Dolphin legacy 10.5 shower?

Can someone point me in the right direction for me to get my hands on the fitting instructions for a DOLPHIN LEGACY 10.5 KW ELECTRIC SHOWER , as i seem to have a spare bit of plastic tube that would seem to fix onto an area of the inlet pipe but i have a blank in place at this time which seems to have a small filter attached , could someone point out what this is please.