Boiler pressure low repeatedly

FreeBear

JohnB47 said:

Wouldn't a competent plumber/installer have some sort of kit to pressurise the pipework and rads (with the boiler isolated) and therefore confirm if the pressure drop is outside or inside of the boiler?

One would hope that a decent plumber has a hydraulic test pump - They don't cost that much to purchase and are an essential bit of kit if/when installing underfloor heating. Test procedure is to hook up a pump and pressurise the system to at 1.5 to 2 times working pressure (4 bar is typical, although John Guest recommends 6 bar for new UFH installs) and leave for 24 hours. To run a test at these sorts of pressure, the boiler must be isolated as the pressure relief valve will lift at 3 bar and there is a risk of damaging the expansion vessel. The one thing you should not do is use compressed air to do a pressure test - If something lets go, it could do serious damage !

Did a hydraulic test on my system when it was installed. Just one leak was revealed which was quickly repaired. But this work was carried out in the summer and before the boiler was plumbed in, so I could get away with an extended test.

ThisIsWeird said: The simple way to do this, tho' not really convenient at this time of year as heating is required, is to repressurise, and then isolate the boiler from the CH using the valves on the flow and return pipes under the boiler.
Leave it for as long as the pressure drop would usually be noticed, and then check the reading.

But to do a test this way requires a pressure guage to be attached to the heating system somewhere (on a radiator perhaps). It also needs a big dial as the silly little 20-25mm ones found on a boiler just aren't sensitive enough.

velvetti

Thanks all for your very helpful and informative replies.
The boiler company sent someone today and they managed to find a very tiny leak below a downstairs radiator (there was wet dust around it and the laminate floor felt a bit damp nearby). Not sure how I missed it when I checked myself, but anyhow, I’m glad an actual defect was found without a long investigation. Let’s hope this problem is fully resolved.
Thanks again

ThisIsWeird

Brilliant! You lucky thing!!

JohnB47

velvetti said:

Thanks all for your very helpful and informative replies.
The boiler company sent someone today and they managed to find a very tiny leak below a downstairs radiator (there was wet dust around it and the laminate floor felt a bit damp nearby). Not sure how I missed it when I checked myself, but anyhow, I’m glad an actual defect was found without a long investigation. Let’s hope this problem is fully resolved.
Thanks again

Thanks for updating, good news. Hopefully that's it sorted.