I understand the cold feed has to be [for a electric shower] from the cold supply from the mains, can i tap into this, from a branch, which is coming off the cold pipe has it enters the house, the exact tap in point would be 7 inches along the branch off the cold supply ? i.e the mains come in the house and then theres a branch which feeds a sink i intend to tap into the sink branch some 7 inches above were it joins the cold mains pipe .