Hot and cold shower with combi boiler.

14 Jun 2007
Reaction score
United Kingdom
I have a downstairs combi boiler and upstairs shower. Recently the water temperature in the shower keeps changing from hot to cold to hot constantly. Also this happens when running the hot taps upstairs but downstairs ones are ok. Pressure gauge on boiler seems ok and there are no visible leaks. Any ideas?
Sponsored Links
Would help if you told us what combi it is :rolleyes: My thoughts would be scaled up plate heat exchanger. Not a Vokera Linea is it :?:
Also make sure the w/machine,dishwasher e.c.t. is not turned on as they will draw water
Is an Ariston microgenus and still happens when everything off like washer/dishwasher etc.
Have found that if we run the cold tap in basin at same time then hot water in the shower is more stable.
Sponsored Links
It could be an interaction between shower and boiler if its a thermostatic shower.

Try turning the hot water knob down on the boiler and see if that makes it better.

At least one version of your boiler has no plate heat exchanger. If yours did have a plate HE then as suggested that might have become somewhat blocked.

Thanks very much for all your advice. Will have a look at your suggestions but any other ideas in meantime are very welcome! Linda :LOL:

DIYnot Local

Staff member

If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.

Select the supplier or trade you require, enter your location to begin your search.

Are you a trade or supplier? You can create your listing free at DIYnot Local