How to replace a water heater

We'll replace the water heater from drain to reconnect—gas or electric.

What you'll need

At a glance

Shut off the water supply, gas or power, and drain the old tank before disconnecting.
Gas water heaters require proper venting—call a pro if the vent is damaged or you smell gas.
Disconnect the supply lines, gas line or electrical, and vent pipe; remove the old unit.
Set the new heater on a stand if required by code; connect supply, gas or electric, and vent.
Fill the tank before turning on power or gas; purge air from the lines and check for leaks.

Quick triage — pick your path

Choose the option that matches what you see. You can jump straight to that section.

Goal: Replace the water heater from drain to final test.

Goal: Make the unit safe to disconnect.

For gas: turn off the gas control and supply valve. For electric: turn off the circuit breaker.
Good: No gas flow or power. Proceed to Disconnect and remove.
Bad: Gas valve will not close—call the gas company or a plumber.

Goal: Free the old heater and remove it.

Disconnect supply lines, gas or electrical, and vent. Remove the old unit with a dolly.
Good: Space is clear. Proceed to Install the new heater.
Bad: Connections are corroded—use penetrating oil or call a plumber.

Goal: Position and connect the new unit.

Set the heater on a stand if required. Connect supply lines, gas or electric, and vent.
Good: All connections secure. Proceed to Fill and test.
Bad: Vent does not fit—do not use the heater; call a pro for venting.

Goal: Fill the tank, purge air, and verify no leaks.

Open the cold supply. Open a hot faucet to purge air. Check for leaks.
Light the pilot (gas) or turn on power (electric). Wait for hot water.
Good: Hot water at faucet; no leaks. Proceed to Verification.
Bad: Leak at a connection—tighten or replace the fitting. Gas odor—shut off gas and call a pro.

Call a plumber or gas technician if:

You smell gas at any point—evacuate and call 911 or the gas company from outside.
The vent is damaged or does not fit the new heater.
You are not comfortable with gas or electrical connections.
The water heater is in a confined space or requires permit work.

Reviewed by Blackbox Atlas

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