Pressure reducing valve / unvented

[BN9Pete]

I have an indirect Megaflow in my house, there is a 22mm pressure reducing valve in the cylinder cupboard on the supply to the Megaflow as expected.
I also have another 22mm pressure reducing valve above the mains stoptap in my utility room.

My house is about 15 years old and the Megaflow and valves were fitted when the house was built.

Hopefully this doesn't sound like a silly question, but why two pressure reducing valves?

The flow from my hot taps has got slower in the last couple of days, would this be a problem with one of the PRV s?

I did the unvented HW course about 20 years ago and I know my ticket is now not valid and apart from installing unvented cylinders on sites over 12 years back I haven't got involved with unvented.

Any advice appreciated, thank you.

 

[Ch4 plumbing]

They may not have run all the colds from the balanced cold at the cylinder.

 

[Ch4 plumbing]

I would clean the filters on both pressure reducing valves.

 

[BN9Pete]

They may not have run all the colds from the balanced cold at the cylinder.

You are correct, after the pressure reducing valve next to the cylinder, the main only feeds the cylinder and the cold to a mixer shower.

 

[Ch4 plumbing]

It happens sometimes, It's a mistake made by the initial installer shouldn't happen though.

 

[Best]

As you know, you are supposed to have unvented units all serviced once a year for safety and to keep warranty (often 25yrs on cylinder).
On a service, or at least on some of the services the filters would need cleaned on any pressure reducing valve.
Get your G3 qualification as it is worth it IMO, so you can service & install.

 

[SimonG]

I would say its good practise if not able to utilise balanced cold. To fit prv after stop tap. Ensures balanced supplies without ripping house to bits.

 

[BN9Pete]

Thanks for the replies, I'm seeing things a bit clearer now.
After reading the replies I realise about the balanced supplies, it was probably easy to fit 2 pressure reducing valves during installation.

I was wondering why the installers could have just fitted 1 PRV above the mains stoptap, but I'm sure the older Megaflow also came with a PRV and combined fitting in the box that had a tee for balanced cold and Expansion relief valve.
( cold water combination valve)

I think the PRV above the incoming main stoptap must be fine as the pressure at all cold taps and toilet cisterns is good.
It's only the hot water outlets that are a little slower.

 

[townfanjon]

A lot of new ish , new builds fitted PRV 's as just normal build spec. Before cylinders and boilers even went in.

 

[BN9Pete]

A lot of new ish , new builds fitted PRV 's as just normal build spec. Before cylinders and boilers even went in.

Probably a good idea with a 22mm brand new main.