Boiler dropping pressure

Mr_Mister

Bendy_House said:

1 bar is perfectly fine, and wouldn't top it up again unless it goes to 0.8 or below. Your boiler should have been working fine at 1 bar, so I don't understand the water feeling only warm - I suspect you didn't let it run for long enough, or ran it at too fast a rate.

Before doing anything else, can you answer, please - does the pressure vary as the boiler heats up the CH?

Yes I have noticed it does increase from 1.5 to around 1.6 when the heating is on or when the hot water tap is running. 

Bendy_House

Ok, thanks - that's perfectly normal.

Bendy_House

It'll be hard to check if it's coming out the condensate pipe, as this gives out water in normal use. If the pressure loss occurred to a notable degree overnight, then that could be checked, but since it takes days, and can drop seemingly at random, then nah.

As mentioned before, the next standard test is to isolate the boiler from the radiators, so you can narrow it down to either being within the boiler, or it being in the pipework and rads. But this will require shutting off the boiler for the duration of the test - days - and the pressure loss would have to be noticeable. Ie - if it takes typically takes 3 days for the pressure to drop, then it'll take that time to carry out this test - not really practical.

Something inspired I saw on YouTube, tho' I'm not going to recommend it 'cos I don't know if there are any associated issues with doing it, is to add a small bottle of cheap perfume to the system water! Run it as normal, and then go around the house sniffing... The guy claims he's done it many times, and it works. You'll even smell it from the condensate outside, if the system water is coming out that way.

Grey_Critic

We hadn that problem and ntraced it to a radiator valve. It had a slight leak when cold but once the heating was on then it sealed itself. Fitted a new valve and fixed it

JohnB47

What about the engineers who came round. Aren't they supposed to fix the problem under warranty? What do they say about it? Shouldn't they be doing the sort if tests suggested here? Also, couldn't they do a pressure test of the pipework?

macman

JohnB47 said:

What about the engineers who came round. Aren't they supposed to fix the problem under warranty? What do they say about it? Shouldn't they be doing the sort if tests suggested here? Also, couldn't they do a pressure test of the pipework?

The boiler may be under a Vaillant warranty. But the leak is on the CH circuit, which has nothing to do with the boiler warranty.