How to Flush Your Water Heater
Every gallon of water that enters your tank carries tiny mineral particles. They settle to the bottom and bake into a rock-hard layer that insulates the burner from the water, wastes energy, and rusts the tank from the inside out. A one-hour flush once a year removes the sediment.
- cost
- $0 DIY · $100–$200 pro
- time
- 45–60 minutes
- frequency
- Once a year
- difficulty
- Easy
- diy or pro
- DIY
Why it matters
A typical water heater is rated for 10–12 years, but the average actually lasts only 8–10 because sediment is allowed to build up. Annual flushing can extend life to 15+ years and recovers 10–20% of lost efficiency, depending on water hardness.
How often
- Hard water area: every 6 months
- Soft water area: once a year
- Tankless units: descale once a year with vinegar (different procedure)
What you'll need
- A standard garden hose
- A bucket
- Adjustable wrench or pliers
- 45–60 minutes (most of it waiting)
Step-by-step (gas or electric tank)
- Turn off power. Gas: set the dial to "Pilot." Electric: flip the breaker for the water heater.
- Turn off the cold-water inlet at the valve above the tank.
- Open a hot-water faucet in the house (kitchen sink works). This prevents a vacuum and lets the tank drain freely.
- Connect a garden hose to the drain valve at the bottom of the tank. Run it to a floor drain, driveway, or large bucket. Caution: the water is scalding.
- Open the drain valve. Let it run until the water is clear, usually 10–20 minutes. If sediment clogs the valve, briefly open the cold-water inlet to stir things up.
- Close the drain valve and disconnect the hose.
- Turn the cold-water inlet back on. Leave the indoor faucet open until water flows steadily and air stops sputtering out — that means the tank has refilled.
- Restore power. Wait 30–45 minutes before expecting hot water.
When to call a pro
If the drain valve won't open or won't close again, or if you see rust-colored water continuing for more than 30 minutes of flushing, the tank may be near end of life. Get a plumber to assess.
Frequently asked questions
How often should I flush my water heater?
Once a year for most homes. Every 6 months if you have hard water. Tankless units need annual descaling, which is a different procedure using vinegar.
Will flushing extend the life of my water heater?
Yes — significantly. Sediment buildup is the leading cause of premature tank failure. Annual flushing can extend life from the typical 8–10 years to 15+.
Is flushing a water heater dangerous?
The water coming out is scalding hot — direct the hose to a safe drain, not at people, pets, or plants. Other than that it's straightforward DIY.
What if no water comes out when I open the drain valve?
Either the valve is clogged with sediment (briefly open the cold-water inlet to dislodge it) or you forgot to open a hot-water faucet upstairs (needed to break the vacuum).
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