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How do you drain a water heater?

Updated August 2026

45–60 minutes · Easy DIY

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Draining a water heater is a 45–60 minute, Easy-DIY job: cut the power or gas, shut the cold-water inlet, run a garden hose from the drain valve to a floor drain or outside, open a hot tap upstairs to break the vacuum, then open the valve and let the tank empty. The only tools are a hose, a flathead screwdriver, and gloves. The steps below include the part most people skip, pulsing the cold inlet to stir up and flush the sediment that is the whole reason you're draining it.

What you need

Before you start: The water inside sits at 120–140°F and scalds on contact. Let the tank cool for at least 2 hours first, or run a long hot shower to draw the temperature down before you start. Never energize the electric elements or fire the gas burner while the tank is empty: a dry-fired element burns out in seconds, and a bone-dry gas tank can be damaged just as fast.

Steps

  1. Kill the heat. Flip the water heater's breaker for an electric unit, or turn the gas control to "pilot" (or off) for a gas unit, so the burner and elements cannot fire while the tank is empty.
  2. Shut the cold-water inlet valve on top of the tank (the handle or lever on the incoming line).
  3. Screw a garden hose onto the drain valve at the base of the tank and run the other end to a floor drain, a driveway, or downhill outside.
  4. Open a hot-water tap on an upper floor and leave it running. That breaks the vacuum so the tank can actually drain instead of gurgling to a stop.
  5. Open the drain valve (a flathead screwdriver turns the slotted plastic ones) and let the tank empty. Expect 30 to 40 gallons and warm, cloudy water at first.
  6. Once it stops, briefly reopen the cold inlet in short bursts. The incoming water stirs up the sediment on the tank floor; keep pulsing until the water leaving the hose runs clear.
  7. Close the drain valve, disconnect the hose, and reopen the cold inlet to refill. Keep that upstairs hot tap open until it runs a steady, air-free stream, then close it.
  8. Restore the power or gas only after the tank is full. Give it 30 to 60 minutes to reheat before you expect hot water.

Or hire it out

A plumber charges $100–200 to drain and flush a water heater as a standalone visit, and often folds it into an annual service call or a tune-up you're already paying for. The DIY version costs you a garden hose and an hour.

Done. Now the part everyone skips: doing it again on schedule. Log it in OnOtto and the next reminder for draining the water heater sets itself.

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Frequently asked questions

Do I have to drain the whole tank, or can I just flush it?

For routine sediment removal you don't need to fully empty it. Shut the cold inlet, drain a few gallons through the hose, then pulse the cold inlet on and off to blast the sediment out while the tank is still mostly full. Fully drain it only when you're replacing the anode rod, moving the unit, or shutting the house down for winter. A partial flush is faster and puts less stress on an old drain valve.

How often should I drain or flush a water heater?

Once a year for most homes, and every 6 months on hard water with no softener. Sediment builds faster than people think: in hard-water areas a tank can lay down a half-inch of mineral crust in a single year, which insulates the burner and wastes energy. The full schedule, with what changes the interval for your water, is on how often to flush a water heater.

My drain valve drips or won't fully close afterward. What now?

Common on the cheap plastic valves. First try seating it firmly, then cap the outlet with a garden-hose cap ($3) as a backstop. If it still weeps, replace it with a brass valve or ball-valve drain, a $15 part best swapped by a plumber while the tank is already drained. A valve that won't seat is also a nudge to check the tank's age, since it often shows up right when a tank is near the end of its life.

The water is still rusty or cloudy after draining. Is my tank shot?

Not necessarily. Cloudy usually just means stirred-up sediment, and it clears once you've refilled and run the taps. Persistent rust-brown water is more concerning: it points to a spent anode rod or a corroding tank. Check the anode rod first, since a $30 rod is what stands between the steel and rust, and weigh it against the tank's expected lifespan before spending on a full replacement.

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