Worcester 28CDI compact water going cold

[m0t]

Over the last month I've noticed that the bath tap in the upstairs bathroom will go stone cold every couple of minutes for about 30 seconds. The only way to get hot back out is to turn the cold off and the hot to maximum and then after about 30 seconds it goes back hot again. It doesn't seem to do this out of the downstairs taps.

The boiler is downstairs and about 8 years old.

 

[CBW]

Do you know the age of the property? Could be a failing thermostatic mixer, could be a mixer tap crossing over.

 

[m0t]

Do you know the age of the property? Could be a failing thermostatic mixer, could be a mixer tap crossing over.

House is 1920's, the downstairs pipework is about 15 years old and the upstairs is 2 years old. No mixers anywhere on the pipework except the showers. Bath tap is two lever style taps (one hot and one cold).

 

[CBW]

Could be the shower passing. Are you able to isolate the cold to the boiler and run the bath tap?

 

[m0t]

No - the hot and cold feeds to the downstairs shower are tee'd off the run to the upstairs bathroom. Sounds like it could be a strong possibility given where it is in the pipework

It's an old mira thermostatic shower although I did change the thermostatic cartridge on it a few years ago.

Is there any way to check the shower itself?

Edit: not sure if it makes a difference but the downstairs shower was the main shower until about a year ago but probably hasn't been used by anyone in about a year. Would being unused for so long cause an issue?

 

[CBW]

Are you able to isolate the cold to the boiler and run the bath tap?

So the boiler (assumed combi) will have an isolation valve for the cold inlet feeding the hot supplies, if you turn this off and run the hot tap for the bath it should stop.

 

[m0t]

Sorry, completely misunderstood.

I've just done that and didn't get any water come through

 

[m0t]

To update we had the plate heat exchanger replaced yesterday and now the problem appears to be fixed.

Managed to run two baths without the tap going cold. Not sure if that means it's only a matter of time for the main heat exchanger to go or not?