combi boiler

On a normally-working system, you hardly ever need to top it up. I think we do ours maybe once a year. I'd prefer to know when it gets topped up, as frequent top-ups indicate a fault.

Perhaps you should find where it's leaking - it might be doing some mischief ;->

yes - essentially a pressure reducing check valve usually set at 1 bar - but as others have said they are not "a good thing"

there used also to be a regulatory requirement to disconnect the filling loop between use but I don't know if that is still in force. I do know it's commonly ignored :)

My company office heating has one. It happily carried on topping up the pressure after a leak developed during the Christmas shut down a couple of years ago. It turned what would have been a small puddle into a major flood!

Mike

If it's going down, you have a leak!

Some boilers have a built in filling circuit and no loop. Plus no one ever disconnects the loop :)

Yes. Its called a pressure vessel

If it has lost its ait., pump it up to a couple of bar.

If it's full of water, replace it.

Ah, thanks. A little digging shows one can now leave domestic connected if fitted with a Type BA or CA backflow prevention device.

Plus no one

presumably "when an inspector calls" there's always (a) rapid application of spanner or (b) a choccy bikkie by-pass ;)

Finding it is the problem.

Yup, see if you can find someone who sells a "non leaking primary system"!

The one I installed was non-leaking -- IIRC, no pressure drop in

After about 12 years, the O-rings on the radiator blanking plugs started leaking (not enough to be wet, but some crystalised salts are visible). Even so, it hasn't needed topping up more than once a year.

I have bought a load of nickle plated taper blanking plugs to seal on the thread rather than by O-ring, but not got around to fitting them yet.