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

[DIYNotIan]

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

 

[cross thread]

It will as less restrictive but a lot of will depend on length of run and head water ,can you not run a tank feed cold ?

 

[DIYNotIan]

It will as less restrictive but a lot of will depend on length of run and head water ,can you not run a tank feed cold ?

Hi there

We did consider taking a cold feed from the loft tank, but decided to use the equalising valve in the end, for a few reasons.

The head of water is around 2.5m. Not great, I know. And the length of pipe run from the cylinder to the bath hot tap is around 5.5m.

I think based on what I've learnt that 22mm might be useful, so think I'll go with that. One thing I didn't consider though is the shower hose itself, so will be looking for a wide bore hose.

Cheers

 

[jeff the gasman]

Fit a universal pump to the hot prior to the PEV and you’ll get a fantastic shower.

 

[ETAF]

Note , I'm not a plumber, but recently re-did my bathroom and looked into all this -
Bungalow - so not a good head of water, Small hot water Cylinder which has a cold water tank section at the top.
Shower part of the mixer tap - this type of thing, https://www.mrcentralheating.co.uk/...zPsFwllhtB740g79QR6NWSbuPpkxHk5xoCTsoQAvD_BwE
BUT i took off the cradle and fitted a shower rail for the head.

I made sure we had 22mm full run from cylinder to the hot water TAP (previously for some reason it had a small section of 15mm ???) I also made sure the isolating TAPS were full bore, as we had a tap from the cylinder to isolate ALL the hotwater - one for the bathroom, to isolate the bathroom hotwater and the En-suite hot water , and then one to the TAP itself - a bit overkill, but i have been flooded out in previous houses before ....

I purchased wider bore hose - 11mm from screwfix
I fitted a pressure reducing valve (again screwfix) just onto the cold to balance
Bath / mixer TAPS where low pressure - old fashioned type with an old fashioned washer

Shower works great, or least its fine for me to have a shower each morning.

I looked at various pumps and discussed with manufacturers - our cylinder was to small for a pump and they all recommended changing , i also understand in some areas , if you fit a shower pump, you are supposed to inform the water company , and they fit a meter.
Also had varios plumbers quote for refitting the bathroom, and most wanted to change the cylinder.