When posting questions, please add as much detail as possible, what is the problem, what you have tried, any possible nugget that will help us help you.
Sorry, I need more to go on than you have outlined.
George from Wolves, September 2008
maybe low mains pressure
tco faulty or the heating elements.
you'll need a multimeter to do some tests.
hi-spec plumbing & heating (essex), September 2008