We moved into a new (to us, but really 15 years old) house last June. A few days after switching the heating in autumn on a loud banging through the heating system and the whole house could be heard. It stopped after a minute or so, after scaring the crap out of both of us, it was pretty loud. A couple of months later it did it again, and I sort of ignored it, assuming everything was normal and that it might be the heating system topping itself up - is this likely? The last time it happened I stuck my head in the airing cupboard and the pipes were shaking around pretty badly, hence the noise I guess. WHen it stops it's accompanied by a big switchy "click" noise but I've not yet worked out what this is coming from.
We have a gas boiler around 15 years old, no pressure gauge on it unfortunately, and in the airing cupboard a cylinder with two pumps. One marked CH Pump goes to the cylinder (eh???) and one marked HW Pump just sits on a vertical pipe traversing the cupboard. Both pumps are Grundfos Selectics and totally silent in operation. A couple of the radiators have slight drip leaks around the valves, which I've totally ignored as they'll get replaced in a year or so anyway.
Is there such a thing as auto-fill heating - and if so what controls it? Boiler?
The other possibly related issue is that I think the pipes under one bedroom are either close together or up against a joist. When hot water comes on there's a bang big enough to wake anybody in the room and putting your hand to the floor in certain areas you can feel the vibrations, it's also nice and warm!
This has only become a question because it's now happening once a day and this may or may not be a coincidence but there are some odd possibly dripping sounds behind one of the walls (no evidence of a leak yet though).