Is this water hammer?

elkridger · Aug 23, 2009, 06:21 AM

I have had this knocking pipe problem for a couple of months, please help.

I have read a lot about the water hammer phenomenon since this pipe noise problem started bothering us. Unlike most of the stories I read, our problem doesn't seem to be associated with any specific faucet. It typically happens in the night when nobody is using water in our house. It sounds like the pressure is building up and gets real loud after a while. If I open a faucet (any faucet) and let the water run for a moment, the noise would go away. Kinda feel like the air (if it was air) was released by turning on a faucet. But later it will come back again.

I had thought this might be related to a false pressure reduction valve thus the water pressure was too high in our house. But I tried to adjust the valve (turning the screw counter clockwise) and it did decrease the water pressure (water runs at a much lower volume). So I think the valve works fine. I also tried to shut off the main water valve and drained all water for the house as other people suggested. Didn't work either.

Now I am running out of options. Could anybody help me please? Thanks.

elkridger · Aug 24, 2009, 12:23 PM

I don't know how the air gets in there. I think it has some to do with the pressure? Even if there had been some air in the system, I already tried to drain out all the water. Another clue is, the noise started after we came back from a one week vacation. Before we left for vacation I turned the water heater's temperature setting to vacation. I don't know if that has some to do with this problem.

I didn't notice any water related work in my neighborhood.

Quote:

Originally Posted by speedball1

Tell me more about the air in your lines. Has the city been doing any work on the main? Call the Building Department and ask and then let me know. Tom

elkridger · Aug 25, 2009, 09:26 AM

Yes. This had been the original culprit I thought of. Initially I adjusted the screw to see if the water pressure actually decreases and it did. So I thought that meant the PRV was OK (wrong conclusion here). Last night I bought a pressure gauge back and found out the pressure was over 100psi and would not drop even when I turned the screw all the way out (the upstairs shower still lost water volume ). So this morning I bought a new PRV and replaced the old one. Now the noise is gone. I think the problem has been resolved.

Thank you very much for your inputs.

Quote:

Originally Posted by speedball1

Is there a PRV, pressure reducing valve, next to where the water enters your house? Let me know. Tom