California Greywater H3 Irrigation Permit Procedure

Why this matters

California Plumbing Code (CPC) Chapter 16, Part 1, classifies non-potable systems by complexity and intended use. A Tier 3 (H3) greywater system collects laundry, lavatory, shower, and bathtub waste and distributes it to subsurface or mulch-basin irrigation. Cities and counties enforce CPC 16 plus their own local additions, and unpermitted greywater work is the highest-frequency code violation on residential additions in coastal California counties as of 2024. Installing without the permit blocks the certificate of occupancy and triggers retroactive permit fees plus correction work.

Tier classifications under CPC 16

CPC 1602 defines four non-potable system tiers:

• Single fixture clothes washer (laundry-to-landscape): no permit required when meeting CPC 1603.1.1 (12 conditions including no pump, subsurface or mulch only, no spray)
• Tier 1 (simple): single source, gravity flow, 250 gallons per day maximum
• Tier 2 (complex): multiple sources or pumped distribution, 250 gallons per day max, requires permit
• Tier 3 (H3): above 250 gallons per day, multiple sources, may include subsurface drip with filtration, requires permit and engineering when above 1,000 gpd

This SOP covers Tier 3 H3 (the most common permitted greywater installation in residential applications above 250 gpd).

Permit triggers and exemptions

Permit required when any of the following:

• System exceeds 250 gallons per day average daily flow
• Pump-driven distribution at any flow rate
• Surge tank or treatment component installed
• Drip irrigation with filtration installed regardless of source
• Multiple greywater sources combined upstream of distribution

No permit (Laundry to Landscape only) when ALL of CPC 1603.1.1 conditions met:

1. Greywater from clothes washer only
2. No pump beyond the integral washing machine pump
3. No surge or storage tank
4. Subsurface or mulch basin only, no spray
5. No connection to potable water supply
6. Vacuum breaker on three-way diverter valve
7. Conditions 7 through 12 covering signage, system labeling, irrigation cover, slope, and minimum distances

If any condition fails, the system becomes Tier 1 or Tier 2 and requires a permit.

Required setbacks

CPC Table 1603.2 sets minimum horizontal distances for any greywater irrigation field:

• Property line: 5 feet
• Building or structure: 2 feet
• Septic tank: 5 feet
• Septic leach field or seepage pit: 5 feet
• Water supply well: 100 feet (50 feet with engineered system, may be reduced further by local AHJ with hydrogeological analysis)
• Public water main: 10 feet
• Domestic water service line: 5 feet
• Pressure public sewer: 5 feet
• Pool or fountain: 10 feet
• Top of slope: 10 feet for slopes over 1V:5H

Subsurface drip lines must be a minimum of 2 inches below grade and covered by mulch or topsoil per CPC 1603.4.

Permit submittal package for H3

Submit to the local building department with the plumbing or grading permit:

1. Site plan (1/8 inch = 1 foot or 1/4 inch scale acceptable in most jurisdictions) showing all setback distances to features in Table 1603.2
2. Soils evaluation: percolation test results, soil type, depth to groundwater, depth to bedrock or impermeable layer
3. Plumbing diagram showing greywater sources, three-way diverter, surge tank if any, pump and pump controls, filtration if drip, and distribution field
4. Calculation of design daily flow per CPC 1603.4.2 (uses fixture unit method with greywater conversion factors)
5. Distribution field design: pipe diameter, hole spacing, number of laterals, distribution box detail
6. Manufacturer cut sheets for surge tank, pump, filter
7. Subsurface drip line submittal showing pressure compensation and root intrusion protection

Common reasons for permit rejection

• Spray irrigation in plan (CPC prohibits any greywater spray under any tier)
• Treated greywater piped to a hose bibb (CPC 1603.7 prohibits)
• Storage tank without a 24 hour drainage feature; tanks must drain or treat within 24 hours (CPC 1603.5)
• Combined blackwater and greywater into the same surge tank (this is sewage, not greywater)
• Distribution field within the dripline of a fruit tree where the fruit contacts soil (CPC 1603.4 prohibits irrigation that contacts edible food)
• Missing signage at the diverter valve labeled "Caution: Non-Potable Water" per CPC 1603.6

Inspection sequence

Most California AHJs inspect H3 greywater in three stages:

1. Rough inspection: surge tank and diverter installed, pipes in place but not buried
2. Distribution field open trench: subsurface drip or mulch basin construction visible before backfill
3. Final inspection: system operated through one full cycle while inspector observes, signage installed, owner provided with operations manual per CPC 1603.6

Owner instruction manual must include: source fixtures, list of approved cleaning products, emergency overflow procedure, annual filter maintenance schedule, and the name and license number of the installer.

References

• California Plumbing Code 2022, Chapter 16, Part 1 (Non-Potable Water Reuse Systems)
• CPC Section 1602 Tier Classifications
• CPC Section 1603 Greywater Systems
• CPC Table 1603.2 Greywater System Setback Distances
• California Department of Water Resources, Greywater System Guidelines (Bulletin 166-1)