Why does dirty water come out of the pipes after the main water to the house has been turned off for a while and then turned back on?

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More detailed question: Why is it that the water stays clean inside the pipes when the main water to the house is turned on, even if we don’t use the water for a while, but gets dirty if we turn off the main water valve and turn it back on later?

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2 Answers

Anonymous 0 Comments

This is also why you shouldn’t cook (food/coffee/etc) with hot water from the tap. Hot water has been sitting in a hot water heater and can transfer its sediment.

Anonymous 0 Comments

Time. When the water is turned off, what water is left in the pipes is allowed to settle. All water over time will go back and start to smell as bacteria build up.

The water will be fine for a short while, so if you’re not using it for a while you will be fine. But the longer you leave it, the more likely the water will be bad.