Combi boiler and external vent dripping

[ss]

Combi boiler Baxi 100HE I have 2 small leaks at radiator valves, about half a cup a month. I am not plumbing experienced so wont tackle the leaks until the heating goes off in Summer (just in case) so every couple of months I need to top up the pressure. I mention this in case it is relevent.

Today I noticed the external vent had some water come out of it, from what I can gather it was around the time the heating came on at 5pm, I checked later and it appears to have dried up, so maybe a one off.

It is unlikely that I over pressured the system as I have done this many a time and pressure to 1.5 bar.

I will check again tomorrow to see if it vents if so what should I next check. If not why a one off as never noticed this before in the 2 years been in the house.

[gremlin_95]

When the heating comes on again, watch the pressure gauge and see how much the pressure rises.

We do have a sealed system FAQ but the link doesn't seem to work anymore

[ss]

OK, I can check this tomorrow as the heating is normally off all day so can switch it on and see how the pressure gauge reacts.

[John Rumm]

Ed's original web site was taken down some time back I believe. I have recreated the FAQ here now:

[Broadback]

This happened to me a couple of months ago. In my case it was bad news the expansion vessel had gone tilt. Very expensive to haver it replaced, as a compromise (half the price) I had an external one fitted.

[RobertL]

If by "vent" you mean the pipe where the burnt gases come out: The water mi ght well simply be combustion products (water) that have condensed in the l ast part of the flue before exiting the house. This can happen when the thi ng first fires up.

The need to top up the CH loop might mean a leak but it also might mean sim ply that the accumulator needs pumping up; the overpressure valve is lettin g out a litle water each time the system heats up. When you add water to th e CH circuit does the pressure jump back up very fast? If so then that sug gests the accumulator needs pumping up. A car-type air pump will usually d o the job. In mine you depressure the CH, then pmup the bag to 1.5 Bar IIR C, then repressurise. Takes 10 minutes.

Robert

[ss]

No its not the gas vent.

This morning the pressure was at cold 1.25, I turned the heating on and it rose to 2.5 over a period of 15 minutes or so, no water this time at the (external pressure vent?) although the cold water pressure had dropped a little probably due to the 2 small leaks at the valve.

I assume by previous posters comments it is likely that the `accumulator` needs pumping up?

[newshound]

Possibly, or the diaphragm in it may have failed as another poster has described. In that case you should notice water coming out of the "inflation" valve when you prod the pin in the centre. Unfortunately, some vessels are not very accessible for pumping up.

[ss]

I have downloaded a PDF on the boiler and it looks like I may well be fotunate in that the vessel is accessible by just removing the main cover.