hot water pressure fluctuation

[gaz2923]

I have an ariston eurocombi and when i turn the shower on (mixer taps) it comes on and then pressure drops and it goes off, another quarter turn, back on, then off, another quarter turn, back on and stays on

it only stays on for around 2 - 3 seconds so i know when i go in the shower i have to do it a couple of times before i get in but its annoying

any reason why it does this?

 

[chrishutt]

Mixer tap showers don't work very well with combis. You need a thermostatic shower valve.

 

[ChrisR]

And some of those can oscillate - t.valve wants to make output cooler so it reduces the hot flow, which therefore gets hotter. So output gets even hotter so hot flow gets reduced until it turns off and shower goes cold...
And what's the betting there will be sludge in the boiler screwing things up too...

 

[gaz2923]

so apart from fitting a thermostatic shower (which im not going to do) is there anything else i can do to help the situation

 

[ChrisR]

Get the system checked out by someone who understands how it, including your boiler, works. Lots of temps and pressures and flows to measure, plus its history to take into account, to come to a diagnosis.
Fair bet that sludge in the boiler is a key factor.
Lots here on that, have a search.

 

[corgiman]

what about balancing valves on the inlets to the hot and cold water supply to the mixer taps

i have used them a few times and they seem to work ok sorry i forget the name of the maker.

 

[gaz2923]

well the boiler was serviced in november (by previous owner) so would his service be something under which he would have given a guarantee or something of the sort