Various kinds of sealers are used with pipe fittings to guarantee a tight, leak-proof fit. Sealing tape is often used with threaded pipes and can be rated as waterproof. "Teflon tape," as it's sometimes called, plumber's tape that is tightly wrapped around the male threads several times before screwing the fitting into the female end. The tape forms a good seal between threads. Slip fit pipe fittings use quick drying solvent cement that "melts" plastic fittings into one another. Some people prefer slip fit pipes and cement because they are easy to connect and form a very good bond. One disadvantage, however, is that the pipe cannot be disassembled later, as with threaded pipes.