Hot Water Heaters | CPC § 504


The following California Plumbing Code sections revolve around the installation and maintenance of water heaters in a home. These laws are important for ensuring safety, efficiency, and longevity in the operation of water heaters.

First, let's define some terms that might be unfamiliar:

  • Fuel-Burning Water Heater: This type of water heater burns fuel (such as gas or oil) to heat the water. Direct vent types draw air from outside for combustion and vent exhaust gases directly outside.
  • Listed: A device or appliance that has been tested and meets specific safety standards by a recognized testing laboratory. Per the CPC Listed is defined as "All products that appear in a list published by an approved testing or listing agency. For additional information, see Health and Safety Code Section 17920(h)."
  • Combustion Air: The air needed by a fuel-burning appliance for complete combustion. This is usually drawn from outside to ensure good quality air for efficient and clean burning.
  • British thermal units (Btu): This is a unit of heat energy. In the context of water heaters, it relates to the heater's output capacity.
  • Seismic Provisions: These are measures taken to protect buildings and their components (like water heaters) from damage during earthquakes.
  • Strapping: A method of securing a water heater by using metal bands or straps to prevent it from moving or tipping over.
  • Drainage Pan: A pan placed under a water heater to catch any leaking water and direct it to a drain, thereby preventing water damage to the property.
  • Flammable Vapor Ignition Resistant: A feature in some water heaters that prevents the ignition of flammable vapors outside the water heater.

The following sections of code will go into more detail about each aspect of water heater installation, from where it can be installed to how it must be strapped for safety, especially in earthquake-prone areas. It will cover requirements for the devices that control its operation and prevent malfunctions, the ground support for the heater, the need for a drainage pan in certain locations, safety provisions for installation in garages, and the importance of following manufacturer's instructions. While the terms and code language may seem complex, they are essentially guidelines designed to ensure your water heater functions safely and efficiently.


Water heaters shall be installed in accordance with CPC 504. 


Water heater installations in bedrooms and bathrooms shall comply with one of the following:

  1. Fuel-burning water heaters shall be permitted to be installed in a closet located in the bedroom or bathroom provided the closet is equipped with a listed, gasketed door assembly and a listed self-closing device. The self-closing door assembly shall meet the requirements of CPC 504.1.1. The door assembly shall be installed with a threshold and bottom door seal and shall meet the requirements of CPC 504.1.2. Combustion air for such installations shall be obtained from the outdoors in accordance with CPC 506.4. The closet shall be for the exclusive use of the water heater.
  2. Water heater shall be of the direct vent type.


The clearances shall not be such as to interfere with combustion air, draft hood clearance and relief, and accessibility for servicing. Listed water heaters shall be installed in accordance with their listings and the manufacturer's installation instructions.

Temperature, Pressure, and Vacuum Relief Devices

Temperature, pressure, and vacuum relief devices or combinations thereof, and automatic gas shutoff devices shall be installed in accordance with the terms of their listings and the manufacturer's installation instructions. A shutoff valve shall not be placed between the relief valve and the water heater or on discharge pipes between such valves and the atmosphere. The hourly British thermal units (Btu) (kW•h) discharge capacity or the rated steam relief capacity of the device shall be not less than the input rating of the water heater. Discharge piping shall be installed in accordance with CPC 608.5.

Seismic Provisions

Water heaters shall be anchored or strapped to resist horizontal displacement due to earthquake motion. Strapping shall be at points within the upper one third (1/3) and lower one-third (1/3) of its vertical dimensions. At the lower point, a minimum distance of four (4) inches (102 mm) shall be maintained above the controls with the strapping. All new and replacement water heaters, and all existing residential water heaters shall be braced, anchored, or strapped to resist falling or horizontal displacement due to earthquake motion. At a minimum, any water heater shall be secured in accordance with the California Plumbing Code, or modifications made thereto by a city, county, or city and county pursuant to Section 17958.5 of the Health and Safety Code.

Ground Support

A water heater supported from the earth shall rest on level concrete or other approved base extending not less than 3 inches (76 mm) above the adjoining ground level.

Drainage Pan

Where a water heater is located in an attic, in or on an attic ceiling assembly, floor-ceiling assembly, or floor-subfloor assembly where damage results from a leaking water heater, a watertight pan of corrosion-resistant materials shall be installed beneath the water heater with not less than 3/4 of an inch (20 mm) diameter drain to an approved location. Such pan shall be not less than 1 ½ inches (38 mm) in depth.

Installation in Residential Garages

Appliances in residential garages and in adjacent spaces that open to the garage and are not part of the living space of a dwelling unit shall be installed so that all burners and burner-ignition devices are located not less than 18 inches (457 mm) above the floor unless listed as flammable vapor ignition resistant. Appliances installed in garages, warehouses, or other areas subject to mechanical damage shall be guarded against such damage by being installed behind protective barriers or by being elevated or located out of the normal path of vehicles.

Installation Instructions

The installing agency shall conform to the appliance and equipment manufacturer's recommendations in completing an installation. The installing agency shall leave the manufacturer's installation, operating, and maintenance instructions in a location on the premises where they are readily available for reference and guidance of the Authority Having Jurisdiction, service personnel, and the owner or operator.