Losing Water Pressure

Ben1989

Hi all,

Regularly been losing water pressure. Strong presumption it was due to our old boiler which was failing and presumed the expansion vessel was done.

Had a new boiler installed and still losing pressure so that leaves the pipework I imagine.

What's the best step by step process of discovering this? Adding pressure into the water system is super simple by the boiler but does not identify the issue.

Bendy_House

First things to check - the safety discharge pipe from the boiler which heads outside and points to the ground - this will most likely be 15mm copper. Any sing of damp at the end? Could you tie a wee plastic bag over it to catch any loss?

Then the condensate pipe - this will also usually head outside, but will be larger - ~22mm - and plastic. Liquid WILL be coming out of this in 'slugs' when the boiler is operating, and for a short while after it goes off. But, there shouldn't be any liquid if the boiler hasn't been working for a while.

These are the two basic tests to carry out on an 'older' boiler that could be faulty. Chances are your new boiler won't have these issues, but it would be daft not to check.

The next test is more involving, and you need to be happy to turn valves and stuff... Essentially, you top up your pressure to a noted point - say 1.2bar - turn the boiler off for the duration of the test - ideally for a whole day or overnight (ie, long enough for the pressure drop to be noticeable) - and you shut off the Flow and Return pipes under the boiler that supplies the rads/system.

Ie, you are water-isolating the boiler from everything else.

After the required amount of time, you check the pressure. If it's still at 1.2bar, then it's unlikely to be the boiler. Then you open the valves and observe the gauge - if it drops, then the leak was in the radiator system. If it still doesn't move, then you haven't had a leak, so need a longer period for the test!

Turn BOTH valves fully on before reusing the boiler.