we have mains cold water and tanked hot (not combi)

we have installed a mixer shower but i think the pressure differential is too great and we are getting water backing up through the hot system into the header tank and overflowing (even with mixer set to hottest setting)

can you get a bar mixer (or any other mixer for that matter) that can deal with high differential pressure or do i need to seperate hot and cold using say a traditional bath/shower mixer tap arrangement?

That sound odd. You shouldn’t have mains water supplying the bath if the hot is gravity fed.

A non-return valve in the hot supply to the valve would sort it, assuming the valve is working as it should, but you will never get even pressure between hot and cold supplies.

Some mixers won’t work with gravity feed hot, or specify the max pressure differential across the two supplies for it to work. It is possible to add a separate electirc pump to the supply feed to equalise this…. but if thta’s the case you might be better off with a power shower, rather than a mixer?

i`m not expectiung to even the pressure i just want to stop water pissing out of the house!

flow rate is not massive but constant. as the rate of flow is not great (think steady trickle) would hte non return valve activate?

can you get fitting to deal with this differential pressure as i’d prefer that ideally?

a mixer shower was fitted previously (but we couldnt re-use it as it had all the dials removed) but it wasnt a bar type. i’d rather not have to remove all the tiling and get the plumber back again. its been a saga to get this far!

an electric power will be the last resort option.

did the plumber recommend/install the setup you’ve currently got?

Sounds like the mixer isn’t suitable for the set-up

Have you got the manual for the shower/can you download it? Does it show that the mixer you have is suitable for your system? I know the Mira manuals show specifically what systems will and won’t work for each shower.

If it’s not right for your system and all the pipework is already behind the tiles….. well, I won’t go any further, other than to suggest getting a plumber in to see what can be done…. Fingers crossed.

i`m kinda resigned to doing something else just blindly hoping someone somewhere made something i could use. from what i can find a shower mixer like a bath filler mixer with twin taps but without hte bath filler bit does not exist.

i think an electric power shower is best long term solution but unfortunatly is also the most expensive.

MF i know the mixer isnt suitable – hence the questions!

MF i know the mixer isnt suitable – hence the questions!

Fair enough – I am being more dim than usual

A power shower is going to be cheaper than a true ‘electric shower’. Should just run off 13amp socket, rather than dedicated cable for a 10+kW electric job. Will be extremely unlikely that the existing pipework lines up with the shower though, unless you run additional pipes to the power shower from the existing mixer pipes poking out of the wall….. would save having to remove tiles etc, but may or may not look like a bodge? Be warned though, power showers can be quite NOISY!!!!!!!

I don’t know anything which will reduce static and dynamic pressure of cold which is the problem. A NRV might block it, but likely as not there won’t be enough head from the loft tank in the hot line to operate a NRV in the forward direction. – By your admission, the reverse static pressure is bigger then the forward, so how will the NRV ever open? Even if it does, you might then get a very measly amount of hot in the mix, and it might not give you a a hot shower. If the cold is flowing back up the hot with the mixer turned off now, I’m fairly surprised you can actually have a hot shower at all.

The only proper way is to reconnect the cold from the loft header tank. Ideally it should have an independent feed from the tank to prevent pressure changes when someone turns on a tap elsewhere.

There is one shower brand I’ve seen that was a cold mains “powered” – effectively a power shower. Can’t recall the brand, but it uses cold mains water pressure as the energy source to pump the hot. The outcome is cold water “waste” at low pressure which you’d need to put into the drain.

would a restrictor in the cold help? Or run the cold tap in the sink while you shower?

run the cold tap in the sink while you shower?

“Turn all the taps on and start the washing machine, love, I need a shower!”

and if you flush the toilet whilst it’s going on the showeree gets scalded 😉

mc i’m also not convinced a nrv would work. i think we need to isolate the hot and cold for a long term solution.

i was hoping someone would post a nice twin tap shower jobbie i could use but it looks like they dont exist.

should have installed a leccy shower to start with – hindsight and all that.