Farting PRV

[Tom]

Hi all, for a little while now there has been a noise coming from the plant room that lasts for a few seconds when the bath filler is opened. It sort of sounds like a grinding/vibrating/fart. I managed to track the source down, and I think it's coming from the PRV.

Is this a known issue with PRVs? Seems like you can replace the cartridge, or perhaps take it out and give it a clean.

I have a video of the thing making the noise but the file is too large to upload, even after resizing. Any ways around this?

Cheers

[stevenlee]

Yes, very common, that is the PRV chattering when the bath filler calls for full flow. Stripping it out and cleaning the seat and cartridge can quiet it down for a while, but if it is a few years old I would just fit a new cartridge, they are cheap and it is usually the permanent fix. For the video, uploading it as unlisted on YouTube and pasting the link works fine on here, or you can convert a short clip to a GIF.

[ToughButterCup]

My PRV is known as Silent-But-Deadly in our house.

[Tom]

On 16/10/2026 at 09:34, ToughButterCup said:

My PRV is known as Silent-But-Deadly in our house.

Thanks, I'd suggest you clean your cartridge.

 

Just so l'm clear before I start waving the spanners around, is it the grey thing that I need to unscrew to get at the cartridge?

[Nickfromwales]

23 hours ago, Tom said:

Thanks, I'd suggest you clean your cartridge.

 

Just so l'm clear before I start waving the spanners around, is it the grey thing that I need to unscrew to get at the cartridge?

Yes.

 

I’m not sure how much success this will yield, but worth starting the process of elimination here.

 

Is the rising cold main in that room with the obligatory double check valve? Crud in that is usually a culprit too, as it audibly moans and groans when unhappy.

 

Double check the pre charge pressure in the white expansion tank as that is often installed without a proper commissioning ever taking place.

[SimonD]

On 15/10/2026 at 12:13, Tom said:

grinding/vibrating/fart.

Always quite difficult to diagnose sound by description. Could be the inlet group or the expansion vessel. Here is a video of a failed expansion vessels at its worst (customer left it a long time to ask me to check it out) making similar noise. This was a warranty replacement on an installation I did (and before anyone comments on the lack of pipe insulation, the customer specifically asked for me to do this to provide warmth to their airing cupboard as I'd removed a small rad when stripping out the old combi boiler). Vessel was installed with correct pre-charge at 3 bar and I'd re-checked pre-charge pressure when looking at the fault, so for all intents and purposes it looked like the expansion vessel was okay.