If I let my pressure tank stay empty for while (usually the result of flushing the toilet a couple times during a power outage), when the power comes back on the water is discolored for a while (30 seconds to a minute).

Can anybody tell what the discoloration is or where it comes from? enter image description here

If I run the hose connected to the inlet/outlet of the pressure tank, the water runs clear, so the discoloration doesn't appear to be coming from outside.

  • 2
    corrosion would do that (inside the tank)
    – Traveler
    Commented Jan 4, 2023 at 18:51
  • 1
    Will need to have it tested to get the answer of what it is. Sediment/dirt(earth)/rust are probably the main options.
    – crip659
    Commented Jan 4, 2023 at 18:55

1 Answer 1


Pressure tanks can trap some dirt, rust, and other gunk that is in your water supply. Generally you don't see this as it's settled to the bottom of your tank or is held in place with some "slime" that can form in there.

When you let the tank get completely empty, however, this stuff can be loosened and then can get pushed out in the first few gallons after you refill it.

I'd flush the lines for a while and it should clear up after 10-15 minutes or so.

  • Isn't the outlet at the bottom of the tank? If so, does that mean that the junk in my case is being trapped in the "slime"?
    – Zack
    Commented Jan 4, 2023 at 23:54
  • 1
    If you open up an old tank you will see that the inside is coated with a somewhat sticky "slime". That holds debris but the fully expanded bladder will dislodge some of that and it will get pushed out into your pipes.
    – jwh20
    Commented Jan 5, 2023 at 1:07

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