Is 22mm pipe worth it when using a 15mm pressure equalising valve?

[Plumb Line]

Hi all

Making some final decisions on the plumbing for our bathroom refit. Background: we'll be having a shower mixer tap on the bath, hot water is gravity fed, and cold is mains. So I'll be having a pressure equalising valve (PEV) before the shower mixer to balance the hot and cold. I know the shower power will be pitiful, and am happy with that.

But I don't want it to be any more pitiful than it has to be! So...

If the pipework from the cylinder to the PEV, and from the PEV to the tap, were all 22mm - would that perform better than 15mm pipes? I ask because the connectionson the PEV are all 15mm, and I don't know if it's a case of "the weakest link in the chain, as it is with so many of these things. Logic suggests to me that 22mm pipework would still be helpful. But I'm an armchair plumber, so it's over to you guys.

Cheers

 

[Ric2013]

Provided the flow that your mixer allows is sufficient that there would be a drop in the working pressure of the hot water entering the equalising valve (i.e. the pressure measured with the shower flowing) which, site unseen I'm guessing will be the case, then 22 will perform better than 15 even though it goes through a 15mm valve.

 

[Plumb Line]

Great, thanks for confirming @Ric2013

Think I'll definitely specify 22mm for the job in that case.

Cheers

 

[Timmy D]

Off topic but don’t fancy pumping the hot?

 

[Plumb Line]

Off topic but don’t fancy pumping the hot?

No. We prefer to use as little water and energy as possible, so are happy with a weak shower! So long as it works. Thanks for the suggestion though.

 

[Last Plumber]

No. We prefer to use as little water and energy as possible, so are happy with a weak shower! So long as it works. Thanks for the suggestion though.

Is the tank not big enough to run a cold feed to the mixer and lose the pressure valve?

 

[Plumb Line]

Is the tank not big enough to run a cold feed to the mixer and lose the pressure valve?

I think it is; it's a 50 gallon if memory serves. I'd need to nip up into the loft to double check.

We have considered a cold tank feed as an option. Not sure what would be the most expensive route... The tank is more or else above the bathroom, so it's in a good position. But the internal walls are solid and so the pipe would need to be chased in.

On top of that, when the boiler dies (hopefully not for a long time but you never know), we'll likely go for a new system entirely, and if we do that the loft tanks will become redundant. That would then mean having to replumb the cold to the bath. With the PEV, I'm pretty sure that could stay and so nothing would need to be done at that end. So it seems The PEV is the more future-proof option. If the cold feed was significantly less money, then maybe. But if not, then I think the PEV is the way forward.

Many thanks for the reply and for sharing your thoughts.

 

[Timmy D]

I think it is; it's a 50 gallon if memory serves. I'd need to nip up into the loft to double check.

We have considered a cold tank feed as an option. Not sure what would be the most expensive route... The tank is more or else above the bathroom, so it's in a good position. But the internal walls are solid and so the pipe would need to be chased in.

On top of that, when the boiler dies (hopefully not for a long time but you never know), we'll likely go for a new system entirely, and if we do that the loft tanks will become redundant. That would then mean having to replumb the cold to the bath. With the PEV, I'm pretty sure that could stay and so nothing would need to be done at that end. So it seems The PEV is the more future-proof option. If the cold feed was significantly less money, then maybe. But if not, then I think the PEV is the way forward.

Many thanks for the reply and for sharing your thoughts.

Just putting it out there so you’re aware. If you ran a new pipe from the tank, when you changed boiler. You could just connect the tank mains water fill line to the outlet to convert the supply. No need to mess around in the bathroom.

 

[Plumb Line]

Fair point... Also, I'll be making the bath panel in such a way that it is removable. So access wouldn't be an issue anyway. And on top of that, the cold water main actually comes into the bathroom underneath the bath where the taps are. So it's not far away even if the change was to be made under the bath.

Hmmm... Perhaps another thread is in order weighing up which is the best of the two options...

Thanks for the help - much appreciated.