Appendix S Onsite Stormwater Treatment Systems — 2025 California Plumbing Code

(Matrix Adoption Tables are non-regulatory, intended only as an aid to the code user. See Chapter 1 for state agency authority and building applications.)

This state agency does not adopt sections identified with the following symbol: The Office of the State Fire Marshal’s adoption of this chapter or individual sections is applicable to structures regulated by other state agencies pursuant to Section 1.11.0.

ONSITE STORMWATER TREATMENT SYSTEMS

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

The provisions of this appendix shall apply to the water quality, monitoring, design, construction, alteration, repair, and operation requirements of onsite stormwater treatment systems for nonpotable use.

Where approved or required by the Authority Having Jurisdiction, stormwater shall be permitted to be used in lieu of potable water for uses such as, but not limited to, water closets, urinals, clothes washers, ornamental plant irrigation, and dust suppression.

Onsite stormwater treatment systems shall meet the design, construction, and performance requirements of Section S 101.3.1 or Section S 101.3.2.

S 101.3.1 Listed Stormwater Treatment Systems. Onsite stormwater treatment systems shall be listed to ARCSA/ASPE 78, installed according to the manufacturer's instructions, and commissioned in accordance with Section S 101.13.

S 101.3.2 Alternative Design Systems. Where approved by the Authority Having Jurisdiction, onsite stormwater treatment systems for residential and commercial applications shall comply with the provisions of Sections S 101.4 through Section S 101.15.

It shall be unlawful for any person to construct, install, alter, or cause to be constructed, installed, or altered any stormwater treatment system in a building or on a premise without first obtaining a permit to do such work from the Authority Having Jurisdiction.

System components shall be properly identified as to the manufacturer.

Stormwater treatment systems shall be constructed of materials that are compatible with the type of pipe and fitting materials, water treatment, and water conditions in the system.

Stormwater treatment systems shall be designed to meet the log reduction targets as set forth in Table S 101.7. To meet the log reduction in Table S 101.7, treatment processes used in stormwater systems shall comply with Section S 101.8 for validation or be operated according to conditions approved by the Authority Having Jurisdiction.

Stormwater treatment systems shall be designed to meet the effluent water quality parameters for water closet and urinal fixture use listed in Table S 101.8.

Where required by the Authority Having Jurisdiction, treatment processes shall be tested to verify the pathogen reduction performance. The treatment processes shall be validated through third-party component validation or

field verification using challenge testing. The results of the third-party component validation and/or challenge testing shall be summarized in a validation report prepared by a registered design professional. The validation report shall document the treatment technology's log reduction performance, including information on the operating conditions and surrogate parameters.

TABLE S 101.7 LOG REDUCTION TARGETS FOR 10 [-4] INFECTIONS PER

PERSON PERYEAR BENCHMARKS FOR STORMWATER

TREATMENT SYSTEMS

Notes: 1 Non-food. 2 Stormwater can contain some quantity of fecal contamination. The extent of fecal contamination present will depend on site-specific conditions. The appropriate LRT to apply for a stormwater treatment system depend on the site-specific extent of likely contamination of stormwater with fecal contamination.

TABLE S 101.8

EFFLUENT WATER QUALITY PARAMETERS FOR WATER

CLOSET AND URINAL FIXTURE USE

Potable water systems shall be protected against nonpotable water in accordance with Section 602.0 and Section 603.0 of this code.

TABLE S 101.7 LOG REDUCTION TARGETS FOR 10 [-4] INFECTIONS PER

PERSON PERYEAR BENCHMARKS FOR STORMWATER

TREATMENT SYSTEMS

Notes: 1 Non-food. 2 Stormwater can contain some quantity of fecal contamination. The extent of fecal contamination present will depend on site-specific conditions. The appropriate LRT to apply for a stormwater treatment system depend on the site-specific extent of likely contamination of stormwater with fecal contamination.

TABLE S 101.8

EFFLUENT WATER QUALITY PARAMETERS FOR WATER

CLOSET AND URINAL FIXTURE USE

Monitoring of stormwater treatment systems shall be based on the risk level in accordance with Table S 101.11(1). The parameters listed in Table S 101.11(2) shall be monitored by sensors placed in the effluent of the system and connected to a smart controller. The smart controller shall activate an alarm when the parameters in Table S 101.11(2) are outside the specifications and shall shut the system down when the alarm is not acknowledged after a period of 8 hours has elapsed. For Category 2, quarterly grab samples shall be taken out of the effluent and analyzed by an accredited lab. The sensors' accuracy and response shall be validated upon commissioning of the system by an independent third party.

TABLE S 101.11(1)

RISK LEVELS

• See Section S 101.2 for other uses approved by the Authority Having Jurisdiction.

TABLE S 101.11(2)

MONITORING PARAMETERS

The design and installation of onsite stormwater treatment systems shall meet the requirements of Section S 101.12.1 through Section S 101.12.6.

S 101.12.1 Connections to Potable or Reclaimed (Recycled) Water Systems. Stormwater treatment systems shall have no direct connection to any potable water supply or reclaimed (recycled) water source system. Potable water or reclaimed (recycled) water shall be permitted to be used as makeup water for a stormwater treatment system provided the potable or reclaimed (recycled) water supply connection is protected by an airgap. S 101.12.2 Bypass Connection. A bypass shall be provided for the input connection to the stormwater treatment system. The bypass shall be a diverter valve normally open to the stormwater treatment system. The normally closed port of the diverter valve shall be connected directly to the storm drainage system or combined sewer system in accordance with this code.

TABLE S 101.11(1)

RISK LEVELS

• See Section S 101.2 for other uses approved by the Authority Having Jurisdiction.

S 101.12.3 Overflow Connection. Stormwater treatment overflow shall be connected directly to the storm drainage or combined sewer system in accordance with this code. The overflow shall be provided with a backwater valve at the point of connection to the storm drainage or combined sewer system. The backwater valve shall be accessible for inspection and maintenance.

S 101.12.4 Fail-Safe Mechanisms. Stormwater treatment systems shall be equipped with an automatic shutdown device of the treatment process in the event of a malfunction.

S 101.12.5 Flow Meter Totalizer. Buildings with stormwater treatment systems shall include a flow meter totalizer on the treated stormwater distribution system and a flow meter totalizer on the potable make-up water pipeline to the stormwater treatment system. S 101.12.6 Cross-Connection Inspection and Testing. A cross-connection test is required in accordance with Section 1502.0. Before the building is occupied or the system is activated, the installer shall perform the initial cross-connection test in the presence of the Authority Having Jurisdiction. The test shall be ruled successful by the Authority Having Jurisdiction before final approval is granted.

Onsite stormwater treatment systems shall be commissioned in accordance with the requirements of Section S 101.13.1 through Section S 101.13.4.

S 101.13.1 Commissioning Requirements. Commissioning for stormwater treatment systems shall be included in the design and construction processes of the project. Commissioning shall be performed by a person who demonstrates competency in commissioning stormwater treatment systems as required by the Authority Having Jurisdiction. S 101.13.2 Commissioning Plan. The construction documents shall include the commissioning plan for the stormwater treatment system. The commissioning plan shall be approved by the Authority Having Jurisdiction prior to commissioning the stormwater treatment system. The commissioning plan shall include the following:

(1) General project information.

(2) Equipment to be tested, including the test methodology.

(3) Processes to be tested.

(4) Criteria or process for testing.

(5) Criteria or process for acceptance.

(6) Commissioning team contact information.

(7) Commissioning process activities, schedules, and responsibilities.

(8) Plans for the completion of functional performance testing, post construction documentation and training, and the commissioning report. S 101.13.3 Performance Testing. Performance tests shall verify that the installation and operation of the

TABLE S 101.11(2)

MONITORING PARAMETERS

equipment of the stormwater treatment system is in accordance with the approved plans and specifications. The performance test report shall include the equipment tested, the testing methods utilized, and proof of proper calibration of the equipment. S 101.13.4 Commissioning Report. The commissioning report shall be submitted to the Authority Having Jurisdiction.

An operation and maintenance manual shall be provided in accordance with Section 1501.6 and shall also include the following:

(1) Instructions on operating and maintaining the system, including treatment process operations, instrumentation and alarms, and chemicals storage and handling.

(2) Site equipment inventory and maintenance notes.

(3) Equipment/system warranty documentation and information.

(4) As-built design drawings.

(5) Details on training requirements and qualifications of personnel responsible for operating the system.

(6) Maintenance schedule.

Field inspections shall take place during and after construction while the contractor is on-site to verify that the stormwater treatment system components have been properly supplied and installed according to the plans and specifications used for installation. Record drawings shall be maintained with changes to the approved plans by the contractor and available for periodic inspection as needed.

For the purpose of this appendix, the following definitions shall apply: Challenge Test. The evaluation of a unit treatment process for pathogen log 10 reduction performance using selected surrogate or indigenous constituents. This includes a detailed technology evaluation study conducted to challenge the treatment technology over a wide range of operational conditions. Commissioning. The activities associated with bringing a new process into normal working condition. Field Verification. Performance confirmation study conducted using challenge testing, including surrogate microorganisms and/or other non-biological surrogates, usually during startup and commissioning. Log 10 Reduction. The removal of a pathogen or surrogate in a unit process expressed in log 10 units of the effluent concentration over the influent concentration (e.g., a 1-log reduction equates to 90% removal, 2-log reduction to 99% removal, 3-log reduction to 99.9% removal, and so on). Log 10 Reduction Target (LRT). The log 10 reduction target for the specified pathogen group (e.g., viruses, bacteria, or protozoa) to achieve the identified level of risk to individuals (e.g., 10 [-4] infection per year). Stormwater. Natural precipitation that has contacted a surface at grade, below grade, or above ground parking surfaces.

Surrogate. A biological, chemical, or physical parameter used to verify pathogen reductions performances. Validation Report. Report documenting the results of a challenge test conducted during field verification.