Foghorn Sound and Pressure Issue

[Mark629]

Hello,
My house was built in 1992 and I have lived here since 2015. Since then we have replaced all of the toilets (3) and recently added a bathroom to the basement. For about a month now everytime you flush any of the toilets there's a 2-5 second foghorn sound coming from somewhere in the walls. It seems to happen when the water hasn't been used in about a 30 minutes. Ive searched the forum and google about it which mostly states its a fill valve in the toilet but this happens when any of the toilets are flushed.

Also, when using the faucet the water has a higher boost of pressure and slows down after a couple seconds however there is no noise there. The PRV was replaced 3 years ago and Ive tested the pressure with a gauge which read at about 70-75. I am thinking it may be the lack of an expansion tank on my water heater but thought id ask the pros opinions first.

Thanks

 

[WorthFlorida]

Yes, typically an old ballcock flush valve could vibrate. I'm not sure on this and an expansion tank could help. Since you stated about 30 minute time frame, if you're using heated water, the cold water entering the tank will expand increasing pressure but at 70 psi, things should not make noise.

Vibrations usually will come from anything with a diaphragm or a washer at the end of the valve stem. When the condition is right, place your hand on the PRV and have someone flush a toilet. When a toilet is flushed, the flush valve is nearly wide open cause a big rush of water. You might be able to do it with using a garden hose. See if you feel the vibration on the PRV. Also you can slowly open a faucet to drop the pressure then flush a toilet. It will definitely indicate that it's the higher pressure causing the noise, But what? Since the PRV is common to everything, possibly it's the PRV.

 

[Sponsor]

 

[Mark629]

Thanks for your reply,
I have opened a faucet to let out the pressure then flushed and there was no sound. Previously Ive tried flushing and standing by the PRV to see if the sound was coming from it but it was not. I will try your suggestion and put my hand on it while flushing. I hope its not the PRV, I replaced it a few years ago and it was a pain in the a$$.

On a side note my main shut off has a slow leak that is on the list to be replaced. I figure Ill replace that when I put the expansion tank in and maybe adding a PRV to that list. UGH!

 

[John Gayewski]

Try turning the PRV down. You don't need that much pressure unless you're living in a mansion with a mile of pipe in it.

 

[Mark629]

Good call John, thanks!
I turned the pressure down to around 55 and the noise is gone now. Its funny because those are supposed to be factory set to 50 correct?

There's still a boost of pressure when the faucet is turned on after being off for awhile and slows down 2-3 seconds later. I'm going to figure that is because of my lack of an expansion tank which will be installed very soon.