Knowing how to shut off your water heater is one of those things you don’t need often — until you do, and then you need to know it immediately. A leaking tank, a plumbing repair that requires cutting the water supply, a long vacation, or a gas smell near the unit are all situations where a fast, correct shutoff matters.
The procedure differs by fuel type and unit type. Here’s a clear guide for each.
Gas Tank Water Heater
Gas water heaters have a thermostat dial on the gas valve — the control box at the front of the unit where the gas supply line connects.
For routine situations (vacation, maintenance, plumbing work): Turn the thermostat dial to the “Pilot” position. This keeps the pilot light burning without firing the main burner. The unit stops heating water but maintains the pilot so it’s easy to restore when you return. This is the right setting for anything that isn’t an emergency.
For extended shutoff (more than a week, or unit going out of service): Turn the dial to “Off”. This extinguishes the pilot light and shuts off all gas to the unit. You’ll need to relight the pilot when you restore service. Turn off the gas shutoff valve on the supply line — typically a ball valve or lever valve on the gas pipe leading to the unit. Turn it perpendicular to the pipe to close.
In an emergency (gas smell, visible leak, fire): Don’t touch the water heater controls. Leave the house, don’t flip any switches, and call PG&E (1-800-743-5000) from outside. Let them shut off the gas.
To also shut off the water supply to the tank: close the cold water inlet valve on the pipe entering the top of the unit (turn clockwise). This stops water flowing into the tank without affecting the rest of the house’s water supply.
Electric Tank Water Heater
Electric water heaters don’t have a gas valve or pilot light. The shutoff is at the electrical panel.
Turn off the circuit breaker dedicated to the water heater — typically a double-pole 30-amp breaker labeled “water heater” in the panel. Flip it to the Off position.
Important: Never run an electric water heater with an empty or partially drained tank. The heating elements are submerged in water during normal operation — exposed elements burn out within minutes. If you’re draining the tank for maintenance or a repair, turn off the breaker first and confirm the power is off before draining.
To shut off the water supply: close the cold water inlet valve at the top of the unit.
Tankless Water Heater (Gas)
Tankless units don’t store water, so there’s no tank to worry about — but the gas and water supply still need to be addressed for maintenance or emergencies.
Gas shutoff: Locate the dedicated gas shutoff valve on the gas supply line to the unit (separate from the main gas shutoff for the house). Turn it perpendicular to the pipe to close.
Water shutoff: Most tankless units have isolation valves on both the cold water inlet and the hot water outlet — typically lever-style valves installed during setup. Close both. If your unit doesn’t have isolation valves, close the main cold water supply to the house.
Power: Gas tankless units still require electricity for the igniter, controls, and fan. Turn off the dedicated circuit breaker for the unit.
Tankless Water Heater (Electric)
Turn off the circuit breaker for the unit — electric tankless heaters draw significant amperage and will have a dedicated breaker, sometimes more than one depending on the unit size.
Close the isolation valves on the inlet and outlet connections if installed, or the main cold water supply.
Shutting Off the Water Supply to the Tank Only
In some situations — a leak at a fitting, a repair that only involves the water heater — you want to stop water flow to the unit without affecting the rest of the house.
The cold water inlet shutoff valve on the pipe entering the top of the tank controls flow into the unit only. Closing it (turn clockwise for a gate or globe valve; perpendicular to the pipe for a ball valve) stops new water from entering. Water already in the tank remains there.
If this valve is corroded or doesn’t close fully — common in older Santa Cruz homes — don’t force it. A stuck or partially closed shutoff valve can break, and then you’re dealing with water spraying from the connection. Call a plumber to replace the valve rather than force it.
When to Shut Off the Water Heater
Going on vacation: Gas units to “Pilot”; electric units leave on or turn to the lowest setting (unnecessary to fully power down for a week or two). Fully shutting off isn’t necessary for short trips.
Extended vacancy or rental turnover: Gas to “Off” and close the gas supply valve; electric breaker off. Also close the cold water inlet to prevent any slow leaks from filling a failed tank.
Plumbing work: Depends on the scope. If you’re working on pipes connected to the water heater, close the cold water inlet and drain some tank pressure by opening a hot water tap first.
Leak from the tank or connections: Shut off the cold water inlet immediately, then address the heat source. If the tank itself is leaking from the bottom, this is a replacement situation — see our guide on water heater repair vs. replacement.
Gas smell near the unit: Don’t touch the unit. Leave the house and call PG&E.
Water Heater Service in Santa Cruz
Eco-Flow Plumbing Inc. handles water heater repair and replacement throughout Santa Cruz County — Santa Cruz, Live Oak, Aptos, Capitola, Soquel, Scotts Valley, Seabright, Felton, Boulder Creek, and Watsonville.
Contact Eco-Flow Plumbing to schedule service. Or call directly: (831) 818-6331.
