Water Heater Safety

A water heater is a tank of hot water under pressure, often next to a gas flame. When it’s set too hot, vented badly, or its safety valve doesn’t work, it can scald, poison with carbon monoxide, start fires, or in rare cases explode.

• Homeowners
• Tenants

Temperature

Set the water heater to about 120°F. Water at 140°F can cause a serious scald on a child’s skin in seconds. If someone in the home needs hotter water for medical reasons, ask a plumber about anti-scald mixing valves at the faucets.

The relief valve

• The temperature and pressure (T&P) relief valve opens if the tank gets too hot or pressure gets too high.
• Its discharge pipe should run down to within a few inches of the floor or to a drain, never be capped or plugged, and never be reduced in size.
• Test it about once a year as the manufacturer directs: put a bucket under the pipe and lift the lever briefly. Hot water should flow and stop when released. If it doesn’t, call a plumber.
• A valve that keeps dripping is a warning sign; have it checked.

Gas water heaters

• Keep a carbon monoxide alarm nearby and on every level. See Smoke & CO Alarms.
• Make sure the vent pipe is connected, sloped up and not rusted, and that the area has combustion air.
• Keep gasoline, paint thinner, and other flammables far away. Vapors can ignite at the burner.
• In garages, older gas heaters are usually raised so the flame is off the floor, as codes typically require.
• If you smell gas, leave and call the gas company. See Gas Leaks.

Earthquake areas

Strap the water heater to wall studs with two straps (top and bottom third). A falling heater can break gas and water lines. Many western states require straps. See Earthquakes.

Yearly checklist

• Thermostat at about 120°F
• T&P valve tested and discharge pipe clear
• Tank drained or flushed to remove sediment, per the manufacturer
• No rust, leaks or water on the floor; consider a drain pan and a leak alarm
• Vent and flame checked on gas units
• Nothing stored against the heater

Last updated: October 2, 2026