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.