Water Hot then cold - help please

danyorks

Hi guys,

Just recently our combi boiler has started outputting hot/cold/hot/cold when running a bath, sometimes it is fine but most of the time you will return to a cold/tepid bath. It doesnt seem as bad through the taps.

Is this a common problem that could be fixed via DIY or at least something I can read up about so I dont get fleeced by a plumber.

Cheers in advance.

Dan

FLAPJACK

We have the exact same problem, plumber told me that the boiler has a vessel which holds a small amount of hot water then when this is empty the water comes through the boiler straight from the main (obviously cold). As it flows throught the heat exchanger the water is heated up (to a fixed max of 50f-on our boiler), the trick is (and it does work) is not to open the hot tap fully thus the water gets hotter by going through the boiler slower. Of course this is a pain as it takes an age to fill a bath! also never fill the bath with both taps open ...just the hot one..you can always cool it down with the cold tap but you can't heat up a full bath.
Just a thought aswell ...have you got the thermostat turned up high enough..I know when we have the central heating on the water seems to be hot pretty quick compared to when it's off.
And these boilers are supposed to be an improvement?

Hope that helps.

danyorks

Yeah that makes sense and I have been using that method to good effect until recently when it still isn't enough, it also happen with the shower too and that was never an issue.

I've read on certain sites that it could be a heat sensor which could be replaced? Whatever it is I'm just hoping it's not a big fix. ££££

Any ideas anyone?

Cheers

Buster1874

What sort of combi boiler is it? Our Baxi (Along with a few other types) has a small rubber diaphragm in a valve underneath the front cover that splits, causing the problems that you have described. Costs about £7 or £8 from Ebay, takes about 20 minutes to change.

danyorks

Buster1874 wrote: »

What sort of combi boiler is it? Our Baxi (Along with a few other types) has a small rubber diaphragm in a valve underneath the front cover that splits, causing the problems that you have described. Costs about £7 or £8 from Ebay, takes about 20 minutes to change.

The boiler is a Saunier Duval, French make I believe.

It was installed only two years ago by the previous house owners.

Could this have the rubber diaphragm you've mentioned?

Cheers

Pincher

danyorks wrote: »

The boiler is a Saunier Duval, French make I believe.

It was installed only two years ago by the previous house owners.

Could this have the rubber diaphragm you've mentioned?

Cheers

Two year warranty.

http://www.saunier-duval.co.uk/catalogsitelet/liste.asp?cn=BOILERS

Gas_Man_4

Hi there,

not familiar with that particular boiler, send over the model and i will have a look into it for you though.

But often a flow sensor can go, the flow sensors in combi's initiate the sequence of either turning on the burners and changing over the diverter valve, or just changing over the diverter valve if the cen heating was already on.

A blocked/scaled heat exchanger would cause probable lock out/by overheating - Not your problem

either way, not for a diy'er in my opinion.

jai247

Hi
I am having the same problem with my shower it starts off hot then goes cold. I don't seem to have that problem with my kitchen sink taps or my bathroom taps.
Last year I had the heat sensor replaced but the problem seems to have come back.
I have a Gledhill SysteMate 2000 boiler.
Can anyone help.