i've just extended plumbing into a cupboard for my hotpoint wf445 .the plumbing is working fine right up to the end of the hot intake hose and running freely when not connected to the machine,but when i turn the machine on to work on a hot wash all that happens is a humming noise from the back of the machine or if the cold intake is torned on then it just takes cold water in favour of the hot.ive checked that the filter is clean and know the hose isnt blocked . can anyone help me please. ta.