Water Goes Cold

[somersetpaul1969]

I'm having a problem with my water!

The boiler pressure had dropped to zero recently but I got it back up to 1.25 to 1.5ish (Worcester Bosch combi) where it stayed.

Now, when I turn on a hot tap, almost instantly the pressure gauge on the boiler drops to 1 and after a few minutes of hot water coming out of the tap the water turns colder. I turn off the tap and the pressure gauge quickly springs back up to 1.25ish, where it started, the water stays cold.

I can't see any leaks around the house.

Anyone advice on what to look for?

 

[CBW]

I’d certainly feel the flow pipe underneath to make sure it’s not circulating around the heating circuit

 

[somersetpaul1969]

Thanks for the advice. Checked this morning and, although the ignition kicks in none of the pipe work underneath warms up

 

[Justin Passing]

It's normal for the pressure to shift when the pump goes on and off, and go up a little when the boiler heats up.

If you find the boiler stops and starts with a low- medium hot water flow, it'll probably be the hot water heat exchanger clogged, (assuming your boiler has one, which model is it?)
The hw would go hot to cold and repeat.

 

[somersetpaul1969]

Afternoon and to update on this. Yes, the heat exchange plate is clogged, badlyit seems, so is being replaced.
Thanks for the answers and help here