I have an old back boiler that, after draining down and refilling the CH system, is now making annoying gurgling noises, which I don't think it did before.
The noises sound a little like water boiling, and they start a couple of minutes after ignition. Everything else seems to work fine.
Is this anything to worry about? If this is air inside the boiler, how do I get it out? The back boiler is just a box with pipes, no bleed holes.
Thanks, Bart.
The noise is commonly known as 'kettling' - on draining down you've upset/moved/shifted calcium depostits and/or sludge into the heat exchanger - very common on older systems. Treat with the appropriate Fernox or Sentinal additives into the header tank (once partially drained down of course), or a squirt of washing up liquid used to work in the old days. Beware however, you must flush the additives out or they'll eat away at any pin hols on old rads. Maybe a PowerFlush maybe necessary?
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