Â is used when testing a pipe for air tightness and this involves stopping up both ends of the pipe and then putting the pipe under air pressure using a testing device.â if the pressure drops then the pipe has failed the test. Liquid drain cleaners don’t have to be bad for the environment! drain out. In addition to the pipes, the corrosive nature of chemical drain cleaners eats away at the rubber or plastic components of the plumbing system. Looking for information on costs for.