Bath/shower mixer - manual

[ag17]

Hi, I'm looking for some advice regarding a bath/shower mixer. My daughter has just moved into a two storey house with a bath/shower mixer in the first floor bathroom which is not mixing - it's either all cold or all hot, so no mixing. The hot is gravity fed, so pressure is about 0.2 bar at the mixer; the cold is mains fed, pressure measured at 3 bar on the ground floor.

I think the lack of mixing is due to the pressure difference between hot & cold. I thought installing a pressure reducing on the cold feed should solve the problem. All the common pressure reducing valves I have seen, however, have a minimum output pressure of 1 bar, so it won't be possible to have the hot & cold perfectly balanced.

Do you think reducing the cold to 1 bar with a pressure reducing valve will work? Any other suggestions gratefully received! Many thanks. Andy

 

[Madrab]

The hot is gravity fed, so pressure is about 0.2 bar at the mixer; the cold is mains fed,

Should never have been fitted that way, would always struggle to work properly.

To get it working properly with gravity HW, then the shower should really be pumped and both hot and cold should be gravity fed. It can sometime work by pumping just the hot and reducing the cold mains to bring them closer to being balanced but TBH it's a bit of a fudge and invariably they all eventually cause issues due to the imbalance.

 

[ag17]

Many thanks for your reply Madrab. Accessing gravity fed cold to pump doesn't seem to be possible as the system uses a combined tank like the ElsonFlow Opal.

What do you think using a pressure equalising valve (e.g. https://www.bes.co.uk/water-pressure-equalising-valve-16711/) on the feeds to the manual mixer unit, with or without pumping the hot?

 

[Madrab]

the system uses a combined tank

Ah, OK, yep a combination cylinder makes things more complicated.

A pressure balancing/equalising valves would work but they work by dropping the higher pressure down to the level of the lowest pressure, therefore if the HW pressure is very low the resulting cold and therefore shower pressure will also be very low. There used to be a venturi shower option whereby the hot was drawn through the shower by the pressure of the cold, a Trevi Boost was one such option, don't think they are available now.

Using a pump to increase the HW up to around 1 bar and then drop the cold pressure via a pressure reducing valve is one option, as suggested though it's not fool proof and can suffer from issues due to the cold pressure inhibiting the HW flow to allow the the pump to start.

Another alternative could be to convert the HW to unvented, if the cold mains pressure and flow is suitable, therefore the supplies would both be at mains pressure. If the mains could support it, this would be the best long term solution IMO.

 

[ag17]

Currently flow at the shower head with just the hot tap on is adequate - not brilliant, but adequate. So we're going to install a pressure equalising valve and see how that works. We then might move to pumping the hot to improve things. Will let you know how we get on.



Converting to unvented would be ideal, but daughter doesn't currently have the budget for that!

 

[gary plumb]

Maybe a Trevi boost would work if they still make them.

 

[gary plumb]

Sorry just realised yours is a deck mounted shower

 

[ag17]

Just to close the loop... we fitted a pressure equalising valve and it has made a huge difference - the shower temperature is now very easy to control. Flow/pressure is, of course, low (as expected), but at least the shower is usable.