I have a shower tray to take out and a bath to fit in its place, the house's water supply is all tank fed with low pressure. I could easily tee into the basin connections for it but im not sure if i should as they are 15mm or if I need to make new connections altogether? Would it be ok to tee into the main feeds in the loft when they come out the tank and run to the bath all in 22mm or is there a better way to do it ?