Triton w7000 used as a hand basin heater does not fill?

Alkl of a sudden our basin water heater is outletting water from the auxillary clear plastic pipe and not flowing through the normal outlet. The little heater is getting warm but the water isn't. I haven't meddled with anything - opened it up and gives me a Coventry phone to call but the number is not recognised. A new roads water main has been installed and thats all I can think it could be. Do I have to alter the water pressure? If so HOW?