Fog Horn Sound

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craigr80

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I just bought a 3 story townhouse in Seattle WA. The house was built in 2007-2008. The house has hydronic heating and a 50 gallon natural gas hot water heater. There is also a thermal expansion tank on top of the hot water heater and what I think is a "temper" valve which mixes cold water and hot water for fixtures other than the dish/cloths washers.

Every time you turn on the water you hear a "Fog Horn" like sound coming from the hot water heater/thermal expansion tank. The sound happens with literally anything that allows water to flow in the house. Hot water, cold water, the dish washer, the water dispenser in the refrigerator...everything. I can make the noise happen by lifting the pressure relief valve on the hot water heater. The noise appears to be resonating or coming from the thermal expansion tank. The noise doesn't happen when I turn the main water to the house off. It also does not happen when I turn the valve allowing water into the hot water tank which is upstream from the thermal expansion tank. So, the sound doesn't happen when I close the water supply to the hot water tank, run the hot water (which reduces the water pressure in the hot water tank) and then run the cold water. This is the only way I can make the sound go away, but my wife doesn't like taking cold showers.

I saw many posts related to toilet fill valves, etc. I systematically flushed the entire water system in my house and closed off each water fixture I could control...one by one to see if the issue was related to a specific toilet or sink.

I measured the water pressure in the house to be ~60 PSI. It drops 5-10 PSI when I turn on multiple water fixtures in the house. I believe this suggests the PRV is working alright. Although I do note an initial spike on the pressure gauge when I first turn the water on. It is consistently 100 PSI and then quickly settles to 60 PSI.

The fog horn sound does not happen when I run the hydronic heating system and water is flowing in those pipes. Does anyone have an idea what this might be and how I can make it stop???

Thank You

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johnjh2o

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Sounds like the pressure reducing vaslve. If the pressure is spiking the reducing valve isn't functioning the way it should.
 

Mr_David

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Try removing the expansion tank. Just need to turn of the water . release any pressure in the system and remove the tank . plug off the fitting and turn water back on. If the noise stopped replace the tank. If not I would start by replacing the PRV. Squealing PRV's are often from the neoprene main washer being loose and vibrating as the water passes by it.

You said you already checked your toilets but thought I would add this link to my video anyway.

Hummer
 
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craigr80

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So...I removed the thermal expansion tank and replaced it with a plug. I did not hear the sound anymore. I installed a new thermal expansion tank and hear the same sound. I guess the sound is happening someplace else and resonating in the thermal expansion tank?
 

craigr80

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I checked the house water pressure again with the thermal expansion tank off and just a plug. The pressure is 80 PSI and then drops to ~58PSI when a single fixture is turned on...I guess this indicates the PRV is bad. Can I change that out or should I ask a plumber to do the job?
 
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