for the past month every time you flush the loo or turn a cold tap on the boiler fires up, having looked on google i have checked for dead ends and there are none, one thing we have noticed is the loos are taking longer to fill after flushing so i am assuming there is a drop in the mains presure, also runing two cold taps at the same time there is a noticable slow down in flow. i intend to get the waterboard to check mains pressure but in the mean time i intend to fit a non return valve on the boiler cold supply, is there anything else i could try?