How to Flush a Tank Water Heater

A homeowner guide from Drain Edge Rooter, a licensed plumbing company in Rialto, CA (C-36 #1078977). Open 24/7, call anytime: (909) 927-3194.

Hard water is common across the Inland Empire. As water heats in a tank, minerals settle to the bottom as sediment. Over time, that sediment can cause rumbling or popping noises, reduce how much hot water you get, and make the heater work harder. Flushing the tank periodically helps remove some of that buildup. Always check your water heater manufacturer's instructions for your specific model.

Safety first

Water in the tank is hot enough to scald. Wear gloves and closed shoes, keep children and pets away, and point the hose somewhere hot water can safely drain. If your water heater is very old, the drain valve may be brittle; if you are not comfortable working on it, call a plumber.

What you need

A garden hose.
A flathead screwdriver (some drain valves need one).
Gloves and a bucket.

Step-by-step

Turn off the heat. For a gas heater, turn the gas control to the pilot or vacation setting (or off, per the manufacturer). For an electric heater, turn off the breaker.
Turn off the cold water supply valve on top of the heater.
Let the water cool for a while if you can, to reduce the scalding risk.
Attach a garden hose to the drain valve near the bottom of the tank and run it outside or to a floor drain.
Open a hot water faucet in the house to let air in so the tank drains.
Open the drain valve and let the tank drain. Watch for sediment in the water.
Flush with fresh water. With the drain still open, turn the cold supply on for a short time to stir up and push out remaining sediment. Repeat until the water runs mostly clear.
Close the drain valve and remove the hose.
Refill the tank by turning the cold supply back on. Leave the hot faucet open until water flows steadily without sputtering air.
Restore heat only after the tank is full. Turning on an electric heater with an empty tank can burn out the elements.

Watch: tank water heater flush in Colton, CA

If the drain valve will not close or drips

Sometimes sediment keeps the valve from sealing. Open and close it a few times to clear it. If it still drips, put a hose cap on it and call a plumber about replacing the valve.

Tankless water heaters

Tankless units are not flushed the same way. They need periodic descaling, typically by circulating a descaling solution through the unit with service valves. Follow the manufacturer’s instructions or have a plumber do it, especially in hard-water areas.

Know your water heater

Look for the label on the side of the tank. It lists the model, capacity, fuel type and often a manufacture date coded in the serial number. Keep a note of it on your phone, along with the location of the gas valve, the breaker and the cold supply valve. If you ever need service, that information saves time on the phone.

Also check the area around the heater. Many California installations need seismic straps, a proper temperature and pressure relief discharge line, and, on gas units, correct venting and clearance. If anything looks missing, loose or corroded, have a plumber take a look.

Signs it is time to call a pro

Water leaking from the tank body itself (usually means the tank needs replacement).
Rusty or discolored hot water.
No hot water or a pilot that will not stay lit.
A gas smell. Leave the house and call the gas company first.
The temperature and pressure relief valve is leaking.
Loud noises that continue after flushing.

Drain Edge Rooter is open 24/7, so call anytime at (909) 927-3194.

Related services and areas

Related services: Water Heater Service, Gas Line Repair. We serve the whole Inland Empire, including plumber in Fontana, plumber in Ontario, plumber in Rancho Cucamonga, plumber in Highland. See all homeowner plumbing guides.