Air Separators? Do They Fail?

[RB]

My boilers banging away. The system's been cleaned, drained, flushed, bled 2 or 3 times and had a new pump fitted and tried on all speeds, but still the boiler bangs away. I think it's air, in the system, I can hear it whooshing around the boiler and through the pump. The system's about 9 years old and has been working fine since I inherited it about 6 months ago. The banging became increasingly worse over a few weeks. Once drained and filled and the radiators bled a couple of times, no further air builds up in the radiators, so I don't think air is being drawn into the system once filled. It's more like trapped wind!

Close to the pump, I have what I think is an air separator. It's a cylindrical object (about the size of one of those enamelled tin mugs) with 4 ports. The pump seems to circulate water between 2 ports on one of the flat ends. A 3rd port at the opposite flat and 4th port coming off the top but off-centre both go up into the loft to the header tank, one to the header supply, the other to an open vent. If this thing is an air separator, then it's not working as you can also hear the air whooshing through the circuit.

Can someone confirm it is an air separator and do they fail? It's been painted and there are no visible markings. It looks different to the separators I see around the plumbing/heating supplies, has this design been superseded in recent years? Any idea where I might get a replacement? Any other ideas about the problem?

Thanks in advance, Russell

[Steven Briggs]

In message , RB writes

Yep its an air separator. There is nothing _to_ fail. Its just an empty pot. The water swirls round the outside (of the inside, IYSWIM), the air bubbles migrate to the centre and disappear off up the vent pipe. It is possible though that the vent or feed is blocked or restricted in some way.

[Dave Plowman (News)]

If it's an open system - ie one with a header tank - are you sure it's not pumping over? 'Fresh' water in such a system contains air in suspension, but this should disappear quite quickly. But not if it's pumping over.

[John Stumbles]

I very recently came across one that hadn't exactly failed, but what had happened was that where the feed pipe joined the system had scaled up so that no water was able to get into the system. I've come across this problem before. I think that in hard-water areas such as this (Reading) where cold water from the feed pipe meets hot water in the system scale gets deposited on the pipe walls. Although it would seem that only a small amount of water in the pipework would be involved in depositing scale, remember that although there's no net flow of water from the f&e tank into the system (barring leaks) there's a constant ebb and flow (AC rather than DC if you like) as water in the system expands into the tank and contracts back into the system pipework. Thus potentially all the water in the entire system gets to deposit its scale here.

Whether this could be the cause of the OP's problem I don't know. Case for X200 methinks.