Had a new boiler fitted jan/feb this year. The plumber tied the ballcock up in the expansion tank in loft to drain the system, subsequently must have damaged the valve as it leaked overnight flooding two floors, damaging and destroying carpets, ceilings, furniture and causing thousands of pounds worth of damage. One ceiling has only just been replaced (due to lockdown) at my expense. They are denying all responsibility. ps. all the work was terrible and they have still not fitted a thermostat to the boiler even though they signed it off saying one was fitted. Ignoring communication.