CPC · California Plumbing Code

What standards and installation rules apply to drinking water treatment units and softeners?

Q: Can the RO drain be tied to the dishwasher/drain arm?

No. The RO reject/drain must discharge through an air gap or an approved listed air‑gap device — it cannot be tied directly into dishwasher or other fixture drainage without the required air gap per § 611.2 .

Q: My softener is residential but installed in a small commercial tenant space — which standard applies?

Use Table 611.1 to determine the correct referenced standard for the application. Commercial point‑of‑entry treatment often requires ASSE 1087 and/or the commercial footnote in Table 611.1; verify the unit’s listing for commercial use. § 611.1

Q: Does connection tubing have to be copper?

No. The CPC requires connection tubing be the size and material recommended by the manufacturer — follow the manufacturer’s instructions and listed materials per § 611.3 .

For homeowners: the California Plumbing Code requires drinking‑water treatment devices be listed to the correct NSF/ASSE standard, have their waste drain through an air gap or a listed air‑gap device, be connected with manufacturer‑recommended tubing, have residential softeners sized per Table 611.4, and have their pressure losses included in the water‑system design so fixtures still get enough water pressure.

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Last reviewed: July 6, 2026

What the code requires — 2‑4 sentences

Drinking water treatment units must be listed to the referenced standards identified in § 611.1 and sized/installed per the CPC rules in § 611.0 – § 611.4. Discharge from those units must go to the drainage system through an air gap or an approved air‑gap device per § 611.2. Installers and designers also must include the pressure loss across treatment devices when sizing the water supply system per § 610.2.

The most important rule: discharge from a drinking‑water treatment unit must not connect directly to drainage or waste piping without an approved air gap — the unit’s drain must enter the drainage system through an air gap or listed air‑gap device. § 611.2

Requirements in detail

1) Which product standards apply

The CPC requires specific standards for different types of drinking water treatment units — the code’s Table 611.1 lists the required standard by application (point‑of‑use, point‑of‑entry, commercial). Examples (decision‑relevant):

Treatment application/type	Point‑of‑Use standard	Point‑of‑Entry standard	Commercial reference	Code Reference
Aesthetic contaminant reduction (filters)	NSF/ANSI 42	NSF/ANSI 42	ASSE 1087 and NSF/ANSI 42*	§ 611.1
Health‑related contaminant reduction (filters)	NSF/ANSI 53	NSF/ANSI 53	ASSE 1087 and NSF/ANSI 53*	§ 611.1
Water softener (residential POE)	–	NSF/ANSI 44	ASSE 1087	§ 611.1
Reverse osmosis	NSF/ANSI 58	NSF/ANSI/CAN 61	ASSE 1087	§ 611.1

Table footnote: some ASSE/ASSE+NSF requirements apply to commercial modular systems only — see Table 611.1 for those specifics. § 611.1

2) Drainage / discharge requirement (air gap)

Discharge from drinking water treatment units must enter the drainage system through an air gap sized per the air‑gap rules (Table 603.3.1) or by an air‑gap device that is listed to the referenced device standards (Table 603.2, NSF/ANSI 58, or IAPMO PS‑65). § 611.2
In plain terms: you may not run the waste from an RO or softener back into a drain connection without either the required measured air gap or an approved listed air‑gap assembly. § 611.2

3) Connection tubing

The tubing to and from drinking water treatment units must be of a size and material recommended by the manufacturer (don’t substitute undersized tubing). § 611.3

4) Sizing residential water softeners

Residential softener connection size is set by Table 611.4: 3/4‑inch connection for up to 22 bathroom groups served; 1‑inch for up to 43 bathroom groups served. Over four bathroom groups the softener size must be engineered for the installation. § 611.4

Required softener connection (in)	Number of bathroom groups served	Code Reference
3/4"	Up to 22	§ 611.4
1"	Up to 43	§ 611.4

5) Include device pressure loss in design

Pressure losses through water‑treating equipment (filters, softeners, RO units), meters, valves and fittings must be included in the hydraulic calculations — compute those losses in accordance with § 610.2 and related sizing rules in Chapter 6. The code also prohibits installing devices that produce an excessive pressure drop that prevents adequate supply to fixtures; absent manufacturer data, the device inlet/outlet diameter must be at least the diameter of the distribution piping it serves. § 610.2

Exceptions & special cases

The Table 611.1 footnote limits some ASSE/NSF requirements to commercial modular systems; check the table footnotes when applying commercial rules. § 611.1
Where manufacturers supply no pressure‑loss data, the CPC requires the device inlet/outlet (or connecting piping) not be smaller than the distribution piping to the fixtures served (to avoid excessive pressure drop). § 610.2
Appendix guidance and limitations: Appendix L contains additional listing/performance requirements and limits (for example, L 410.2 restricts discharge from softeners in low‑hardness water situations), so check appendices when relevant — Appendix L is informational but can contain local AHJ requirements.

Common mistakes

Omitting an air gap or using a non‑listed device for the unit discharge (violates § 611.2).
Installing a device listed to the wrong standard for its application (e.g., using a POE softener not listed to NSF/ANSI 44 for point‑of‑entry residential use) — check Table 611.1.
Forgetting to include the device pressure loss in the hydraulic sizing (leads to low system pressure at fixtures) — compute per § 610.2.
Using undersized connection tubing or fittings (tubing must match manufacturer recommendations) — § 611.3.
Installing softeners that discharge large regeneration wastes where local rules or Appendix L limit such discharge (check L 410.2 for limitations on residential discharge when hardness is ≤ 8 grains per gallon).

Worked example — residential RO + softener (numbers)

Scenario: A single‑family house will receive a point‑of‑entry water softener serving the whole house and a point‑of‑use reverse‑osmosis (RO) unit under the kitchen sink.

Standards:
- POE softener must be listed to NSF/ANSI 44 (softener) per § 611.1.
- The under‑sink RO must be listed to NSF/ANSI 58 per Table 611.1. § 611.1
Discharge (air gap):
- The RO drain (reject flow) must enter the drainage system through an air gap or a listed air‑gap device complying with the referenced tables/standards per § 611.2. You cannot hard‑pipe the RO waste directly into trap arm without the air gap.
Softener connection sizing:
- Designer counts plumbing demand and finds the softener serves 3 bathroom groups. Table 611.4 shows even 3/4‑inch service covers far more than 3 groups (up to 22 groups), so a 3/4‑inch connection would meet the specific table sizing. § 611.4
Pressure loss / hydraulic check:
- Available static pressure at the meter = 60 psi. Required minimum at highest fixture = 20 psi. Allowable system losses = 40 psi. Manufacturer pressure‑loss data: softener at peak flow = 6 psi, RO feed components = 4 psi. Remaining head for piping and fittings = 40 − 6 − 4 = 30 psi. Since the CPC requires including device losses in the sizing, these device losses must be included when selecting branch sizes and checking velocities per § 610.2. If losses left too small, increase pipe sizes or consult AHJ.

(Notes: the numeric pressures above are an example of how to apply the requirement — the CPC does not specify those numeric values in the section text; the code requires that such device losses be accounted for in the design per § 610.2.)

Related provisions (quick list)

§ 611.0 — Drinking Water Treatment Units (general scope).
§ 611.1 — Application; Table 611.1 referenced standards.
§ 611.2 — Air‑gap discharge requirement (drainage).
§ 611.3 — Connection tubing (manufacturer‑recommended size/material).
§ 611.4 — Sizing of residential water softeners; Table 611.4.
§ 610.2 — Pressure loss and requirement to include device losses in hydraulic design.
Table references for air gaps: Table 603.3.1 and Table 603.2 (air gap sizing / listed devices) — see § 611.2 for linkage.
Appendix L (L 410.x) — additional listing/efficiency and discharge limits for softeners and treatment devices (informational/appendix guidance).

Code references

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

CPC § 611.0 High relevance — show source text

611.0 Drinking Water Treatment Units. 611.1 Application. Drinking water treatment units shall comply with the applicable referenced standards in Table 611.1.

611.1.1 Alkaline Water Treatment. Alkaline water treatment devices shall comply with IAPMO IGC 322.

611.1.2 Scale Reduction Devices. Scale reduction devices shall comply with IAPMO/ANSI Z601. 611.2 Air Gap Discharge. Discharge from drinking water treatment units shall enter the drainage system through an air gap in accordance with Table 603.3.1 or an air gap device that complies with Table 603.2, NSF/ANSI 58, or IAPMO PS 65.

611.3 Connection Tubing. The tubing to and from drinking water treatment units shall be of a size and material as recommended by the manufacturer. 611.4 Sizing of Residential Softeners. Residential-use water softeners shall be sized in accordance with Table 611.4.

612.0 Residential Fire Sprinkler Systems. 612.1 Installation. Residential Sprinkler Systems shall be installed in compliance with the California Residential Code or the California Fire Code.

160 2025 CALIFORNIA PLUMBING CODE

WATER SUPPLY AND DISTRIBUTION

Col1	TABLE 611.1 DRINKING WATER TREATMENT UNITS	Col3	Col4
APPLICATION	RESIDENTIAL	RESIDENTIAL	COMMERCIAL
APPLICATION	POINT OF USE	POINT OF ENTRY	POINT OF ENTRY
Aesthetic Contaminant Reduction (filters)	NSF/ANSI 42	NSF/ANSI 42	ASSE 1087 and NSF/ANSI 42*
Health Related Contaminant Reduction (filters)	NSF/ANSI 53	NSF/ANSI 53	ASSE 1087 and NSF/ANSI 53*
Water Softener	–	NSF/ANSI 44	ASSE 1087
Ultraviolet Water Treatment	NSF/ANSI 55	NSF/ANSI 55	ASSE 1087
Reverse Osmosis	NSF/ANSI 58	NSF/ANSI/CAN 61	ASSE 1087
Distillation	NSF/ANSI 62	NSF/ANSI 62	ASSE 1087

 - Required for commercial modular systems only.

TABLE 611.4 SIZING OF RESIDENTIAL WATER SOFTENERS [4]

REQUIRED SIZE OF SOFTENER CONNECTION (inches)	NUMBER OF BATHROOM GROUPS SERVED1
3⁄4	up to 22
1	up to 43

For SI units: 1 inch = 25 mm

CPC § 610.10 High relevance — show source text
LAV LAV UR UR WC WC

EXAMPLE 610.10

SIZING METHOD FOR PUBLIC USE FIXTURES

USING TABLE 610.10

610.11 Sizing Systems for Flushometer Tanks. The size of branches and mains serving flushometer tanks shall be consistent with the sizing procedures for flush tank water closets. 610.12 Sizing for Velocity. Water piping systems shall not exceed the maximum velocities listed in this section or Appendix A.

610.12.1 Copper Tube Systems. Maximum velocities in copper and copper alloy tube and fitting systems shall not exceed 8 feet per second (ft/s) (2.4 m/s) in cold water and 5 ft/s (1.5 m/s) in hot water. 610.12.2 Tubing Systems Using Copper Fittings. Maximum velocities through copper fittings in tubing other than copper shall not exceed 8 ft/s (2.4 m/s) in cold water and 5 ft/s (1.5 m/s) in hot water. 610.13 Exceptions. The provisions of this section relative to the size of water piping shall not apply to the following:

(1) Water supply piping systems designed in accordance with recognized engineering procedures acceptable to the Authority Having Jurisdiction.

(2) Alteration of or minor additions to existing installations provided the Authority Having Jurisdiction finds that there will be an adequate supply of water to operate fixtures.

(3) Replacement of existing fixtures or appliances.

(4) Piping that is part of fixture equipment.

(5) Unusual conditions where, in the judgment of the Authority Having Jurisdiction, an adequate supply of water is provided to operate fixtures and equipment.

(6) The size and material of irrigation water piping installed outside of a building or structure and separated from the potable water supply by means of an approved air gap or backflow prevention device are not regulated by this code. The potable water piping system supplying each such irrigation system shall be adequately sized as required elsewhere in this chapter to deliver the full connected demand of both the domestic use and the irrigation systems.

611.0 Drinking Water Treatment Units. 611.1 Application. Drinking water treatment units shall comply with the applicable referenced standards in Table 611.1.

611.1.1 Alkaline Water Treatment. Alkaline water treatment devices shall comply with IAPMO IGC 322.

611.1.2 Scale Reduction Devices. Scale reduction devices shall comply with IAPMO/ANSI Z601. 611.2 Air Gap Discharge. Discharge from drinking water treatment units shall enter the drainage system through an air gap in accordance with Table 603.3.1 or an air gap device that complies with Table 603.2, NSF/ANSI 58, or IAPMO PS 65.

611.3 Connection Tubing. The tubing to and from drinking water treatment units shall be of a size and material as recommended by the manufacturer. 611.4 Sizing of Residential Softeners. Residential-use water softeners shall be sized in accordance with Table 611.4.

612.0 Residential Fire Sprinkler Systems. 612.1 Installation. Residential Sprinkler Systems shall be installed in compliance with the California Residential Code or the California Fire Code.

160 2025 CALIFORNIA PLUMBING CODE

), Copyright © 2025 IAPMO, and may not be used for any other purpose or distributed to any other persons or parties.
CPC § 408.1.1 High relevance — show source text
APPENDIX L

L 408.1.1 Condensate Drainage Recovery. Condensate from air-conditioning, boiler and steam systems used to supply water for non-potable water systems shall be in accordance with Section 1506.0.

L 409.0 Water-Powered Sump Pumps. L 409.1 General. Sump pumps powered by potable or reclaimed (recycled) water pressure shall be used as an emergency backup pump and shall comply with IAPMO PS 119. The water-powered pump shall be equipped with a battery powered alarm having a minimum rating of 85 dBa at 10 feet (3048 mm). Water-powered pumps shall have a water efficiency factor of pumping at least 1.4 gallons (5.3 L) of water to a height of 10 feet (3048 mm) for every gallon of water used to operate the pump, measured at a water pressure of 60 psi (414 kPa). Pumps shall be labeled as to the gallons of water pumped per gallon of potable water consumed.

Water-powered stormwater sump pumps shall be equipped with a reduced pressure principle backflow prevention assembly.

L 410.0 Water Softeners and Treatment Devices.

L 410.1 Water Softeners. Water softeners shall be listed to

NSF/ANSI 44. Water softeners shall have a rated salt efficiency exceeding 3400 grains (gr) (0.222 kg) of total hardness exchange per pound (0.5 kg) of salt, based on sodium chloride (NaCl) equivalency, and shall not generate more than 4 gallons (15.1 L) of water per 1000 grains (0.0647 kg) of hardness removed during the service cycle.

L 410.2 Water Softener Limitations. In residential buildings, where the supplied potable water hardness is equal to or less than 8 grains per gallon (gr/gal) (137 mg/L) measured as total calcium carbonate equivalents, water softening equipment that discharges water into the wastewater system during the service cycle shall not be allowed, except as required for medical purposes.

L 410.3 Point-of-Use Reverse Osmosis Water Treat- ment Systems. Reverse osmosis water treatment systems shall be equipped with automatic shutoff valves to prevent discharge when there is no call for producing treated water. Reverse osmosis water treatment systems shall comply with NSF/ANSI 58 and ASSE 1086.

L 410.4 Drinking Water Treatment Systems. Drinking water treatment systems shall be listed to WQA/ASPE/ANSI S-803.

L 411.0 Landscape Irrigation Systems. L 411.1 General. Where landscape irrigation systems are installed, they shall be in accordance with Section L 411.1.1 through Section L 411.17. L 411.1.1 Irrigation Design and Installation. The Authority Having Jurisdiction shall have the authority to require landscape irrigation contractors, installers, or designers to demonstrate competency. The system shall be designed and record drawings showing changes during installation shall be made available for the owner and for any required inspections. Where required by the Authority
CPC § 611.3 High relevance — show source text
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

701.0 General . . . . . . . . . . . . . . . . . . . . .165

701.1 Applicability . . . . . . . . . . . . . . . . . .165

701.2 Drainage Piping . . . . . . . . . . . . . .165

701.3 Drainage Fittings . . . . . . . . . . . . .165

701.4 Continuous Wastes . . . . . . . . . . .165

701.5 Lead . . . . . . . . . . . . . . . . . . . . . . .165

701.6 Caulking Ferrules . . . . . . . . . . . . .165

701.7 Soldering Bushings . . . . . . . . . . . .165

Table 701.6 Caulking Ferrules . . . . . . . . . . . . .165

Table 701.7 Soldering Bushings . . . . . . . . . . . .165

702.0 Fixture Unit Equivalents . . . . . . . .165

702.1 Trap Size . . . . . . . . . . . . . . . . . . .165

Table 701.2 Materials for Drain, Waste, Vent Pipe and Fittings . . . . . . . . .166

Table 702.1 Drainage Fixture Unit Values (DFU) . . . . . . . . . . . . . . . .167

Table 702.1(1) Maximum Drainage Fixture Units for a Trap and Trap Arm . . .168

702.2 Intermittent Flow . . . . . . . . . . . . . .168

CPC § 611.1 High relevance — show source text

WATER SUPPLY AND DISTRIBUTION

Col1	TABLE 611.1 DRINKING WATER TREATMENT UNITS	Col3	Col4
APPLICATION	RESIDENTIAL	RESIDENTIAL	COMMERCIAL
APPLICATION	POINT OF USE	POINT OF ENTRY	POINT OF ENTRY
Aesthetic Contaminant Reduction (filters)	NSF/ANSI 42	NSF/ANSI 42	ASSE 1087 and NSF/ANSI 42*
Health Related Contaminant Reduction (filters)	NSF/ANSI 53	NSF/ANSI 53	ASSE 1087 and NSF/ANSI 53*
Water Softener	–	NSF/ANSI 44	ASSE 1087
Ultraviolet Water Treatment	NSF/ANSI 55	NSF/ANSI 55	ASSE 1087
Reverse Osmosis	NSF/ANSI 58	NSF/ANSI/CAN 61	ASSE 1087
Distillation	NSF/ANSI 62	NSF/ANSI 62	ASSE 1087

 - Required for commercial modular systems only.

TABLE 611.4 SIZING OF RESIDENTIAL WATER SOFTENERS [4]

REQUIRED SIZE OF SOFTENER CONNECTION (inches)	NUMBER OF BATHROOM GROUPS SERVED1
3⁄4	up to 22
1	up to 43

For SI units: 1 inch = 25 mm

Notes: 1 Installation of a kitchen sink and dishwasher, laundry sink, and automatic clothes washer permitted without additional size increase. 2 An additional water closet and lavatory permitted. 3 Over four bathroom groups, the softener size shall be engineered for the specific installation. 4 See also Appendix A, Recommended Rules for Sizing the Water Supply System, and Appendix C, Alternate Plumbing Systems, for alternate methods of sizing water supply systems.

613.0 Domestic Hot-Water Distribution Systems for Health Facilities and Clinics. [OSHPD 1, 2, 3, 4 & 5]

613.1 The domestic water-heating equipment and distribu- tion systems shall supply water at the temperature and amounts shown in Table 613.1. Where the system is designed by a mechanical engineer, appropriate diversity factors may be utilized.

TABLE 613.1

[OSHPD 1, 2, 3, 4 & 5] HOT WATER USE

Col1	CLINICAL	DIETARY1	LAUNDRY2
Liter/Hour/Bed	11.9	7.2	7.6
Gallons/Hour/Bed	3	2	2
Temperature °C	41-49.0	49.03	71.0
Temperature °F	105-120.0	120.03	160.0

1 Rinse water temperature at warewasher or potsinks shall be 180°F (82°C) unless a chemical disinfection is provided.

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 § 14.1 High relevance — show source text
14.1| |NFPA 99-2024|Health Care Facilities Code|Miscellaneous|1301.3, 1309.13(2),
1317.1(9), 1324.5.9.4,
1326.3, 1326.4(3),
1326.8(4), 1327.1| |NFPA 211-2024|Standard for Chimneys, Fireplaces, Vents, and Solid Fuel-
Burning Appliances|Fuel Gas,
Appliances|509.5.2, 509.5.3,
509.5.6.1, 509.5.6.3| |NFPA 409-2022|Standard on Aircraft Hangars|Miscellaneous|507.15| |NFPA 780-2023|Standard for the Installation of Lightning Protection Systems|Fuel Gas|1211.5| |NFPA 1192-2021|Standard on Recreational Vehicles|Fuel Gas|1202.3(18)| |NSF|NSF|NSF|NSF| |NSF/ANSI 3-2021|Commercial Warewashing Equipment|Appliances|414.1| |NSF/ANSI 14-2020|Plastics Piping System Components and Related Materials|Miscellaneous|301.2.3, 604.1,
605.9.1, 606.1| |NSF/ANSI 42-2021|Drinking Water Treatment Units – Aesthetic Effects|Appliances|Table 611.1| |NSF/ANSI 44-2018|Residential Cation Exchange Water Softeners|Appliances|Table 611.1| |NSF/ANSI 53-2020|Drinking Water Treatment Units-Health Effects|Appliances|Table 611.1| |NSF/ANSI 55-2020|Ultraviolet Microbiological Water Treatment Systems|Appliances|Table 611.1| |NSF/ANSI 58-2020|Reverse Osmosis Drinking Water Treatment Systems|Appliances|Table 611.1, 611.2| |NSF/ANSI/CAN 61-2021|Drinking Water System Components – Health Effects|Miscellaneous|415.1, 417.1, 604.1,
604.9, 606.1, 607.3,
608.2, 609.8.2, Table
611.1| |NSF/ANSI 62-2021|Drinking Water Distillation Systems|Appliances|Table 611.1| |NSF/ANSI 184-2019|Residential Dishwashers|Appliances|414.1| |NSF/ANSI 350-2020|Onsite Residential and Commercial Water Reuse Treatment
Systems
Note: NSF/ANSI 350, amended sections follow:
5.6 Electrical Components. Electrical components.The
California Electrical Code shall be followed for all electrical
components, system installation, and system operation.|Miscellaneous|1501.7, 1506.8,
1506.10.2| |NSF/ANSI 359-2018|Valves for Crosslinked Polyethylene (PEX) Water Distribution
Tubing Systems|Valves|606.
CPC § 407.1 High relevance — show source text
1 do not apply, no additional dedicated meter is
required.| |Tenant Spaces - Non-residential, car
washes|All water supplies to individual non-residential tenant spaces for indoor water use where any of the
following conditions exist:
(1)
The nominal size of a water supply pipe(s) to the individual tenant space is greater than ½
inch, or
(2)
Water consumption within in the tenant space is estimated or expected to average greater than
1000 gallons/day (gal/d).
Where water is supplied to tenant space that is not required to have dedicated meter, the water sup-
ply pipe (s) shall be accessible to install a meter.
Exception: Where a water purveyor has individual meters for each tenant space and the other
meter requirements included in Table L 407.1 do not apply, no additional dedicated meter is
required.|

For SI units: 1 gallon per day = 3.785 L/day, 1 inch = 25.4 mm, 1 square foot = 0.0929 m [2], 1000 British thermal units per hour = 0.293 kW, 1 cubic foot per minute (CFM) = 0.4719 L/s, 1 ton = 3.5169 kW

504 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

L 408.1.1 Condensate Drainage Recovery. Condensate from air-conditioning, boiler and steam systems used to supply water for non-potable water systems shall be in accordance with Section 1506.0.

L 409.0 Water-Powered Sump Pumps. L 409.1 General. Sump pumps powered by potable or reclaimed (recycled) water pressure shall be used as an emergency backup pump and shall comply with IAPMO PS 119. The water-powered pump shall be equipped with a battery powered alarm having a minimum rating of 85 dBa at 10 feet (3048 mm). Water-powered pumps shall have a water efficiency factor of pumping at least 1.4 gallons (5.3 L) of water to a height of 10 feet (3048 mm) for every gallon of water used to operate the pump, measured at a water pressure of 60 psi (414 kPa). Pumps shall be labeled as to the gallons of water pumped per gallon of potable water consumed.

Water-powered stormwater sump pumps shall be equipped with a reduced pressure principle backflow prevention assembly.

L 410.0 Water Softeners and Treatment Devices.

L 410.1 Water Softeners. Water softeners shall be listed to

NSF/ANSI 44. Water softeners shall have a rated salt efficiency exceeding 3400 grains (gr) (0.222 kg) of total hardness exchange per pound (0.5 kg) of salt, based on sodium chloride (NaCl) equivalency, and shall not generate more than 4 gallons (15.1 L) of water per 1000 grains (0.0647 kg) of hardness removed during the service cycle.
CPC § 4.2.1 Medium relevance — show source text
1101.4.2.1, 1104.4.2.2

AIR GAPS

Backflow prevention . . . . . . 603.2, Table 603.2, 603.3.1, Table 603.3.1, 603.4.4

Definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 203.0

Discharge from drinking

water treatment units . . . . . . . . . . . . . . . . . . . . . 611.2

AIR TANK . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .710.11

ALTERATIONS AND REPAIRS

Fuel gas piping . . . . . . . . . . . .1203.1, 1213.1.2, 1213.4.2

Health care facilities . . . . . . . . . . . . . . . . . . . . . . .1301.5

Plumbing systems . . . . . . . . . . . . . . . . . .102.4, 301.2.5 ALTERNATE MATERIALS, DESIGN,

AND METHODS . . . . . . . . . . . . . . . . . . . . . . . . . . . .301.3

ALTERNATE WATER SOURCE

Definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .203.0

For nonpotable applications . . .Chapter 15, Chapter 16 For special water features . . . . . . . . . . . . . . . . .L 406.1

Future connections . . . . . . . . . . . . . . . . . . . . .1504.9.1

Identification of piping . . . . . . . . . . . . . . . . . . . . .601.3.3 Nonpotable rainwater catchment system . . . . . . . . . . .Table 1601.5, 1602.4

Potable rainwater

catchment system . . . . . . . . . . . . . . . . . . . . . .K 102.2 ANODELESS RISER, DEFINITION . . . . . . . . . . . . . . .203.0

APPLIANCES

Automatically operated . . . . . . . . . . . .509.3.4, 509.5.7.1 Categorized vent diameter/area, definition . . . . . . . . . . . . . . . . . .203.0 Connections to building fuel gas piping . . . . . . . . . . . . . . . . . . . . . . . . .1212.0

Definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .203.0

Direct-vent . . . . . . . . . . . . . . . .206.0, 509.2.6, 509.5.10.1,

509.8.1, 509.12

2025 CALIFORNIA PLUMBING CODE 563

CPC § 505.3 Medium relevance — show source text

2025 CALIFORNIA PLUMBING CODE 349

REFERENCED STANDARDS

TABLE 1701.1 (continued) REFERENCED STANDARDS

STANDARD NUMBER	STANDARD TITLE	APPLICATION	REFERENCED SECTION
NFPA 88A-2023	Parking Structures	Miscellaneous	507.14.1
NFPA 99-2024	Health Care Facilities Code	Miscellaneous	1301.3, 1309.13(2), 1317.1(9), 1324.5.9.4, 1326.3, 1326.4(3), 1326.8(4), 1327.1
NFPA 211-2024	Standard for Chimneys, Fireplaces, Vents, and Solid Fuel- Burning Appliances	Fuel Gas, Appliances	509.5.2, 509.5.3, 509.5.6.1, 509.5.6.3
NFPA 409-2022	Standard on Aircraft Hangars	Miscellaneous	507.15
NFPA 780-2023	Standard for the Installation of Lightning Protection Systems	Fuel Gas	1211.5
NFPA 1192-2021	Standard on Recreational Vehicles	Fuel Gas	1202.3(18)
NSF	NSF	NSF	NSF
NSF/ANSI 3-2021	Commercial Warewashing Equipment	Appliances	414.1
NSF/ANSI 14-2020	Plastics Piping System Components and Related Materials	Miscellaneous	301.2.3, 604.1, 605.9.1, 606.1
NSF/ANSI 42-2021	Drinking Water Treatment Units – Aesthetic Effects	Appliances	Table 611.1
NSF/ANSI 44-2018	Residential Cation Exchange Water Softeners	Appliances	Table 611.

CPC § 610.3 Medium 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 § 603.4.2 Medium relevance — show source text

2025 CALIFORNIA PLUMBING CODE 347

REFERENCED STANDARDS

TABLE 1701.1 (continued) REFERENCED STANDARDS

STANDARD NUMBER	STANDARD TITLE	APPLICATION	REFERENCED SECTION
ASSE/IAPMO/ANSI 6020- 2021	Medical Gas Systems Inspectors	Miscellaneous	1324.5.4.7, 1324.5.6.2, 1324.5.6.5
ASSE/IAPMO/ANSI 6030- 2021	Medical Gas Systems Verifiers	Miscellaneous	1324.5.4.7, 1324.5.6.2, 1324.5.6.5, 1324.5.7.2
ASSE/IAPMO/ANSI 6035- 2021	Bulk Medical Gas/Cryogenic Fluid Central Supply Systems Verifiers	Miscellaneous	1324.5.7.3
ASSE/IAPMO/ANSI Series 7000-2020	Residential Potable Water Fire Sprinkler System Installers & Inspectors for One- and Two-Family Dwellings	Miscellaneous	612.1
ASSE/IAPMO/ANSI 12010-2021	Environment of Care, Infection Control and Construction Risk Assessment Professional Qualification Standard	Professional Qualifications	1303.9
IAPMO IGC 78-2019	Drain, Waste and Vent (DWV) Internal Cleanout Fittings	DWV Components	Table 707.2
IAPMO IGC 109-2019	Water Distribution Manifolds	Valves	606.5.1
IAPMO IGC 127-2018	Combined Hand-Washing Systems	Fixtures	407.1, 420.1
IAPMO IGC 154-2019	Shower and Tub/Shower Enclosures, Bathtubs with Glass Pres- sure-Sealed Doors, and Shower/Steam Panels	Fixtures	408.1
IAPMO IGC 167-2011ae2 (R2021)	Solid Waste Containment Interceptors	Interceptors	Table 1009.1
IAPMO IGC 183-2016	Oil/Water Separators and Coalescing Plate Separators	DWV Components	Table 1009.1, 1017.2
IAPMO IGC 196-2018	Condensate Traps and Overflow Switches for Air-Conditioning Systems	Condensate Traps	814.4
IAPMO IGC 224-2018	ABS, PVC and Cast Iron DWV Test Fitting with Integral Cleanout	DWV Components	Table 707.2
IAPMO IGC 305-2019	ABS and PVC Horizontal Backwater Valves with Lifting Devices	Valves	710.6
IAPMO IGC 322-2018	Alkaline Water – Drinking Water Treatment Units	Miscellaneous	611.1.

Frequently asked questions

Can the RO drain be tied to the dishwasher/drain arm?

No. The RO reject/drain must discharge through an air gap or an approved listed air‑gap device — it cannot be tied directly into dishwasher or other fixture drainage without the required air gap per § 611.2.

What if the manufacturer gives no pressure‑loss data for a filter?

If no pressure‑loss data is provided, the CPC requires that the device inlet/outlet or connecting piping be not less than the diameter of the distribution piping to the fixtures served to avoid excessive pressure drop; and you must not install a device that produces an excessive pressure drop that prevents adequate service. See § 610.2.

My softener is residential but installed in a small commercial tenant space — which standard applies?

Use Table 611.1 to determine the correct referenced standard for the application. Commercial point‑of‑entry treatment often requires ASSE 1087 and/or the commercial footnote in Table 611.1; verify the unit’s listing for commercial use. § 611.1

Are there limits on softener discharge (regeneration brine) in residences?

Appendix L contains guidance and limits (for example, restrictions when supplied potable hardness ≤ 8 grains per gallon) — check local AHJ and Appendix L (L 410.2) for discharge restrictions.

Does connection tubing have to be copper?

No. The CPC requires connection tubing be the size and material recommended by the manufacturer — follow the manufacturer’s instructions and listed materials per § 611.3.

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How are residential fire sprinkler systems covered under water distribution rules?

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What are the rules for potable and nonpotable rainwater catchment systems and connections?

Water Treatment, Alternate Sources, and Special Systems

California Plumbing Code