Old plumbing

Still have a water tank in the loft? Even with the lid on , some debris will get in over time and can clog the valve, not to mention debris in the pipework.

There are many small problems that can occur with them but if you haven't switched to a combi yet, best to make sure they're well insulated and covered as far as possible.

The valve on this one wouldn't close, but fortunately it had a working overflow so the continual filling was ejected outside.