Electric Water Heaters in Seattle, WA

To improve safety, prevent water damage, and bring existing electric water heater installations into compliance with applicable plumbing and building requirements, the following upgrades are recommended or required where applicable:

1. Earthquake Strapping
Water heaters shall be properly secured with approved seismic straps to prevent movement or overturning during an earthquake. Strapping should be installed in accordance with applicable local code requirements and manufacturer specifications.

2. Thermal Expansion Tank
Where required by the plumbing system configuration, an approved thermal expansion tank shall be installed on the cold-water supply serving the water heater. The expansion tank must be properly sized, supported, and pre-charged according to system pressure and manufacturer requirements.

3. Water Heater Drain Pan and Drain
A properly sized and approved drain pan shall be installed beneath the water heater where required. The pan drain shall discharge to the exterior of the building or to an approved drainage location within the building.

Important: The drain shall not terminate in a crawlspace.

4. Temperature and Pressure (T&P) Relief Valve and Discharge Pipe
The water heater shall be equipped with a properly rated temperature and pressure relief valve. The T&P valve shall be rated at 150 PSI, where applicable, and shall have an approved discharge pipe.

The discharge pipe shall terminate:

• Outside the building; or
• Not less than 6 inches above the flood-level rim of an approved drain, where permitted by applicable code.

Important: The T&P discharge pipe shall not terminate in a crawlspace.

Possible Low-Level T&P Configuration

An exemption or alternate installation may be permitted in certain jurisdictions where the building’s main water line is equipped with an approved low-level T&P relief valve rated at 125 PSI. Where this configuration is specifically permitted by the applicable authority having jurisdiction, the water heater discharge piping may be allowed to terminate within the building.

A 125 PSI low-level T&P valve primarily addresses excessive water pressure. It does not provide the same protection against excessive water temperature as a properly installed water-heater T&P relief valve.

For this reason, a low-level pressure relief arrangement should not be considered a substitute for appropriate temperature protection. Installation of a water heater flood-stop/leak-detection device is strongly recommended to help limit property damage in the event of a water heater or plumbing failure.

5. Thermostatic Mixing Valve (Recommended)
Installation of an approved thermostatic mixing valve is recommended to control the temperature of water delivered from the water heater and reduce the risk of scalding.

Proper temperature management can also support hot-water system hygiene and help reduce conditions that may contribute to the growth of Legionella bacteria. A mixing valve should be properly sized, installed, adjusted, and maintained in accordance with the manufacturer’s instructions and applicable plumbing requirements.

Final Recommendation

All safety devices, relief valves, discharge piping, drain pans, expansion tanks, seismic restraints, and related components should be installed by a qualified plumbing professional and verified against currently adopted local plumbing and building codes. Requirements can vary by jurisdiction, installation type, and existing system conditions.

Where there is any uncertainty regarding an exemption or alternate installation method, the requirements should be confirmed with the local Authority Having Jurisdiction (AHJ) before work is performed.

Safety Note: Relief valves and their discharge piping are critical safety components and must never be capped, plugged, reduced, or otherwise obstructed.