Hot water, cold water, repeat

[halesowenmum]

About 9 years ago now I had a modern Worcester Bosch combi boiler fitted along with a Bosch easyControl thermostat (which is also managed via the easyControl app).

There have been problems on and off with the following: I'm upstairs running the bath and and it gets hot for a wee bit, then warm, then lukewarm, and it just stays at that temperature, it never gets hot - the boiler is working downstairs, I can hear it working, but no hot water is coming out.

In the bathrooms I have literally run GALLONS upon gallons of water down the plughole, a complete waste, because of this, just hoping and hoping that the water might just get hot.

The Worcester Bosch engineers have been out several times and in the most recent visit they have replaced every single hardware component to do with heating of hot water that it's possible to replace, checked the boiler to make sure it's working correctly, plus it's service regularly every 12 months.

What the boiler engineer said to me was that if it did it again after this it would not be the boiler that was the cause but what it could be is where there's a mixer such as at one of the shower controls there could be a crack so that cold water is coming in rather than hot water at times?... That it might reveal a need to take off the relevant hardware, and examine the pipework for cracks.

But then, how come in the bathroom on the floor below where we do not have a mixer for the hot and cold water (it's a single unit but it has two separate feeds/two separate taps one for hot water on for cold) we still have the same problem of cold water coming out of the hot tap in that bathroom as well.

This problem has NEVER happened at the kitchen tap, ever, by the way. Only upstairs in baths, showers, wash hand basins.

In both bathrooms it's intermittent and happens to no apparent pattern whatsoever.

All I know is that I go upstairs to enjoy a nice hot bath and all I can get out of it is tepid water and it's absolutely infuriating.

Is what the boiler engineer said correct in theory?

Is there anything I can do to test or gather more information for people on here that would help with your thoughts of what it might be? Do engineers out there know of problems with the Worcester Bosch boilers that relate to these boiler's hardware, their software, butter to do with the boilers software, the Bosch thermostat, or something else that could be causing this problem?

I'm at a loss of what to do next. Thoughts please!

 

[ianmcd]

Sounds like you have crossover, either from shower mixer or a bath mixer

 

[cross thread]

Turn off the cold inlet to the boiler and see it water runs out of the hot taps is sometimes a indication that a tap/ shower is passing/ mixing

 

[halesowenmum]

Turn off the cold inlet to the boiler and see it water runs out of the hot taps is sometimes a indication that a tap/ shower is passing/ mixing

The engineer did say that whilst going about his testing and replacing items that some water did drip out of the boiler (I think), as you describe.

What would be involved exactly to sort this out then?

 

[ianmcd]

identify the faulty cartridge and change it

 

[halesowenmum]

identify the faulty cartridge and change it

I'm trying to understand, where within the plumbing would that item be and whatsnthe work involved - we gotta rip tiles off walls or what's the scoop?

 

[CBW]

It doesn’t drip from the boiler. The cold inlet to the boiler needs to be isolated, then run a hot tap, if water continues to run, then you have let by as already described above. Finding it in your plumbing system - you’re looking at anything that mixes hot and cold water together. Had a few thermostatic mixing valves fail and give the issue you describe.

 

[halesowenmum]

Thanks - I get what the issue might be but I'm trying to establish - what actual work it will it actually involve. Checking out the issue you describe, what would actually have to be done, and furthermore, what's the possible cost?

 

[Gasguru]

It would require the mixer cartridge in the tap fitting/shower valve to be replaced.
Depending on whether those taps/shower valves have been installed correctly and how old they are determines the cost (and whether available).
Another option is to fit non return valves on the hot feeds to the mixer taps/valves.
Faulty mixers can be intermittent, it's a very rare problem and most plumbers will not have come across the fault.
When you operate a tap all the hot water should come from the boiler (and the boiler hot outlet pipe will be hot) but due to a faulty mixer elsewhere cold water is being blended across the faulty cartridge and into the hot side and pipework.

 

[halesowenmum]

It would require the mixer cartridge in the tap fitting/shower valve to be replaced.
Depending on whether those taps/shower valves have been installed correctly and how old they are determines the cost (and whether available).
Another option is to fit non return valves on the hot feeds to the mixer taps/valves.
Faulty mixers can be intermittent, it's a very rare problem and most plumbers will not have come across the fault.
When you operate a tap all the hot water should come from the boiler (and the boiler hot outlet pipe will be hot) but due to a faulty mixer elsewhere cold water is being blended across the faulty cartridge and into the hot side and pipework.

Thanks for explaining, this is what I needed to understand.