Pressure Reducing Valve

[WhitbyLad]

Hi Guys,

I moved in to a new house, and the pipes banged within the walls when the downstairs toilet stopped filling.

The plumber who came to investigate said the reason was because there was no pressure reducing valve installed, so installed one, set to 1 bar.

The pipe banging has been eliminated, but now the flow out the taps is poor, the toilets take ages to fill, and if the shower is in use, and a toilet is flushed, it goes red hot (electric shower) as the flow through it is reduced while the toilet is filling. None of this was a problem prior to the PRV being installed.

The PRV isn’t easily adjustable, and you need to remove the grey cap where the spring is situated, and screw the section internally of the cap which houses the spring.
There is no accuracy though, as when screwing the cap back on, the internal screw section can easily spin.

The PRV is a RBM brand, 22mm like this https://www.manomano.co.uk/catalogu...nox-et-filtre-3-4-rbm-france-28480500-4825402


Can the grey section be replaced for an adjustable one, so I can adjust it easily, as currently I need to isolated the main incoming valve, drain the pipes and “adjust” the pressure, but it’s hard to get any accuracy. It’s currently at 3 bar and the pipes are banging again, so I need to lower it.




Thanks a lot

 

[WhitbyLad]

Actually, is that type adjustable a different way which I’m not sure about? There is only a hole in the grey cap, no screw or anything.

it does have a pressure gauge on by the way.

 

[Madrab]

Your plumber is a bit of a muppet.

It's not the pressure that's at fault though it is what's creating the knock, it's actually the pipes moving when the valve shuts, typically know as hammer. Basically the pipes are either touching each other or they aren't fixed properly.

Some PRV's use an allen key, others where the cap unscrews and there's a screw/turn head underneath. You should have the installation info that came with the valve? Or call the plumber and ask him?

 

[denso13]

Or a problem with the fill valve if it only did it when that was used.

 

[WhitbyLad]

Your plumber is a bit of a muppet.

It's not the pressure that's at fault though it is what's creating the knock, it's actually the pipes moving when the valve shuts, typically know as hammer. Basically the pipes are either touching each other or they aren't fixed properly.

Some PRV's use an allen key, others where the cap unscrews and there's a screw/turn head underneath. You should have the installation info that came with the valve? Or call the plumber and ask him?

Its a new Barratt house. I did report the fault as the pipes, but the plumbers came when I wasn’t in, and my wife didn’t get involved.

He installed that PRV as he said it should have one on. But set at 1 bar, the pressure isn’t good enough upstairs.

To remove the grey cap, I have to turn the water off and drain the pipes to remove it, and there is a turn head, which compresses the spring more. But it’s hard to get an accurate pressure as you have to adjust it with the water off and blindly turn the adjustment.


What is the max pressure I should aim for?

Can you change the cap for one with some external adjustability on?



thanks a lot

 

[WhitbyLad]

Or a problem with the fill valve if it only did it when that was used.

Sorry it does do it when the washing machine is on too, which is next to the toilet, so I think that’s off the same feed.

 

[Madrab]

I wouldn't ever set a PRV to 1 bar unless there was an appliance or outlet that specified it. Even then I would probably install the PRV next to the appliance that needed it. A whole house PRV would usually be set to between 2-3bar.

Unfortunately we come back to the situation whereby we really need to know what the system dynamic pressures and flows are. The PRV is adjusted as you specify, under the cap by adjusting the screw (can you take a pic with the cover removed?). I don't understand why you are having to shut off the mains though, you should be able to adjust the pressure live with an outlet or 2 running. If you need to adjust down then close the supply, open an outlet set the pressure down and then open up the supply, have an outlet open slightly as you adjust it back up.

The 2 valves that do close quickly are your WM/DW and toilet inlets. When they close they send a shockwave down the pipe, that then manifests itself as hammer when it finds pipes that are too close together or are sitting on something and aren't clipped properly, they then move and create the hammer (banging) noise.

You won't get a fitting for that valve I don't think but you can replace it with one that has an external adjustment - like the honeywell D05.

 

[hard-work]

What is the static and dynamic (when the taps are on) pressure of the water? Usually it is a matter of installing a small shock arrestor or two or three at the points of the knocking. Or just one large one. If you have mains fed DHW then a pressure reducer may affect performance of showers, baths, etc. Only if the mains pressure is very high, it usually is not a problem. Sometimes jumpers in mains stopcocks can jump up and down, a full bore valve usually solves that.