Bleeding the radiators…

and I wonder what if instead of air then water…blood really did come out?*

It’d be a Steven King novel plot. As far as I know, the only domestic object he has has not imbued with evil and had terrorizing humans is central heating.

Ladislav, the Polish plumber comments: ‘Or you have put stiff in header tank. Proper place for stiffs, under patio. That forty quid, pliz. What come after s?’

‘T?’

‘Ny-I thot you vud never ask. Two sugars, pliz.’

*and your central heating system would soon become one big black pudding, obviously.