Doing my 2nd annual water heater maintenance with the objective to flush out the entire electric tank. I expected a gradual reduction of sediment from the start to the end (completely empty tank).

Instead it was about 8 oz (~250ml) worth of rusty-colored sediment and then the water was completely clear. For additional context, last year's maintenance involved completely emptying the water heater and changing the anode rod.

I don't mean to overthink this situation but I don't want to assume everything is fine. Which leads me to the question:

When flushing a water heater, is the objective to completely clean out all of the water in the tank or just enough to remove sediment?

If it's the latter, then I assume my particular tank may not require annual flushes. Please let me know what you all think.

  • 1
    I was told by an installer, you should open the drain valve once a month and drain some water out(1/2 to 1 gallon). An annual flush might mean to mixup/stir the water to loosen struck on sediment.
    – crip659
    Commented Feb 2, 2022 at 22:07
  • It also depends on the water. If you have hard water would expect much more sediment than if you have soft water.
    – crip659
    Commented Jul 31, 2022 at 11:04

1 Answer 1


The sediment will be at the bottom. So you will get nearly all the sediment during the first gallon or two while draining. There is generally little to gain by fully draining the tank.


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