How to Turn Off a Water Heater (Gas & Electric)

01Turning off a gas water heater

A gas water heater is controlled by the dial on the gas control valve, the boxy unit near the bottom of the tank where the gas line enters. Rotating that dial to "OFF" shuts the gas to both the burner and the pilot. Rotating it to "Pilot" instead stops the main burner but keeps the small pilot flame lit, which is what you want for routine work like draining, since relighting is avoided.

For a full shutdown, also close the manual gas shutoff valve on the gas pipe running to the unit: a quarter turn so the handle sits across (perpendicular to) the pipe means closed. Use the full "OFF" plus the gas valve when leaving for an extended trip or when there is any concern about the unit.

• ·Routine draining: dial to "Pilot"
• ·Full shutdown: dial to "OFF"
• ·Extra safety: turn the manual gas valve perpendicular to the pipe

02Turning off an electric water heater

An electric water heater has no dial to turn; you cut its power at the breaker panel. Find the double-pole breaker (it spans two slots) labeled for the water heater and switch it firmly to OFF. If nothing is labeled, the water heater breaker is usually a 30-amp double-pole; trace it or test by checking whether the elements stop heating.

Some installations also have a disconnect switch or a junction box right at the heater, but the breaker is the reliable cutoff. Never just rely on the thermostat dial inside the access panel; that does not de-energize the elements. The breaker does.

03Shutting off the water supply

Heat and power off stops the heater from making more hot water, but water can still flow into the tank. The cold-water shutoff valve sits on top of the heater on the inlet line (often the right-hand pipe, sometimes blue-handled). Turn a lever valve a quarter turn so it sits across the pipe, or turn a round gate valve fully clockwise.

If that valve will not budge or there is no dedicated valve, shut off the main water supply to the house instead. A leaking heater is the most common reason people search for how to do this, and our guide to what to do by leak location walks through diagnosing the leak after you have stopped the flow.

04The emergency shutoff sequence

When a heater is leaking, spraying, or you smell gas, work in a fixed order. Smell gas: leave the area, do not touch switches, and call the gas utility from outside; do not try to operate the valve in a gas-filled space. For a leak or rupture with no gas smell, kill the heat source first, then stop the water.

The order matters because of what happens next. Shut the power or gas, then close the cold-water inlet, then open a hot tap to relieve pressure, then drain through a hose if needed. Stopping the water without first cutting power is what causes element damage, which is the same reason power-off comes first when you flush a water heater.

• ·Smell gas: leave, call the utility from outside, touch nothing
• ·Leak, no gas: cut heat/power first
• ·Then close the cold-water inlet valve
• ·Then open a hot tap to relieve pressure, and drain if needed

05Why power-off-first matters when draining

The single most important habit is cutting heat before water. On an electric heater, an element that energizes while exposed to air, after the tank has partly drained, burns out in seconds; this is a dry fire, and it turns a no-cost shutoff into a repair. On gas, running the burner against a draining tank is pointless and overheats the steel.

So the sequence for any draining job is always heat off, then water off, then drain. If a dry-fired element does cook, replacing one is a routine fix, and our water heater repair cost guide shows what that and other common parts run. But the whole problem is avoided by flipping the breaker or the gas dial first.