Steven Briggs wrote:
In message , RB
writes


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?


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.

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.