Air in pressurised system

[DJB2]

I've recently replaced my Grant Combi oil fired boiler with a new Worcester Bosch Combi gas boiler. I installed the entire OIL boiler system 3 years ago and it had been functioning well until I decided to change to gas on cost basis. With the agreement of my nominated Gas safe registered fitter, I modified my existing pipework (all MDPE with Hep2O push-fit connectors and all new radiators bar one, 3 years ago) to run a short distance to the new gas boiler. The gas fitter ran the gas pipe from the meter and installed the boiler and joined it up to my (hot, cold and CH) pipework. Since then, I have had to drain it and refill it twice (new radiators added). On each occasion I cannot remove all the air from the system. One of the radiators in the house (there are currently 6 downstairs and 3 upstairs) sounds like there is air bubbles running through it and when I bleed it, I get a small amount of air out and then what looks like aerated water (slightly cloudy but clears once sitting for a while). More air seems to migrate to one radiator upstairs as I would expect but no matter how many times I bleed the system, I still get the noisy radiator downstairs.

Any ideas?

 

[Nige F]

when I bleed it, I get a small amount of air out and then what looks like aerated water (slightly cloudy but clears once sitting for a while). .

Any ideas?

A micro leak on the negative pressure side of the pump - drawing in air .

 

[DJB2]

How do I diagnose this?

 

[Nige F]

That`s my diagnosis Do you mean How do I fix it

 

[DJB2]

Apologies, your diagnosis sounds sensible but how do I:

1. Confirm that this is problem?

2. Find the microleak?

Once I've found the microleak, I'm sure that I'll be able to fix it.

D.

 

[DJB2]

ps I wasn't in the house when the gas fitter connected up the boiler but I was told that there was a leak at the 22 mm compression elbow just below the boiler that they dealt with. Since then the pressure seems reasonably stable (although because I keep bleeding it, its more difficult to track) and I cannot see any signs of a leak.

It might also be relevant that at the moment I have 2 pairs of flow and return pipes not connected to radiators because I have to finish decorating first before there are fitted.

D.

 

[Nige F]

Apologies, your diagnosis sounds sensible but how do I:

1. Confirm that this is problem?

2. Find the microleak?

Once I've found the microleak, I'm sure that I'll be able to fix it.

D.

1 difficult to confirm - just an educated guess Had a swimming pool that wouldn`t work once because of a tiny leak . The aerated water gave me a clue , on yours . 2 look @ any joints ( even soldered ones) on new pipework on the suction side of the pump - check tightness of compression joints too . You might find that with pump off you can detect a small amount of water coming out of a suspect joint ( due to system working pressure) It`s a bit of a sod of a job - good luck . PS Shouldn`t be a prob . with the capped off pipes to the ( yet to be fitted ) rads

 

[DJB2]

Thanks Nige, I'll have a look at the Return side of the pipework.

D.