Air in Central heating system,pipes making banging noise.

[Mike39]

When room thermostat switches central heating off, there is a sound of air rushing in the system,followed by severe banging noises from the pipes. I have now switched the whole system off until I find a way to cure the problem
Also,when I run the hot water tap to fill the bath,the tap slows to a trickle and eventually stops running.The bath is only one third full at this point.
Any advice would be greatly appreciated. Thanks.

 

[Al-Glasgow]

What type of boiler, Combi or vented (small tank in loft) ?

Have you tried to bleed air out from the pump ?.

Alan

 

[Mike39]

The boiler is a Glow-Worm Fuelsaver Mk2 (Model 40B),and is not a combi. I have a small tank in loft. I haven't yet tried bleeding air from the pump.
Cheers.
Mike.

 

[JohnD]

(This is about the rushing and banging)

Bleed the radiators and see if they have air/gas in them; also what colour the water is that comes out (esp. if black or brown).

Might be worth checling that the f&E pipe from the tank in the loft is actually keeping the syst full of water.

If you can get an assistant to drain a couple of pints out downstairs, while you sit in the loft, you should see an identical amount of water going in to make up the volume (if you have a chemical corrosion ingibitor in the water, as you should, you can tip the bucket back in the F&E tank to save wasting it).

 

[Mike39]

(This is about the rushing and banging)

Bleed the radiators and see if they have air/gas in them; also what colour the water is that comes out (esp. if black or brown).

Might be worth checling that the f&E pipe from the tank in the loft is actually keeping the syst full of water.

If you can get an assistant to drain a couple of pints out downstairs, while you sit in the loft, you should see an identical amount of water going in to make up the volume (if you have a chemical corrosion ingibitor in the water, as you should, you can tip the bucket back in the F&E tank to save wasting it).

I have bled radiators to release air and the water colour was brown. I'll try the other method that you have suggested.
Cheers.
Mike.

 

[JohnD]

Brown water suggests rust which suggests overpumping or constant fresh water going in. Sit by your loft tank while the system is running, and switched on and off, see if there is visible water flow. It might even be pumping over from the vent pipe which is curved over the top of the F&E tank.

A trick to see if the ballcock is topping up, put a glass jar or bottle underneath the inlet, sou should see when water is trickling in (and it can safely overflow into the tank so your are not prevemnting top-up0

 

[Mike39]

Ok,thanks for the info.
Mike.