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Fixtures & Water Heaters

Plumbing fixtures and water heaters are where the system meets the user, and they are among the most heavily tested topics on the C-36 exam. This chapter covers how fixtures must be spaced, counted, and connected, and then works through the many safety requirements that surround water heater installation: temperature and pressure relief, seismic strapping, drain pans, combustion air, venting, and thermal expansion control. Nearly all of these requirements exist to prevent scalding, explosion, flooding, or carbon monoxide poisoning, so examiners expect you to know not just the numbers but the reasons behind them.

Fixture Clearances and Counts

Every fixture needs enough space around it to be used and cleaned, and enough fixtures must be provided for the number of people a building serves. The code sets minimum clearances measured from the center of the fixture to walls and adjacent fixtures, and it publishes tables that translate building occupancy into a required count of water closets, lavatories, and other fixtures. Getting these minimums right is the difference between a plan that passes and one that is rejected.

Water closet side clearance

No water closet or bidet shall be set closer than 15 inches from its centre to a side wall or obstruction, nor closer than 30 inches centre to centre to a similar fixture. Paper dispensers and accessibility grab bars are not counted as obstructions.

2022 California Plumbing Code (CPC) §402.5

Water closet front clearance

The clear space in front of a water closet, lavatory, or bidet shall be not less than 24 inches. A urinal is not on that list: no urinal shall be set closer than 12 inches from its centre to a side wall or partition, nor closer than 24 inches centre to centre.

2022 California Plumbing Code (CPC) §402.5

Fixtures sized to occupancy

The minimum number of plumbing fixtures for a building is determined by its occupancy type and load; the code's fixture-count tables must be consulted rather than guessing.

2022 California Plumbing Code (CPC) §422.1

Separate facilities by sex

Except where specifically exempted for small occupancies, separate toilet facilities are generally required for each sex based on the calculated occupant load.

2022 California Plumbing Code (CPC) §422.2

Fixtures must be accessible

Fixtures are installed so that all connections, joints, and traps remain accessible for inspection, cleaning, and repair without demolition.

2022 California Plumbing Code (CPC) §402.1

Fixture Connections and Materials

A fixture is only as good as its connection to the drainage and water systems. Each fixture must have a trap to block sewer gas, a proper supply connection with a shutoff, and a water-tight, durable joint where it meets the floor or wall. Surfaces that receive splashing water must be smooth, non-absorbent, and easy to clean.

Every fixture is trapped

Each plumbing fixture must be separately trapped by an approved type of liquid seal trap, except fixtures with integral traps, and not more than one trap is permitted on a trap arm. The vertical distance between the fixture outlet and the trap weir must be as short as practicable and the tailpiece must not exceed 24 inches.

2022 California Plumbing Code (CPC) §1001.2

One trap per fixture

No fixture shall be double trapped. One trap may serve a set of not more than three single-compartment sinks or laundry tubs of the same depth, or three lavatories immediately adjacent in the same room, where the waste outlets are not more than 30 inches apart and the trap is centrally located.

2022 California Plumbing Code (CPC) §1001.2 and §1004.1

Water closet connection

A water closet is secured to an approved closet ring (closet flange) approximately 7 inches in diameter that, with the soil pipe, presents a 1-1/2 inch wide face to receive the fixture gasket or closet seal; a caulked-on ring must be not less than 1/4 of an inch thick and not less than 2 inches in overall depth.

2022 California Plumbing Code (CPC) §402.6 and §402.6.1

Individual shutoff supply

Fixtures are supplied with water through connections that include an accessible shutoff so the fixture can be isolated for service without shutting down the whole building.

2022 California Plumbing Code (CPC) §605.5

Non-absorbent surfaces

Shower compartments and the walls above a bathtub with an installed showerhead must be finished with a smooth, non-absorbent surface to a height of not less than 72 inches above the drain inlet. Walls within 2 feet of a service sink, urinal, or water closet must be smooth, hard, and non-absorbent to not less than 4 feet above the floor, except in dwelling and sleeping units and in a non-public toilet room with not more than one water closet.

2022 California Building Code (CBC), Title 24 Part 2, §1210.2

Water Heater Relief, Discharge, and Seismic Support

A storage water heater is a pressure vessel holding scalding water, so the code layers several protections on it. A temperature and pressure (T&P) relief valve prevents the tank from exploding if the thermostat fails; a properly routed discharge pipe carries any released hot water safely to a place it cannot injure someone. In California's seismic zones, the tank must also be strapped so it cannot topple, break its gas or water lines, and start a fire or flood.

T&P relief valve required

Every storage water heater must be protected by an approved, listed temperature and pressure relief valve that opens on excess temperature or pressure to prevent tank rupture.

2022 California Plumbing Code (CPC) §504.4, §504.5 and §504.6

Relief discharge routing

The relief discharge pipe must be not less than the size of the valve outlet, run with no valves, obstructions or means of isolation, and discharge by gravity through an air gap into the drainage system or outside the building, ending not more than 2 feet and not less than 6 inches above the ground and pointing downwards. It must not be trapped, must not be threaded at its terminal end, and must not discharge into the water heater's pan.

2022 California Plumbing Code (CPC) §608.5

Two-strap seismic bracing

Water heaters must be anchored or strapped to resist horizontal displacement due to earthquake motion, with strapping at points within the upper one-third and the lower one-third of the tank's vertical dimension, and at the lower point not less than 4 inches maintained above the controls.

2022 California Plumbing Code (CPC) §507.2

Discharge to safe location

The relief discharge must terminate where escaping hot water and steam are readily visible and cannot scald a building occupant.

2022 California Plumbing Code (CPC) §608.5

No shutoff on relief line

Each pressure relief valve must be an approved automatic type with a drain, set at not more than 150 psi. No shutoff valve may be installed between the relief valve and the system, nor on the discharge pipe between the valve and the atmosphere, because any obstruction could defeat the safety device.

2022 California Plumbing Code (CPC) §608.4 and §504.6

Drain Pans, Combustion Air, Venting, and Expansion

Water heaters fail eventually, and when they leak the water must be caught and drained away from finished space. Fuel-fired heaters also need air to burn cleanly and a vent to carry combustion gases—including deadly carbon monoxide—safely outdoors. Finally, because heated water expands, a closed system with a check valve or backflow preventer needs a place for that pressure to go, which is the job of a thermal expansion tank.

Drain pan where leakage causes damage

Where a water heater is in an attic, in or on an attic ceiling assembly, a floor-ceiling assembly, or a floor-subfloor assembly and damage would result from a leak, a watertight pan of corrosion-resistant material must be installed beneath it, not less than 1-1/2 inches in depth, with a drain of not less than 3/4 of an inch in diameter run to an approved location.

2022 California Plumbing Code (CPC) §507.5

Adequate combustion air

Fuel-burning water heaters must receive enough air for complete combustion and proper venting; an unconfined space or engineered openings must supply that air.

2022 California Plumbing Code (CPC) §506.0

Approved venting of gases

Combustion products from a fuel-fired water heater must be carried to the outdoors by an approved vent or chimney sized and installed to prevent spillage of carbon monoxide indoors.

2022 California Plumbing Code (CPC) §509.0

Thermal expansion control

On a closed water system—one with a check valve, pressure reducing valve, or backflow preventer—an expansion tank or similar device must absorb the pressure increase from heating so relief valves do not weep.

2022 California Plumbing Code (CPC) §608.3

Ignition source elevation in garages

A fuel-fired water heater in a garage must have its ignition source elevated above the floor unless it is a listed flammable-vapor-ignition-resistant unit, to reduce the risk of igniting spilled gasoline vapors.

2022 California Plumbing Code (CPC) §507.13

Flush Rates and CALGreen Water Efficiency

California limits how much water fixtures may use to conserve a scarce resource. The CALGreen code and the state's plumbing standards cap flow and flush volumes for toilets, urinals, faucets, and showerheads. A C-36 contractor must install fixtures that meet these maximum rates, because non-compliant fixtures will fail inspection and cannot legally be sold or installed in the state.

Water closet flush limit

Tank-type toilets are limited to a maximum effective flush volume of 1.28 gallons per flush under California efficiency standards.