My water pressure left me today in my time of need and brought to my attention a question. Why do I lose hot water when I lose water pressure? Is my water heater not full of water like I always assumed it was? I had hot water the second the pressure came back. Why no hot water? All I needed to do was wash my hands, but no.
Your tank was I’m sure full of hot water. But if the tank has no pressure in the cold water pipe on the input side, the hot water is not pushed out of the tank and to your faucet.
If the faucet was at a lower level than the tank it might be possible for hot water to flow to the faucet but not to any great extent as the water in the tank must be replaced by either cold water or air. If you get too much air in the tank you could burn out a heating element if the heater is electric.
The Cold water that feeds the water heater is responsible for pushing the heated water out of the heater, through your plumbing, and out of your faucet. It replaces the hot water in your tank with cold water, which must now be heated. It doesn’t come off the street hot, you know.
Thus, when you have no street water pressure with which to purge the tank, you have no hot water coming from your faucets. Your heater was indeed full of hot water, but it had no means of getting to you, save for the drain valve at the bottom.
I can’t believe people are asking this type of question.
Is it really that hard to figure this out?