CH Pump requires constant bleeding

[Sime]

We have a Glow-worm Space saver 65-75 (conventional boiler).

We are forever getting air in the system and have to bleed the pump.

We do not get air in the rads and have extended the vent pipe into the header tank to prevent air being drawn in.

We never have a problem when on hot-water only.

We have tried the pump on all 3 settings.

Could anyone please help - all assistance and advice gratefully received - especially in this cold weather.

Sime

 

[Slugbabydotcom]

Assuming that you have gravity hot water and that its not sucking in through the vent first of all, then if your pump is old then that could be the source of the air ingress. It doesnt happen often but it does happen. If you were to take the head off the pump it would be proved by the impeller chamber and outlet being rusty red and the inlet being the normal black crud that you expect to see in heating systems.
If the inlet is red as well look further back 'upstream' for the source of air perhaps the packing gland an old rad valve which may leak when the system is turned off

 

[Sime]

I doubt it would be the pump as this was what we first thought and we have since replaced the pump.

We take on board the fact that we may have a faulty valve on a rad - we are checking this out and will report back.