i repeat. NO NO NO!!!  First of all it's called PEX piping. They do make a push connect fitting that can be used with PEX piping, but if it is incorrectly installed it can blow apart (big mess!!!). Generally speaking, working with PEX requires special tools and specific fittings and, umm, knowledge and experiance. Also PEX comes in White, Red, and Blue. If the pipe is Grey, it is PB (polybutelene) which does not use the same materials as PEX. Be careful and good luck