Pulsating Pipe Nightmare - Bad PRV?

Well .. turns out my plumber didn't adjust the PRV from the factory settings of 45PSI. thats why I didn't have the immediate problem again. I checked my pressure and set it back to 60 and I have all the same problems. So..2nd PRV same problem.. I guess its not the PRV. I could cry lol!! So trouble shooters: This is what I have done to try to pinpoint the problem and location.
While the sound is occuring-
Closing the Ball Valve shutoff on Backflow Febco65(outside near hosebib and sprinkler manifold box)= no effect
Turning Gate Valve Below PRV = No Effect.
Closing the Ball Valve shutoff on irrigation-T in basement = stops the sound (only if the sound is happening when the sprinklers are running)
Closing the Ball Valve shut off on the cold water to waterheater changes the sound of the chattering, but doesn't stop it. (no thermal expansion tank installed) ; this is 30-40 ft away.. any explanation?
All Toilets are QuickFill/Not BallCock / All Anglestops have been replaced.
Also FYI this intense hammering doesn't immediately start on the sprinklers (this house i bought has 8 zones..yes 8 don't know why they installed it that way. The timer is programmed to run 2x in the am per zone. It can run through all 8 zones fine the first cycle, then... zone#6 kicks in on the 2nd cycle and BAM... the hammering starts.
This is not only a sprinkler issue; as it happens when the sprinklers are off and I flush any of my quick fill toilets and they are in the "filling mode"

Thanks for your help...

First off you need an expansion tank on the cold water side of the water heater because the PRV has made your water distribution system a closed loop (thermal expansion has no where to go). Other than that, your issue could be a #6 zone valve solenoid.

LiQuId said:

Yowza, that is a hell of a Sound to be made from a Wc...

I have not yet encountered this but Will be sure to remember that video....

So, What was the solution Mr David??

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Sorry I was a little slow on a reply. I just stumble back into this thread. Just replace the old ballcock with a Fluidmaster 400a or better yet a Pro45B

I'll take another crack at this.
Are you sure the valve below the meter is a Gate. It might be a globe valve. They look similar.
The globe valve has a neoprene disc and if it's loose that is a common cause of the noise you have.
Can you turn off the supply to the valve so you can take it apart . I'd replace it with a ball valve. use a quality BV though.

I agree with hyper48fan. You need an expansion tank. It may or may not resolve the humming noise but until we get the pressure under control and in a normal range, this is hard to diagnose. Understand that without an expansion tank, when someone uses a significant amount of hot water (like when taking a shower), the water heater gets re-filled with cold water at approximately 60psi. As that water is heated, the psi will rise because the PRV does not allow the water to expand. It is not uncommon for it to go as high as 150psi and start tripping the relief valve on the water heater. At these high pressures, all kinds of weird things can happen. All that pressure pushing back from the house side of the PRV can't be good. You also mentioned the water heater shut off changes the sound of the chattering... some water heaters have heat traps installed and it causes chattering.

Mr_David said:

Sorry I was a little slow on a reply. I just stumble back into this thread. Just replace the old ballcock with a Fluidmaster 400a or better yet a Pro45B

Click to expand...

I,see so basically Install quality parts