How to drain sediment from the tank water heater
To drain sediment from a water heater, the Department of Energy says to run about a quart of water from your tank every 3 months and to follow your manufacturer's instructions. Use a hose on the drain valve, let the water run clear and close the valve. The water is hot enough to burn.
How often to drain a water heater
Sediment is minerals and grit that settle on the tank floor. It slows heat transfer, makes noise, can burn out electric elements and can overheat the bottom of a gas tank. Hard water makes it much worse.
| Job | How often | Source |
|---|---|---|
| Drain about a quart | Every 3 months | Department of Energy |
| Full flush | As your manual says. Hard water needs it more | Manufacturer |
| Test the temperature and pressure (T&P) relief valve | Once a year | Water Heater Rescue |
| Check the anode rod | No fixed date. Replace when about 6 inches of bare wire shows | Water Heater Rescue |
| Look for external leaks | Now and then | Water Heater Rescue |
A water softener changes the picture. It removes most of the minerals that form sediment, so flushing may not be needed. It also uses up the anode faster, so check the rod more often.
Be realistic about the results. Water Heater Rescue notes that sediment can keep building even with regular draining, because the domed tank bottom and gas flue get in the way of the flow.
What you need to drain sediment from a water heater
- A garden hose rated for hot water, or a bucket for a quart draw
- A flat screwdriver or pliers if the drain valve has no handle
- Heavy gloves and eye protection
- A spare hose washer
- A floor drain, or a place outside where hot water won't harm plants or people
- Your water heater manual, or the model number from the tank label
Set a safe temperature while you're at it. The Department of Energy suggests 120°F, which it describes as safe for most people. Keep kids and pets away from the drain hose, and don't aim it where someone could step in it.
Tankless heaters are a different job. Follow the maker's descaling instructions, and don't use these steps.
How to drain sediment from a water heater tank
- Read your manual first
Follow it over this list where they differ. Note how your model shuts down and restarts.
- Shut off the heat
Switch off the breaker for an electric tank, or set a gas control to vacation or pilot. Let very hot water cool for a few hours if you plan a full flush.
- Attach the hose
Thread it onto the drain valve at the bottom of the tank and run the free end downhill to a drain.
- Open the valve slowly
Let about a quart go for a routine draw. Expect cloudy water or flakes at first.
- Flush if you're due
Close the cold supply and open a hot tap to let air in, then drain. Open the cold supply in short bursts to stir up sediment.
- Close and refill
Shut the drain valve, turn on the cold supply and keep a hot tap open until water flows steadily with no sputtering.
- Restart the heat
Restore power or gas only once the tank is full. Check the drain valve for drips over the next hour.
Signs of water heater sediment and other tank trouble
- Rumbling or popping when the burner runs. That's usually sediment, and it's a sign you're overdue.
- Water that won't run clear after a long flush, or a hose that slows to a trickle. The valve may be clogged with sediment.
- A drain valve that drips after you close it. Try a hose cap, and if the drip continues, call a plumber.
- A T&P valve that won't let water through, won't stop running or keeps dripping for more than a few minutes. Replace it. This is a safety valve, and it can seize with scale.
- Water around the base of the tank, or rust on the tank itself. A leak from the tank body usually means replacement.
- Less hot water than you used to get. Sediment, a failed element or a worn dip tube can each be the cause.
- Rotten-egg smell in the hot water. Ask a plumber about the anode rod.
Drain a water heater yourself or call a plumber?
A quart draw is an easy DIY job, and so is a full flush on a newer tank with a sound valve. Stop and call a licensed plumber in these cases:
- You've never drained it and the tank is old. Valves left untouched for years can stick or refuse to close.
- You smell gas. Leave the house and call your gas utility from outside. Don't touch switches.
- The burner or pilot won't relight after the job.
- You see scorching near the burner, or soot on a gas tank.
- The cold shutoff valve won't turn. Water Heater Rescue warns that gate valves often fail when you need them.
- The T&P drain line needs changes. It has to run down and out, and code applies.
Gas work, venting and electrical work on a water heater are for licensed pros. Many towns require a permit to replace one.
What homeowners say about how to flush a water heater
Do one flush and look at what comes out. If it runs clear, owners and DIY pros say you can flush much less often. Gas tanks with hard water build up the most sediment and benefit most. (DIY Stack Exchange)
Where owners disagree: Owners and DIY pros don't follow a fixed calendar. Do one flush and judge by what comes out. Clear water means flush rarely, while gas tanks with hard water need it most. Some modern gas units hardly need it. (DIY Stack Exchange)
Water heater popping noise and other questions
How often should I drain my water heater?
The Department of Energy says to drain a quart every 3 months and to follow your manufacturer's advice. Many makers also call for a periodic full flush, especially in hard water areas.
Do I need to turn off the water heater to drain it?
For a full flush, yes. Turn off the power or set gas to vacation, because an electric element can burn out if it runs without water around it.
Why is my water heater popping or rumbling?
Sediment on the tank floor is the usual cause. Try a flush, and if the noise continues or you see leaks, have a plumber look at it.
Sources: U.S. Department of Energy, waterheaterrescue.com
General guidance for U.S. homes, not professional advice. For gas, electrical and structural work, call a licensed pro.