How to Flush a Tank Water Heater (and Why It Matters)

Water Heaters · Published 2026-09-23 by the JetStream Plumbers team

Every tank water heater collects sediment. In South Florida, where the water is naturally hard, that buildup happens faster. Flushing the tank once a year helps it heat efficiently and last longer.

Why sediment is a problem

• It insulates the water from the burner or lower element, so the heater runs longer to heat the same water.
• It causes the rumbling or popping sounds many older tanks make.
• It can clog the drain valve and, in electric units, bury the lower element and cause it to burn out.

The basic process

1. Turn off the power (electric) or set the gas control to "pilot" or "off."
2. Close the cold-water supply valve on top of the tank.
3. Attach a garden hose to the drain valve at the bottom and run it to a floor drain or outside.
4. Open a hot-water faucet in the house to let air in, then open the drain valve.
5. Once the tank drains, briefly open the cold supply to stir up and flush remaining sediment. Repeat until the water runs clear.
6. Close the drain valve, refill the tank completely (until water flows steadily from the open faucet), then restore power or gas.

Important: never turn the power back on to an electric heater before the tank is full, or you can burn out the elements instantly.

When to call a pro instead

• The tank hasn't been flushed in many years. Heavy sediment can clog the valve, and old plastic drain valves can break or leak once opened.
• The drain valve drips after closing.
• You notice rust-colored water, a leak at the base or a corroded tank.

A plumber can also check the anode rod, which protects the tank from corrosion and is often ignored until it's too late. During a maintenance visit, it's a quick inspection that can add years to a tank's life.

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