How often should I flush my water heater?
Last updated 12 October 2026
The short answer
At least once a year for a tank water heater, and more often where the water is hard. Montana State University Extension notes that some areas need monthly flushing while others need it only once a year. Check the temperature and pressure relief valve once a year too, and follow your heater's manual, which is the final word for your model.
Why flush it
Sediment settles at the bottom of the tank. Montana State University Extension says sediments “reduce both heating element efficiency and the overall capacity of the water heater.”
How it's done
- The drain valve is near the bottom of the tank.
- Open it and let the murky water drain into a bucket until it runs clear, usually after one to two gallons (Montana State University Extension). The water is hot.
- If the valve has not been opened in years, attach a garden hose to it the first time.
- For a full flush, follow the steps in your heater's manual.
Two more checks
- The temperature and pressure relief valve “should be checked annually” (Montana State University Extension).
- Temperature: the same guide suggests turning it down to 120°F.
Your manual decides
Intervals vary by maker and model. HavnOS's defaults are a flush and a relief-valve test once a year. On the Max plan it also finds your water heater's owner's manual and pulls the maker's own maintenance out of it.
Sources
Each source was read on 12 October 2026. Quotes are the source's own words.