Banging pipes- when faucets, shower, dishwasher, and washing machine used

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  #1  
Old 09-20-16, 10:04 AM
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Banging pipes- when faucets, shower, dishwasher, and washing machine used

Hi All:

I recently returned home from being away for a month to find that our once quiet pipes are noisy. I checked the thermal expansion tank and water came out of the air valve. I replaced the tank, inflated to 63psi, and turned the water back on. The pipes were quiet for a day, but the noise has returned.

Here are some potentially useful facts.

1. The plumbing in the house was completely replaced in 2003, and had been noise free until recently. The supply side is copper and secured to the bottom of the floor joists with copper clips.
2. Using a Rain Bird pressure gauge on an outside hose bib, the pressure in the system is 63 psi.
3. The thermal expansion tank is 2 gallon and air charged to 63psi.
4. The house has a tankless hot water heater, so there is no hot water unless water is flowing.
5. Pipes are noisy if dishwasher and washing machine are drawing water. Toilets, showers, and sink make noise to a lesser extent.
6. Noise is like water hammer.

Could my pressure regulating valve be going bad? Is my house haunted?

What steps should I take?

I appreciate everyone's assistance.
 
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  #2  
Old 09-20-16, 04:07 PM
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If you charged the tank to 63psi when it was empty and your water pressure is 63psi then no water will enter the tank. Water will only enter the tank when the water pressure is higher than the air pressure so tanks are usually pressurized to something less than your water pressure.

As for the PRV going bad. What pressure do you want? Is the valve able to be adjusted to that pressure? Often when PRVs fail you will have reduced water volume.
 
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Old 09-20-16, 04:52 PM
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Pilot Dane:

Thank you for chiming in.

I see your point about the pressure. The expansion tank instructions said to equalize the water and the air pressure. However, I will crawl under the house tomorrow morning and let 10 psi out and see if that helps.

The water pressure and volume has been fine since we did the remodel. The only problem now is that banging and vibrating sound that is made when the water is running through the pipes. If I can get it quiet again, I will be satisfied.
 
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Old 09-21-16, 07:10 AM
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When a pressure tank is used with a water pump it's common to set the tank pressure 2-3 psi below the lowest system pressure. That insures that the water is always pushing up into the tank to some degree even when the system is at it's lowest pressure. When your water pressure rises the air gets compressed and more water enters the tank. If you don't know how much your water pressure varies throughout the day setting the correct pressure may take some trial and error.
 
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Old 10-18-16, 05:12 PM
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Bottom line, a 55.00 PRV rebuild kit solved the problem.

Okay, here is the rest of the story. I lowered the pressure in the tank a few pounds but still had the banging. I was thinking about replacing the PRV. I bought one and crawled und the house. After looking at the installation, replacing it was over my head and would require a real plumber. So, I took the PRV apart and flushed it out. I lubricated it and put it back together. The hammer stopped but restarted. I ordered a 55.00 rebuild kit from Amazon for the PRV and installed it. While flushing it this time, I reached in and found two chewed up washers in the bottom of the valve. While I do not know if that was causing the noise, the problem has been solved.

Thank you for your help.
 
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