mixer shower temperature problem - going hot/cold

briwall1 · Posted: Mon Jan 05, 2009 6:04 pm

Hi,
I have a Potterton Performa 28 combi boiler and a gainsborough mixer shower.
The problem I have is the water temperature changes from hot to cold then back to hot.
I had the same problem with a gainsborough thermostatic shower and changed it because I was told the problem was with the shower not the boiler.
We have a service contract with British Gas and it was one of their plumbers who told me to do this after he had checked the boiler.
The boiler is apparently running as it should so no problem there but how do I get over the temperature problem - do I need to fit a pressure reducing valve on the cold water supply to the shower?
Any help would be greatly appreciated.
Thanks
Brian

Dusty4018 · Posted: Mon Jan 05, 2009 6:13 pm

Does the problem occur when there are other demands on this cold supply IE toilet re filling, kitchen tap turned on, washing machine on etc ?.

Do you know the hardness of the water in your area.

bengasman · Posted: Mon Jan 05, 2009 6:22 pm

when you run bathtap, does it stay at an even temperature?

briwall1 · Posted: Mon Jan 05, 2009 7:21 pm

Hi,
There is no difference if another tap is run or the toilet is flushed.
The water is quite hard here, does that make a difference?
Thanks for the replies
Brian

bengasman · Posted: Mon Jan 05, 2009 7:35 pm

Actually I meant: all taps closed apart from only hot bath tap; when you hold your hand in the flow, does it stay even or does it go up and down too?

briwall1 · Posted: Mon Jan 05, 2009 7:47 pm

Hi,
Just tried it with only the bath hot tap running and the shower stays cold, it doesnt fluctuate.
Thanks
Brian

Dusty4018 · Posted: Mon Jan 05, 2009 10:35 pm

Brian,

thermostatic shower units are normally made using two different materials, one revolves inside the other. As limescale damage increases with water temp it is possible that some of the working parts (on the hot side) are becoming scaled up & preventing smooth movement. This will effect the operation. How old is the unit. ?

briwall1 · Posted: Tue Jan 06, 2009 8:44 am

Hi,
I dont have a thermostatic shower, I changed it on the weekend after the gas board plumber told me it would be faulty.
I changed it for a normal mixer shower thinking if there was no thermostat the boiler would control th ewater temperature.
Incidentally I have tried it this morning with the cold tap running in the basin to see if that would lower the cold water pressure but it didt make any difference as the shower still went hot and cold.
Thanks
Brian

diy · Posted: Tue Jan 06, 2009 9:22 am

when you run just the hot tap, does the temp stay even.

briwall1 · Posted: Tue Jan 06, 2009 11:25 am

I have tried running the bath hot tap when the shower is running and the shower stays cold.

Rico99 · Posted: Tue Jan 06, 2009 11:38 am

briwall1,

You not quite understanding what they are asking.

Turn the shower OFF, run JST the BAT hot tap. Does the water from the BATH HOT fluctuate in temp.

Rico

briwall1 · Posted: Tue Jan 06, 2009 1:19 pm

Oh, sorry!
no the bath temperature doesnt fluctuate, it stays a constant temperature.