I have just had a look at a property I own that is rented out. The
combi boiler is installed in the cellar but does not have an overflow
attached to it as it is below ground level and there are no drains.

Will the boiler be fine as it is or do I need to fit an overflow
connection. If I need to fit an overflow, can it rise from the bottom
of the boiler and up to the flue level, before it goes outside without
any problems?

Many thanks in advance for any comments.