I've got the same shower as yours. The Pressure Relief Device is situated underneath the can/tank (this is where the water gets warmed up). So i changed the PRD but the water still kept pouring out the PRD. Then i realised that the valve for the PRD is inside the can/tank itself, for which the can/tank has to be changed. I then rang triton to inquire the price of a new can/tank for which the price they quoted was £65. So your better off getting a new shower, which is what i did. I got the aquatronic 2+ from Wickes for £55.
Mr A. Chavda, April 2006