Flush Sediment from a Water Heater
Category: Plumbing ·
Difficulty: Intermediate ·
Time: 2.3h ·
Estimated cost: $18
Tools needed
- 50-foot garden hose
- Bucket
- Pipe wrench
- Flathead screwdriver
- Work gloves
- Safety glasses
Materials needed
- Replacement plastic drain valve (if leaks) (1 ea)
- PTFE tape (1 roll)
- Garden hose washers (1 pk)
Execution steps
Cut heat
Gas: turn the thermostat dial to PILOT. Electric: flip the breaker for the heater off. Wait 30 minutes for water to cool somewhat.
Duration: 35 min
Shut cold water supply
Find the cold water valve on top of the tank. Close it.
Duration: 5 min
Hook up drain hose
Connect garden hose to the bottom drain valve. Route hose outside or to a floor drain. Lay it flat — gravity will do the work.
Duration: 10 min
Open relief and drain valve
Open the temperature/pressure relief valve at the top to break the vacuum. Then open the bottom drain valve. Water will start flowing.
Duration: 5 min
Flush until clear
Let drain fully (20-40 minutes). Then close the drain, open the cold supply briefly to stir sediment, then drain again. Repeat until water runs clear.
Duration: 1h
Refill and restart
Close drain valve. Open cold supply. Open a hot tap upstairs — when steady water flows from that tap (no sputtering air), tank is full. Close TPR. Restore power or relight pilot.
Duration: 25 min
Safety first
- Hot water from the tank scalds severely — wait for cooldown, wear long sleeves and gloves.
- NEVER open the drain valve without the TPR or a hot tap open, or you'll create a vacuum and crush the tank.
- If the plastic drain valve cracks, replace with a brass valve — much more reliable.
When to hire a pro
If sediment is so thick the tank won't drain (just trickles), the tank is at end of life — call a plumber for replacement.
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