Triton T80z electric shower - water coming out of unit?

My Triton T80z electric shower suddnely started to pour water out of the small pipe next to the normal outlet hosehead pipe, instead of the normal outlet. This small pipe is only about 2mm diameter.
Is that part of the pressure relief device?
What's broken inside? Can it be fixed? replaced?
(Any information, advice, to vinayibm at yahoo.com appreciated)
Thanks!