Self curing leak

[itsfreezinghere]

Just wondered how unusual this is... I found a sizeable puddle on the kitchen work top and assumed I must have spilt something without realising and mopped it up. A couple of hours later and there was another puddle in the same place which I traced to a leak where the flexi hose leaves the hot pipe in the boiler to go up to the CH expansion vessel. I couldn't tighten the joint by hand and couldn't get any sort of tool to it either so I just put a bowl under it to catch the drips which were coming every few seconds and switched off the boiler. I was surprised how little water there was in the bowl next morning and during the second day it stopped dripping completely and has been bone dry ever since, even though I topped up the system and ran the boiler, both of which obviously raised the pressure - it had been dripping when cold and with the pressure gauge nudging the red zone [due to the leak]. No Fernox F4 type sealant has ever been added to the system though five years ago it was dosed with both Fernox F1 and F2. How often do you come across what seemed a serious leak that seals by itself?

 

[Chuck]

How often do you come across what seemed a serious leak that seals by itself?

I'd say this behaviour is unusual but not particularly rare.

Don't expect it to stay sealed permanently. If it's happened once, you can be fairly sure it's just a matter of time until it happens again. Keep an eye on it and get it fixed next time the boiler is serviced, if not sooner.

 

[Chuck]

Incidentally, it's only okay to leave this as is because it's on a sealed CH system so there's a not much risk of more than a small amount of water escaping even if the leak does reopen.

Any other type of system, my advice would be to isolate and get it fixed immediately. Water leaks can (and do) cause a lot of damage.

 

[itsfreezinghere]

Incidentally, it's only okay to leave this as is because it's on a sealed CH system so there's a not much risk of more than a small amount of water escaping even if the leak does reopen.

Any other type of system, my advice would be to isolate and get it fixed immediately. Water leaks can (and do) cause a lot of damage.

Thanks Chuck. The boiler has a number of faults and I was hoping it would limp through to the summer and the end of covid before I finally replace it so I have put a can of Fernox F4 in, not too concerned that this is a rather temporary fix at best. I'd bought it before I was convinced the leak had stopped by itself [it's still dry] so thought I might as well use it. The boiler is 27 years old and is inefficient, noisy and unreliable, but has paid its dues.
A possible side effect - or just coincidence - is that before the leak the boiler's latest problem, only from a couple of weeks ago, was a sticky pump that was often reluctant to start and sometimes refused completely, though usually OK from stone cold, so I was only running it when I was there to watch over it. Lord, the house was cold in the mornings recently! Since adding the Fernox it's worked perfectly. I'm still not trusting it though, so only letting it fire up when I'm there to see it does. Last time a BG engineer started to unscrew the bung on the pump it squirted water in his face. I've since seen on the internet that this definitely shouldn't happen, but he just tightened it back up and ignored it.