Hot water stops when cold tap run..

[aim001]

Can you help, When running a bath with the hot tap running, if i turn on the cold tap, all hot water pressure goes...combi boiler is installed nothing wrong with the hot water...always hot but basically stops when the cold tap turned on..any ideas..thanks

 

[newbie1]

my guess cold tap is dropping the pressure so boiler stops

 

[Dave]

Mine does the same.....the cold takes takes pressure away from the boiler and the hot drops off...

 

[newbie1]

fitter should have checked water pressure before suggesting combi they dont suit all situations but people get duped because easy to fit

 

[stevetheplumber]

Can you help, When running a bath with the hot tap running, if i turn on the cold tap, all hot water pressure goes...combi boiler is installed nothing wrong with the hot water...always hot but basically stops when the cold tap turned on..any ideas..thanks

basicly theres not enough flow of water to feed both worth checking that all valves on incoming main are fully open

 

[Bernie2]

If I had a pound for every time I had seen and heard this problem, I would be nearly as rich as Bill Gates.

Combi's are not the get out of problem appliance they are sometimes used as. Saying that nearly all Landlords seem to love them. Easy to see why of course.

My mate and I where once for ever going to a house with a call back of "no hot water". The tenant said when we got there time after time. That the boiler kept going off. Every time we checked it out it was perfect. It was a right puzzle.

However we went there one day and found she was running hot water for three hours to fill her bath. And of course the poor old combi was simply over heating all the time requiring an an auto reset on the overheat stat when it cooled down.

We had been going of course but could not find out why it was overheating and cutting out when we tried it, it had cooled and was working as normal.

The other thing of course was time of day. When we had been going the local water pressure was high and the flow looked okay, but of a night it fell off when she was trying to fill a bath.

We told her the problem and ran. I am afraid the problem seems widespread. People should be told before they get one fitted what can happen.

 

[newbie1]

i think the better ones with higher flow rates coupled with high inlet pressure are ok but with a combination of low pressure and low flow rate they are best used in smaller dwelling

 

[Bernie2]

Hi Newbie1

I agree, unfortunately, to many people, it seems any combi is a combi and they install them just the same. Often if there is room for one, a sealed system boiler with a straight forward hot water cylinder would have seemed a better and simpler choice perhaps. You can get cylinders now with fantastically fast make up times and fairly large capacities as well, that give an excellent flow rate. Even a heat store may have been better. I must admit I am not struck on unvented, I know they are simple, but they do seem to go wrong a lot.

I am one of those Plumber's who like to fit and forget, as do most users of the appliances I find. The combi's good, don't get me wrong, but is their reliability that good?

Mostly the divert valve goes which seems to be the problem with most combi's.

 

[newbie1]

have to say they dont make em like they used to my potterton kingfisher 25yrs old have used 4 thermocouplings and one 3 port valve and yes i know it not efficient but when it eventually goes it will be another system boiler for me ime sure a lot of people sold a combi get bored waiting for bath to fill and worse when in shower and someone turns either cold or hot tap on..prob is most people want cheap cheap cheap combi can work but dont go for bargain bucket and make sure mains pressure is good