHICLE
STANDS SERVED MINIMUM PIPE SIZES
(inches)

5 3

36 4

71 5

120 6

440 8

For SI units: 1 inch = 25 mm

E 504.5 Cleanouts. Cleanouts shall be provided in accordance with Chapter 7 of this code. E 504.6 Drainage Inlet. Where provided, the site drainage system inlet connections for individual recreational vehicles shall be located to prevent damage by the parking of recreational vehicles or automobiles and shall consist of a sewer riser extending vertically to grade. The minimum diameter of the sewer riser pipe shall be not less than 3 inches (80 mm) in diameter, and shall be provided with a 4 inch (100 mm) inlet or not less than a 3 inch (80 mm) female fitting. E 504.6.1 Location. Where provided, the sewer inlet to individual recreational vehicle sites shall be located on the left rear half of the site (left side of the recreational vehicle) within 4 feet (1219 mm) of the stand. E 504.6.2 Protection. The sewer riser pipe shall be firmly imbedded in the ground and protected against damage from movement. It shall be provided with a tight-fitting plug or cap, which shall be secured by a durable chain (or equivalent) to prevent loss.

E 505.0 Recreational Vehicle Park Sanitary Disposal Stations.

E 505.1 Where Required. One recreational vehicle sanitary disposal station shall be provided for each 100 recreational vehicle sites, or part thereof, which are not equipped with individual drainage system connections.

E 505.2 Access. Each station shall be level and convenient of access from the service road and shall provide easy ingress and egress for recreational vehicles. E 505.3 Construction. Unless other approved means are used, each station shall have a concrete slab with the drainage

TABLE E 504.4

PIPE SIZES

For SI units: 1 inch = 25 mm

414 2025 CALIFORNIA PLUMBING CODE

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APPENDIX E

system inlet located to be on the road (left) side of the recreational vehicle. The slab shall be not less than 3 feet by 3 feet (914 mm by 914 mm), not less than 3 [1] ⁄ 2 inches (89 mm) thick and properly reinforced. The slab surface is to be troweled to a smooth finish and sloped from each side inward to a drainage system inlet.

The drainage system inlet shall consist of a 4 inch (102 mm), self-closing, foot-operated hatch of approved material with the cover milled to fit tight. The hatch body shall be set in the concrete of the slab with the lip of the opening flush with its surface to facilitate the cleansing of the slab with water.
CPC § 105.0 Medium relevance — show source text
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. 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.
CPC § 502.6 Medium relevance — show source text
E 502.6 Outlets. Water outlets shall be convenient to access and, where not piped to individual recreational vehicle sites, shall not exceed 300 feet (91 m) from a site. Provisions shall be made to prevent accumulation of standing water or the creation of muddy conditions at each water outlet. E 502.7 Storage Tanks. Water storage tanks shall be constructed of impervious materials, protected against contamination, and provided with locked, watertight covers. Overflow or ventilation openings shall be down-facing and provided with a corrosion-resistant screening of not less than number 24 mesh to prevent the entrance of insects and vermin. Water storage tanks shall not have direct connections to sewers.

E 503.0 Recreational Vehicle Park Water Connec- tions for Individual Recreational Vehicles.

E 503.1 Location. Where provided, the water connections for potable water to individual recreational vehicle sites shall be located on the left rear half of the site (left side of recreational vehicle) within 4 feet (1219 mm) of the stand. E 503.2 Water Riser Pipe. Each potable water connection shall consist of a water riser pipe that is equipped with a threaded male spigot located not less than 12 inches (305 mm) but not more than 24 inches (610 mm) above grade level for the attachment of a standard water hose. The water riser pipe shall be protected from physical damage in accordance with this code. This connection shall be equipped with a listed antisiphon backflow prevention device.

E 504.0 Recreational Vehicle Park Drainage System. E 504.1 Where Required. An approved drainage system shall be provided in recreational vehicle parks for conveying and disposing of sewage. Where available, parks shall be connected to a public sewer system. E 504.2 Location. Sewer lines shall be located to prevent damage from vehicular traffic. E 504.3 Materials. Pipe and fittings installed in the drainage system shall be of material listed, approved, and installed in accordance with this code.

E 504.4 Pipe Sizes. The minimum diameters of drainage laterals, branches, and mains serving recreational vehicle sites shall be in accordance with Table E 504.4.

TABLE E 504.4

PIPE SIZES

MAXIMUM NUMBER OF
RECREATIONAL VEHICLE
STANDS SERVED MINIMUM PIPE SIZES
(inches)

5 3

36 4

71 5

120 6

440 8

For SI units: 1 inch = 25 mm

E 504.5 Cleanouts. Cleanouts shall be provided in accordance with Chapter 7 of this code. E 504.6 Drainage Inlet. Where provided, the site drainage system inlet connections for individual recreational vehicles shall be located to prevent damage by the parking of recreational vehicles or automobiles and shall consist of a sewer riser extending vertically to grade. The minimum diameter of the sewer riser pipe shall be not less than 3 inches (80 mm) in diameter, and shall be provided with a 4 inch (100 mm) inlet or not less than a 3 inch (80 mm) female fitting. **E 504.6.1 Location.

MAXIMUM NUMBER OF RECREATIONAL VEHICLE STANDS SERVED	MINIMUM PIPE SIZES (inches)
5	3
36	4
71	5
120	6
440	8

MAXIMUM NUMBER OF RECREATIONAL VEHICLE STANDS SERVED	MINIMUM PIPE SIZES (inches)
5	3
36	4
71	5
120	6
440	8

Frequently asked questions

What is the minimum pipe size I can use for a station outlet drop?

The code requires a minimum of DN15 (NPS 1/2) for drops to individual station outlets/inlets per §1323.1.2.

Can I use DN8 tubing for station drops if the outlet rarely used?

No. DN8 runouts are permitted only for alarm panels and instrument tubing per §1323.1.3; station drops must be at least DN15 as required by §1323.1.2.

If my system has 20 outlets, do I automatically stay at minimum DN15?

Not necessarily. While DN15 is the minimum per §1323.1.1–.2, a full sizing calculation per §1323.1.5 (using Table 1305.2 flows, diversity from Table 1323.1.5(1), equivalent length and pressure‑drop tables) may show a larger pipe is required. file

Where do I find the allowable pressure loss to each outlet?

The allowable maximum system pressure loss values are in Table 1323.1.5(2) (example: Oxygen and Medical Air = 5 psi; Medical Vacuum = 4 inHg). The sizing procedure requires that total loss to each outlet not exceed those values.

My run is very long — can I just upsize the drop instead of recalculating?

Long runs and demands outside the table ranges must be sized by accepted engineering methods under §1323.1.6. Simply upsizing a drop without proper calculation may still fail to meet the allowable losses or other performance criteria.

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