Chapter 4 of 618% of exam

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

A minimum of 15 inches is required from the centerline of a water closet or bidet to any side wall, partition, or vanity, so the fixture is usable and cleanable.

2022 California Plumbing Code (CPC) §402.5

Water closet front clearance

At least 24 inches of clear space is required in front of a water closet, urinal, or bidet to allow approach and use.

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) §402.2

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 a water-seal trap placed as close as practical to the fixture outlet, with limited exceptions such as fixtures that already include an integral trap.

2022 California Plumbing Code (CPC) §1001.1

One trap per fixture

A fixture may not be double-trapped, and generally one trap serves one fixture, though a set of like fixtures such as a three-compartment sink may be served under specific allowances.

2022 California Plumbing Code (CPC) §1002.1

Water closet connection

A water closet is secured to a listed closet flange and sealed with a gasket or wax-type seal so the joint is gas-tight and water-tight.

2022 California Plumbing Code (CPC) §402.2

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

Walls and floors around fixtures such as showers and tubs must be finished with smooth, hard, non-absorbent materials to a required height to resist water damage.

2022 California Plumbing Code (CPC) §408.5

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) §608.3

Relief discharge routing

The T&P discharge pipe must be full size, run downward or to an approved point of disposal, terminate near the floor or outside, and end with an air gap; it may not be trapped, threaded at the end, or connected directly to the drainage system.

2022 California Plumbing Code (CPC) §608.5

Two-strap seismic bracing

Water heaters must be anchored or strapped to resist earthquake motion, using strapping at points in the upper and lower thirds of the tank while keeping the lower strap a safe distance 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

No valve of any kind may be installed between the water heater and its relief valve, or in the relief discharge line, because any obstruction could defeat the safety device.

2022 California Plumbing Code (CPC) §608.4

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 located so that leakage would damage the structure, it must sit in a corrosion-resistant pan piped by a drain line to an approved discharge point.

2022 California Plumbing Code (CPC) §507.4

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) §507.10

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.