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Building Code Reference

Got a CPC 422.1 correction?

Minimum plumbing fixture count

For builders in California, Greater Seattle, the Las Vegas area, the Denver area and Kansas City · CrossBeam Permits

What this code requires, how to fix it, and how cities and counties review it

What this code requires

CPC 422.1 is the California Plumbing Code section that sets the minimum number of plumbing fixtures a building must provide based on its occupant load and use type. The calculation determines how many water closets, lavatories, drinking fountains, and service sinks are required before a permit can pass plan check. If your fixture schedule does not include an occupant load calculation tied to the required fixture count, or if the count comes in short, you will get flagged under CPC 422.1.

How to fix it

  1. Determine the occupant load for each occupancy zone

    Look up the occupant load factor for your building use type from the applicable code table. Divide the floor area of each occupancy zone (gross or net, as the table specifies) by its load factor to get the design occupant count for that zone. For example, an office area at 3,000 sq ft at 150 sq ft per occupant gives 20 occupants. A restaurant dining area at 1,200 sq ft at 15 sq ft per occupant gives 80 occupants. For mixed-use buildings, calculate each zone separately and do not combine them under a single occupancy factor. Show the calculation on the plans.

  2. Split occupant count by gender for water closet calculation

    CPC 422.1 calculates water closet requirements separately for male and female occupants. The default split is 50 percent male and 50 percent female unless submitted information shows a different distribution. Take each zone total occupant count, divide in half, and apply the gender-specific water closet ratios from CPC Table 422.1. Note that urinals may substitute for a portion of male water closets in certain occupancies, but only if the urinals appear on the fixture schedule with the substitution math documented alongside.

  3. Apply CPC Table 422.1 minimum ratios for all fixture types

    CPC Table 422.1 specifies the minimum fixture count per type based on occupancy classification and occupant population. Read across the row for your occupancy, find the ratio (for example, 1 water closet per X occupants), and divide your occupant count by that ratio. Always round fractions up to the next whole number; for multiple occupancies, sum the fractions first and then round up (CPC 422.1.1). Apply this process to every fixture type: water closets, lavatories, drinking fountains (unless your occupancy qualifies for an exemption), and service sinks for janitorial use. Having extra of one type does not offset a shortfall in another.

  4. Build a fixture count table directly on the plumbing sheets

    Put the math on the plans, not just the fixture list. The fixture count table should include: occupancy type, gross floor area, occupant load factor, calculated occupant count, male/female split, minimum required per fixture type from Table 422.1, and count provided. A tabular format on sheet P1 or P0 with one row per occupancy zone and summed totals works well. For mixed-use buildings, break out each zone in its own row. The plan-checker needs to trace your arithmetic without making assumptions about what you intended.

  5. Confirm every fixture type independently meets or exceeds the minimum

    Walk the fixture table row by row: water closets provided vs. required, lavatories provided vs. required, and so on for every type. Every category must independently meet or exceed the minimum. Adding an extra toilet does not make up for a missing lavatory. If any row comes up short, add the fixture to the floor plan before resubmitting. Use fixture tags on the floor plan that match the fixture schedule so the checker can cross-reference a specific room without hunting through the plans.

  6. Calculate ADU and accessory dwelling units as separate entities

    If the project includes an ADU, junior ADU, or detached accessory structure with plumbing, calculate that unit fixture count independently. An ADU is a separate dwelling unit, not an extension of the primary house. For a studio or 1-bedroom ADU, the typical minimums are 1 water closet, 1 lavatory, 1 kitchen sink, and 1 bathing fixture. Table 422.1 also lists an automatic clothes washer connection for one- and two-family dwellings, so confirm with your jurisdiction whether the ADU needs its own. Show the ADU fixture schedule separately from the primary dwelling schedule. This applies even when both units share a single permit.

  7. Attach a concise response note when resubmitting

    When you resubmit after a CPC 422.1 correction, include a short response letter that calls out the sheet and schedule where the fix appears. Something direct: "CPC 422.1 addressed. See Sheet P1.1, Fixture Count Schedule, for updated occupant load basis and revised fixture totals." Plan-checkers reviewing a resubmittal are working through a stack of projects. A direct pointer to the fix saves them time and reduces the risk of a second correction round on the same item just because the revision was hard to find.

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Why you got flagged

Plan-checkers flag CPC 422.1 when the fixture schedule on the plumbing sheets does not match the calculated occupant load. The most common case: you have specified the fixtures your client wants but did not show the math proving you hit the minimum. A 2,000-square-foot office addition might need 1 water closet for the first 15 females and 1 for the first 50 males, plus lavatories at 1 for the first 50 females and 75 males — but if the plans just list "2 toilets, 2 sinks" with no occupant load basis, the checker cannot verify compliance and the correction is automatic.

The second scenario comes up on occupancy changes, which Table 422.1 covers whenever the change increases the occupant load. If you are converting a retail space into a restaurant, the occupant load factor changes dramatically — the fixture count follows, and plans that carry over the retail fixture count without recalculating for the new use fail every time.

Mixed-use buildings are another consistent source of corrections. Each occupancy type (office, retail, assembly) carries a different occupant load factor, and the fixture calculation must be broken out by use. Lumping the whole floor area under one occupancy type understates the required fixture count for the denser zones.

ADU additions also trip this section when the ADU plumbing is treated as part of the primary dwelling instead of as a separate dwelling unit. Each unit needs its own fixture count verified against the Table 422.1 minimum for a dwelling.

The official code

2025 California Plumbing Code (CPC) Section 422.1 and Table 422.1, Minimum Plumbing Facilities, California Building Standards Commission

Read the source →

Common questions

Does CPC 422.1 apply to residential ADUs or just commercial buildings?
CPC 422.1 applies to both. Residential projects, including ADUs, are subject to the minimum fixture count requirements. For an ADU, the minimums treat the unit as a separate dwelling: typically 1 water closet, 1 lavatory, and bathing facilities. The ADU fixture count is calculated independently from the main dwelling and documented separately on the plumbing plans. If your project is a residential remodel without an ADU, existing fixtures in unchanged portions may satisfy the count, but any new dwelling unit requires its own fixture count shown on the plans.
What is the difference between the CBC occupant load calculation and the CPC 422.1 fixture count?
The CBC occupant load tells you how many people the building is designed to hold, based on use type and floor area. CPC 422.1 uses that occupant count as an input to the minimum fixture calculation. So the CBC gives you the headcount; CPC Table 422.1 converts that headcount into a required number of water closets, lavatories, and other fixtures. Both documents need to appear on the plans and use consistent occupant counts. A common plan-check catch: the cover sheet shows one occupant load calculation and the plumbing fixture schedule implies a different one, which flags both codes at once.
Can urinals substitute for water closets to satisfy the CPC 422.1 minimum?
Yes, with limits. CPC 422.1 allows urinals to substitute for male water closets in certain occupancies, but the water closets cannot drop below two-thirds of the minimum, so urinals replace at most one-third. The remaining required water closets must still be provided. All urinals must appear on the fixture schedule with the substitution math shown. If you claim the substitution but do not document the calculation, the plan-checker will count only the water closets and may flag a deficiency even if the combination actually meets the minimum.
If we are converting a space to a new occupancy, do we recalculate CPC 422.1 from scratch?
Yes, when the change increases the occupant load, which is when Table 422.1 applies to an existing building. The occupant load factor changes with the use type, which changes the fixture minimum. A retail-to-restaurant conversion is the classic case: retail allows 60 gross sq ft per occupant while restaurant dining allows 15 net, so the calculated headcount is much higher for the same square footage, and the fixture count jumps accordingly. Even if the physical space is unchanged, the change-of-use permit must include an updated fixture schedule based on the new occupancy and its applicable ratios from CPC Table 422.1.
Are drinking fountains always required under CPC 422.1?
Not always. CPC Table 422.1 requires drinking fountains for most commercial and assembly occupancies but exempts single-family residential and individual dwelling units. For business occupancies, the table requires 1 drinking fountain per 150 occupants, and none are required for an occupant load of 30 or less. Where food is consumed indoors, water stations may substitute. If you are omitting drinking fountains on a commercial project, confirm the specific exemption applies to your occupancy type and note the basis on the fixture schedule so the plan-checker does not flag the omission as a deficiency.
Do the fixtures I add to meet the CPC 422.1 count also have to be accessible?
CPC 422.1 sets how many fixtures, not how accessible they are. Table 422.1 says that for requirements for persons with disabilities, Chapter 11A or 11B of the California Building Code shall be used. On a commercial project under CBC 11B-213.2, where toilet rooms are provided, each toilet room must comply with CBC 11B-603, and where lavatories are provided, at least 10 percent but no fewer than one must comply with CBC 11B-606 (CBC 11B-213.3.4). Show both on the plans: the fixture count table for CPC 422.1, and the accessible toilet room plans and details for CBC 11B.
My plans already show the right fixture count so why did I get a CPC 422.1 correction?
The most common reason is that the count is there but the calculation is not. A plan-checker who sees "3 water closets" on the fixture schedule cannot approve without verifying that 3 is actually the code minimum for your occupant load. They need to see the occupant load number, the applicable ratio from CPC Table 422.1, and the arithmetic that produces the required count. If the schedule just lists fixtures without a calculation basis, the correction is procedural, not substantive. The fix is adding a fixture count calculation table to the plans, not necessarily changing the number of fixtures you have already specified.

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