Pressure valve AND automatic air vent leaking water

The boiler concerned is a Ferroli Optima 701. After fixing a leaking pipe, I've refilled the system but it won't maintain pressure.

Having checked things out I realised it's the pressure release valve has got jammed open when I repressurised the system, and I was about to go out and buy one to replace it when I noticed that the air vent on the small expansion vessel has also been leaking water.

My question is would replacing pressure release valve fix the air vent problem, or do I need to replace both? Is this something I should even think about doing myself or should I call a heating engineer (in which case the number of a good one in sw london would be great)?

Any information much appreciated!

Sounds like the 2 faults are related, water eveident on the expansion vessel valve normally means it has perished(new expansion vessel reqd), the safety valve may have debris stuck in it especially if you used it to drain the boiler.

Thanks very much for that, replacing both seems like the best bet. If I were to replace the automatic air vent, would I need to set the pressure using a gauge and a pump as I've seen mentioned elsewhere on this site?

I think I may have got confused between automatic air vent and expansion vessel, the bit I have dripping is definitely on top of the automatic air vent, not an expansion vessel (that's marked in with dotted lines on my boiler flow diagram and I don't seem to have one, can that be right?).

Thanks again.

hi south yes it does sound like you may be confusing the two. auto air vent is no bigger than 50mm expansion vessel is a dirty great big red thing normally sitting at the back of the boiler with a tyre valve on it.

no you dont do anything to an auto air vent and dependant on the price and ease of fitting you might want to try cleaning it first could be scaled up.

as for the prv try turning it round a few turns it should clunk into place this sometimes cures them

Thanks very much for the tip about turning the pressure valve a few times, it seems to have worked perfectly and valve has clicked back into place.

The problem is much better, but I'm still getting a little water dripping from the automatic air vent. It looks like a nightmare to replace, so how would I go about cleaning it?