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Trade Exam · Module 4

Shower and Tub Installation: Valves, Pans and Receptors

Lesson 8 of 9~20 minFree previewCurrent as of September 2026Leer en español

Showers and bathtubs under the 2025 California Plumbing Code: pressure balance or thermostatic valves that hold a showerhead to 120 F, showerheads at 1.8 gpm at 80 psi, 2 inch shower and 1-1/2 inch tub waste outlets, a curb 1 inch lower than the sides and 2 to 9 inches above the drain, receptor floors sloped 1/8 to 1/2 inch per foot, a compartment of at least 1,024 square inches that holds a 30 inch circle, a built-in-place pan lined 3 inches above the curb and pitched 1/4 inch per foot to weep holes, and a 2 inch, 15 minute pan test.

Key Takeaways

  • CPC 408.4: showers and tub-showers need individual control valves of the pressure balance, thermostatic, or combination type, installed at the point of use.
  • CPC 408.4.2 and 409.4: water from an individual showerhead and from a bathtub filler is limited to 120 F.
  • CPC 408.3: showerheads and body sprays are limited to 1.8 gpm at 80 psi, and a hand-held shower counts as a showerhead.
  • CPC 408.5 and 409.2: shower waste outlet and tailpiece at least 2 inches; bathtub at least 1-1/2 inches.
  • CPC 408.6: a finished curb is at least 1 inch lower than the sides and back, 2 to 9 inches deep from its top to the top of the drain, and the receptor floor slopes 1/8 to 1/2 inch per foot to the drain.
  • CPC 408.7: at least 1,024 square inches of floor, able to hold a 30 inch circle, maintained to 70 inches above the drain; a receptor at least 30 by 60 inches is exempt.
  • CPC 408.8: a built-in-place pan is lined to at least 3 inches above the curb, pitched 1/4 inch per foot to weep holes, and never nailed less than 1 inch above the curb.
  • CPC 408.8.5: test the pan by filling it at least 2 inches deep for at least 15 minutes.

Why This Matters

Showers and tubs combine three kinds of code rules: scald protection, water conservation, and waterproofing. Most of them live in CPC Sections 408 (showers) and 409 (bathtubs and whirlpool bathtubs). Many of the numbers people quote on the job, like a standard valve height, are not in the code at all. This lesson keeps the ones that are.

Shower and Tub-Shower Valves (CPC 408.4)

  • Showers and tub-shower combinations have individual control valves of the pressure balance, thermostatic, or combination pressure balance and thermostatic type. They protect against scald and thermal shock at the rated flow of the installed showerhead.
  • The valves are installed at the point of use and comply with ASSE 1016/ASME A112.1016/CSA B125.16 or ASME A112.18.1/CSA B125.1.
  • Temperature limit (408.4.2): the water from an individual showerhead is limited to 120 F, by an ASSE 1016 valve that is field-adjusted to that maximum, or whose handle position, stop, or limiting control is set per the manufacturer's instructions.
  • Gang showers (408.4.1 and 408.4.2): where supplied by one temperature-controlled pipe, a mixing valve complying with ASSE 1069, field-adjusted to the maximum.
  • Temperature-actuated flow reduction devices (408.4.3) comply with ASSE 1062 but cannot be used alone as a substitute for the required shower valve or tub temperature limiting.
  • Single-handle valves in showers and tub-showers follow the hot and cold markings on the fitting (417.5).

How the two main types work: a pressure balance valve reacts to a change in hot or cold supply pressure, such as a toilet flushing, and adjusts so the mix does not spike. A thermostatic valve senses the mixed water temperature and holds the setting. Either type still has to be set so the showerhead delivers no more than 120 F.

Valve height is not a CPC number. Set it from the plans, the manufacturer's instructions, and any accessibility rules that apply.

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