What do you phone up that U shaped drain pipe underneath your drain and where on earth can i grasp back replacing one? ...
Answers: The pipe is called a "P' trap. If its copper next it may have a nut on both ends that you can remove, after get a replacement from a plumbing supply or hardware store. If its plastic, at hand could be a nut on either close or one end will own a nut and the other end will be glue on to a fitting. Undo the nut(s) and take the segment to the plumbing supply or hardware store. They should be able to endow with you all the parts you want to replace it.
its called a " P" trap, and can be purchased at a hardware, any where on earth that has plumbing supplies,
ask some one at a hardware how to replace it, they hold screw off cap ,