Central heating noises

4 Jan 2007
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United Kingdom

Have a gravity central heating system - Potterton Netaheat (~17 years old) in the kitcken with in/out pipes coming from airing cupboard on first floor (inverted loop?).

The following noises happen and I would like to know whether I need to be concerned or it is fairly standard stuff - perhaps just old or not great install??

In the kitchen I can hear a bubbling noise (air) in the pipes connecting to the boiler.

When the boiler and pump is on (either HW or CH) there is always whooshing and howling noises coming from an indeterminate place. It's not ear-splitting loud or anything, just constant.

Only one of the radiators, in a bedroom, emits a bubbling noise when the heating is on.

Other points: In the summer I emptied and cleaned the F+E tank as it had a load of rust(?) sediment in it. I'm going to get the whole system serviced after Christmas.
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Do you have water in the f&e cistern now?

If not is the ball valve working or is there a closed gate valve on the cistern feed...

If you do drain some water out of a rad and then see if f&e water level has dropped. If it hasn't you have a blocked feed pipe and the system water level is low. Unblock/replace the feed pipe.
Plenty of water in F&E, float valve working.

Closed gate valve on mains feed to float valve and drained about a litre from a couple of rads and the F&E water level dropped accordingly.

Noticed that the water draining from the radiators was very slow - hardly any pressure. Is this normal?

Also, drained from the bedroom rad that bubbles away and there was hardly any water coming out.

All drained water was clear although yellowish tinge.
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One radiator is half full of air, although it certainly wasn't like that a week ago. Unfortuntely the bleed screw has seized up so am going to have to replace the whole valve bit later this week.

The whooshing noise definitely starts when the pump kicks in after the boiler has cut out. Must be air in the system and the pump cavitating. (Although I have absolutely no knowledge or experience on which to base that)

The pump is a British Gas multihead II. It has a black nut on the face under which I assume is a bleed valve. However, when I unscrew the nut, it doesn't come off as I expect - just stays connected to the pump somehow. Any tips for bleeding this type of pump?

Also, next to the pump and above the Y valve is an air vent. Worth bleeding here also?
In theory you loosen the black nut and wobble it around.

In practice these pumps seem to always be self venting.

Multi head pump on a standard system should only be on speed 1 or 2 . With system off undo the black nut pull it forward, and tilt to the side to bleed pump. Or let it run in short bursts with nut undone and this will also vent it
your system is full of shyte, will need more than a service, see faq
Have sorted out the rad valve and now have all rads fully vented and 100% hot. The pump is still making the noises though and I can here gurgling in various places.

Any top tips for chasing air out of a system?

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