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Air in the rads - and "bubble" noise

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Have been to a number of heating systems in the past few days where the owner had to regularly top up the water pressure and bleed some of the radiators frequently.

There are a number of possible causes. Assuming there are no obvious water leaks, which must be dealt with first, 2 main culprits seem to prevail. Firstly, compression joints. These convenient connection media are able to admit air without necessarily leaking water. Neat huh? The system pump is able to exert a degree of depression on the water circuit, and from time to time a tiny amount of air can be pulled past the olive. The fix? If the idea of draining the system and undoing every compression joint (including those on the rad valves) to apply jointing compound and re-tightening the joints fills you with the desire to throw yourself off a bridge, you can try nipping the joint(s) up using a GOOD spanner. Don't go mad.

The other (more common) means of air getting sucked in to the system is via the radiator valves. These simple animals use a rope/graphite grease gland seal around the spindle. You can often tell which ones are not good because the spindles are rather easy to turn and instead of being bright brass coloured, they have gone dark. The answer is to nip up the gland nut a few flats. We have found that the worst offenders are the UK ones! The particularly bad ones are "Cosmos" and "Nova". These are cheap and made in China; nuff said. Not sure how they appeared in France, but....

If you have pump shut-off valves, don't forget to nip the gland nuts on these too. The pump will draw air in readily.

I've taken to going round all glands after the initial high temp run and nipping them up - surprisingly few are tight.

Can be other things, of course. These are the things found recently.

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