Following a pre-season bleed and test run, I've noticed my combi boiler pressure dropping slowly.
I was preparing myself for an empty expansion vessel (which I repressurised a few years ago).
Then by luck, I was standing in our utility hall - less often used - and the light managed to catch a slightly darker patch on the carpet. Which was right by the square drain tap for the system.
Yup - it took 1/2 a turn !
The thing is, as SWMBO clearly remembers - that was checked 3 times last year after I flushed and re-inhibited the system. She remembers because she asked me and saw me put the spanner to it, commenting it was no harm to check and re-check.
So, not believing in ghosts, and knowing no one else has been anywhere near it, are we both mistaken in our recollection ?
Or can these things work themselves loose with heat-cycling ? Possibly more likely when old ?
I have heard of debris being trapped in the thread which crumbles, leaving it loose ?