Water comes back up the hose and leaks out of overflow and shower unit?

I have tried 2 different shower heads and hoses the same happens as soon as the shower head is off the water comes out of the hose fine..put the shower head on the water goes back up the pipe comes out of overflow and a little bit comes out where the hose is attached to unit and then trips all the switches..its most odd :(

tracy
August 2009

what shower is it ?
thats not a overflow its the prd which is a safety device.

where did you get the showerhead from ?

hi-spec plumbing & heating (essex)
August 2009

Super glue would help

frank
August 2009