air is getting into my central heating , as fast as i can bleed it out. i
noticed the presssure had risen a few weeks ago, and found air in the upstairs
rads. after expelling it, the pressure rose again over the next few days. i
have checked everywhere for leaks, and found none. i have replaced the expansion
vessels ( i know the domsetic water (( white one)) isnt connected to the heating
system, but i found no pressure in it , and upon disassembly found a split
diaphragm ). The red one had a small amount of water come out the shrader valve
when i emptied the air from it. I took it to mean a possible split, so replaced.
Air pressue in said vessel is correct, but the problem has got progressively
worse each day. Now if i bleed the system,and close the valve on the last ( and
furthest rad ) as soon as air stops coming out, if i give it just ten seconds,
and reopen the valve , there will be no water come out again for several
I havent topped up the water in the system since installing the expansion
vessels several weeks ago. If i had a leak , i would surely have needed to. Its
as if the system is creating the air. If the pump was faulty, would that put air
into the system without water loss? I usually bleed whilst the pump is running
( as suggested by my local plumber ). If i bleed cold, then i can expel all the
air, without finding more, just seconds later, but as soon as the system is
turned on the air reappears immediately..
The system is unvented, and powered by air source heat pump.
Any ideas welcome . cheers