Please help .I recently recieved a fibre glass ( i think ) bath.I have found that although the plug hole outlet is 40 mm when i bought a a new waste trap the compression joint cant get enough purchase on the thread of the outlet. have i misssed an obvious factor here? It just seems a bit strange that the trap pipe is just a couple of mill below the fully extended compression joint which makes a deep meaningful joint imposssible . What have i missed? any help apppreciated.I am sick and tired of mopping the floor !!( laugh)