Pressure reducing valve - can I remove?

[Mjward]

As part of full house renovation, I've switched from a conventional boiler/gravity fed tank to a combi boiler. Under the old system I note that a pressure reducing valve has been fitted to the pipework feeding the shower mixer (assuming as mains cold overpowering the supply pressure from the hot).

Given I'm now on a combi system, is this pressure reducing valve redundant/can I remove it?

 

[Ben-gee]

Yes I agree with your logic and I would remove it.

 

[Last Plumber]

Yes, it sounds like the right move.

 

[Mjward]

Thanks both, will get rid

 

[John.g]

Did you have a thermostatic mixer on that shower and was the shower installed upstairs?, just wondering if anything special about that PRV as very low pressure cold outlet required for shower upstairs in view of very low hot water head.

 

[Mjward]

Did you have a thermostatic mixer on that shower and was the shower installed upstairs?, just wondering if anything special about that PRV as very low pressure cold outlet required for shower upstairs in view of very low hot water head.

Yes to both and was only preceding pipework to shower

 

[Ben-gee]

John , he’s switched to a combi.

 

[Mjward]

Also not sure how clear it is from pic but HW feed was originally in 22mm from the boiler. My intention was to replace all pipework in this bathroom with 15mm unless recommended otherwise?

My thinking being is that at 22mm there is more cold water sat in pipe needed to be pushed through although maybe it's needed to get higher HW flow rates from boiler Vs 15mm?

 

[John.g]

John , he’s switched to a combi.

Yes, aware of that but always wondered what is the maximum differential pressure between cold/hot that a thermostatic mixer will still control at, 1bar or so??

 

[Ben-gee]

I think there was a trevi that did 5:1, but most ask for nominally equal pressures. The problem occurs when the supply with lower pressure (usually hot) is too low in and of itself - the solution is usually to pump the hot up to a higher pressure, not necessarily to match the cold.

There also used to be a couple of Venturi showers where the cold main drew the hot in at a greater flow than it could manage on its own, don’t know if they’re still available, I used to have two on my patch and they worked well. One now ‘updated’ to combi, the other unvented so I don’t see them anymore.