Hi, i was taking a shower and when i finished and turned the hot water off i noticed i could here my combi boiler still working and heating the water. Then when i switched the hot water taps on there is no water coming out of the taps at all. I've had to switch the water fead off to the boiler as it just stays lit. I can hear the water going through the boiler but it wont stop. Any information would be greatly appreciated.