Hoping someone can help me with this weird issue I am having with the water pressure at my house (at least seems weird and mysterious to me). This is an issue that started happening about 6 months ago.
When we turn a faucet on, hot or cold, we get a burst of higher pressure water for a few seconds and then it settles down. We have a pressure regulator on the main water line coming into the house and it seems to be working because I have adjusted the value to reduce the pressure some.
About 6 months ago, I replaced the pressure relief value on the water heater because it was constantly allowing hot water to drain. After a few weeks it started leaking again. It was about this time that we noticed that we get the burst of higher pressure water when we open a faucet.
If we turn off the cold water intake for the water heater, we don't get the pressure spike when we turn on a faucet. So the pressure issue is apparently related to the water heater. I have checked and the water heater is set to around 125 degrees and the water that comes out of the tap is around that temp so it isn't set at too high of a temp.
Now, the mystery is this. As a test, I turned off the power to the water heater and ran the hot water until what was coming out was barely warm so that there would be no extra pressure in the system due to hot water expansion. After doing this, I still get a spike of higher water pressure when I opened a faucet.
So, when the water to the water heater is turned off, I don't get a spike of water pressure when I open a faucet. When the water to the water heater is turned on, I get a spike in pressure, regardless of the temp of the water in the heater and if the power is even turned on to it.
I know I need to install an expansion tank and replace the water heater pressure relief value, but I don't want to spend money if that isn't likely to fix the issue because of something else that may be going on. Any suggestions on what may be causing this issue and would an expansion tank really fix the pressure issue?