released combi boiler pressure,drained 2 ground floor rads,removed one and blanked off its flow /return 8mm pipes replaced other rad with larger size,pressured up system,tested,working fine until 2days later customer calls to say he has no heating/hot water,boiler also leaking,i was away and another plumber called and found boiler was beyond repair, could it have been anything I did? boiler was about 10-15yr old