I have a gas hot water heater in my basement. It looks as though
black water shot out of the pressure relief tube. There is a large
splat mark on the floor of dried black residue. The splat is about 6
feet in diameter.
I tested the relief valve...clear water came out.
Otherwise, my hot water has been fine and the water clear.
The only factor i can think of is that i left the house vacant for a
week. During that time i shut off the cold water supply from the
Does anyone have any thoughts on this?
Shutting off the water supply may have caused the problem by creating a
closed system so that when the water heater came on the expanding water
had no place to go other than out the overpressure relief valve.
That's if you don't have an expansion tank in the system of course.
You're on to something.
On a very slightly related moment, a friend of mine had the power off, at a
house he was trying to sell. Winter, cold. I suggested to drain the pipes,
which we did. Find out later, he'd closed the toilet valve, and the water
split the (copper) tube from the shut off to the tank valve.
I went and bought a nylon braided tube, and put the plumbing back in action.
If I remember correctly, hydrogen gas can build up in a water heater.
The metal of the anode rod reacts with the water producing the gas.
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