What's this at the top of my boiler leaking?

FlaatusGoat

Dodgy boiler and I'm trying to get it straightened out before I really need it. At the top I've noticed some kind of valve that's leaking or holding some kind of fruid around it. Can I get a second opinion?

EssexExile

Looks like an automatic air release valve.

ThisIsWeird

Not a biggie. Just wrap a cloth around under it.

Air should be released out that wee plastic knurled screw on the side. Try slackening it a half-turn see if it hisses. If it does, let it carry on doing so until it stops, and then see if water drips out. Provided water isn't jetting out of it - and it shouldn't - undo it and give it all a good clean, smear the plastic thingy - it'll have a pointy end - with sili grease (you bought a tub yet!) and screw it back in. Just nip it up gently.

Every month or so, slacken it to see if any more air comes out.

FreeBear

EssexExile said:

Looks like an automatic air release valve.

Page 54 of the installation manual for the Potterton Promax Plus HE claims it is an automatic air vent for the heat exchanger. Appears to have a bleed screw as well which should be opened when filling the system. Possibly a bit of gunk has built up under the valve seats, so ask the engineer to give it a clean next time the boiler is serviced. Alternatively, have it replaced - Doesn't look to be very expensive at around £15 (assuming I'm looking at the right part).