Combi only briefly heating water - passed between plumber and boiler engineer...

[ianmcd]

his is a boiler issue and testing at all outlets indicate this as chances of all taps being broken is massively high.

Which I am afraid tends to suggest your plumber doesnt know what cross over is, it only needs to happen at one thermostatic mixer and all taps are affected.
You have been given the correct way to test it, close the boiler for cold water and open a hot tap if water continues to run even a small amount you have cross over simple

 

[MattB83]

Thank you everyone. We have solved it and... it was unexpected. Got another plumber out to replace a broken shower and fix a leaking bath and radiator. Actually didn't think he would look at the boiler but my mother in law explained the issue and he did some looking around the house.

Turns out the boiler was moved from the garage when they put the new combi in. My father in law, pre-dementia, has done everything in the house apart from the absolute essentials like boiler. He'd put in a hot tap which he'd used to wash the dog after walks. I don't know what the set up was but there's a valve or shut-off to switch the outdoor tap off and this is what has caused the problems. Once this was opened the boiler is heating the water fine.

Unfortunately my, ever frugal, father in law's dementia has made him neurotic about energy usage and he's constantly switching things off - my wife left the living room for 5 mins and he sneaked in to remove the fuse from the electric fire plug and he's been tightening radiator valves with pliers so they can't be turned on by hand - then he forgets. So basically he's got concerned about the gas bill and turned the hot water off, forgotten all about it and no-one else was able to work it out.

Phew

 

[Johntheo5]

So, outside tap was connected to both the cold & hot supplies?.

 

[HERTS P&D]

This is why we are not only Plumber's but detectives.

I do love a bit of Track and Trace.

Andy

 

[Johntheo5]

All thats needed now is a TMV and Jack Russell won't be roasted.

 

[MattB83]

All thats needed now is a TMV and Jack Russell won't be roasted.

Sorry for delay! Don't think it was a mixer tap so must have been a quick hose down before it got hot. It's telling that this man won't let his wife put the heating on unless there's snow on the ground but the spaniel got a warm bath