Plumbing is defined as the practice, materials, and fixtures used in installing, maintaining, and altering piping systems connected to sanitary drainage, ventilation, and water supply. The major categories of plumbing systems are potable water supply, drainage and venting, sewage/septic systems, and some include graywater recovery. Common tools used in plumbing include press fitting systems to connect pipes, pipe benders to shape pipes, borescopes to inspect drains, plumber's tape to prevent leaks, various wrenches, tape measures, screwdrivers, hose cutters, plungers, and torches for soldering copper pipes.