Wear a pair of latex or nitrile gloves to keep your hands clean while handling the salt cell and PVC pipes. Also put on protective eye goggles to shield your eyes when cutting PVC pipe. Use the electronic controls attached to the pool’s plumbing system. Press the “off” button to stop the pump. The salt cell is a cylinder, usually colored white, on a pipe near the control panel. It attaches to the pipe through a pair of plastic PVC rings called unions. Turn the unions counterclockwise by hand until you can pull them off the salt cell. Then, lift the cell off of the pipes. You will need to replace the salt cell with new pipe before you can activate the pump again. Measure the space between existing pipes where the salt cell used to be. Also note the diameter of the existing pipes by measuring across their openings.  Get a new pipe that is the same diameter as the existing pipes. It will fit into any fittings already attached to the old pipes. You will also need 2 straight fittings to connect the new PVC pipe to the old ones. Dry-fit the pipe and the connectors where your salt cell used to be. If the pipe is too long, place it in a vise set on a flat workbench. Use a hacksaw to cut the pipe to size. Some stores may cut the pipe for you if you give them your measurements. Wipe down the pipe ends with a clean cloth. Use the brush included with the purple primer to paint about 3 in (7.6 cm) along the ends of each fitting. Coat the inner end of each fitting as well as the outer portions both the new and existing pipes. Then, wait about 10 seconds for the primer to dry. Take the cap off the PVC cement bottle to uncover the brush. Spread a thin, even layer of cement over the outer ends of the fittings. Also coat the inside portion of the pipes. Spread the cement about 3 in (7.6 cm) as well, covering all of the primer. Set a fitting in each existing pipe. Push the fittings as far as you can to ensure they glue in place. Situate them so the other opening points outwards towards the opposite pipe. Move the pipe to the open space in the plumbing system. Slide the new pipe into the fitting of the lower pipe. Give the pipe a quarter twist to the right to lock it in place. Then, pull the uppermost pipe back and slide the new pipe into its fitting. Avoid activating the pump again until the glue has settled. After about 2 hours, you can drain the pool and add chemicals to convert it to chlorine.

Summary:
Wear gloves and goggles for safety. Turn off the pool pump. Unscrew the salt cell to remove it. Use a tape measure to determine what size PVC pipe you need. Cut a new PVC pipe to size. Brush primer onto the new and existing pipes. Spread PVC cement over the primed areas on the pipes. Place the fittings on the existing pipes. Set the new pipe in place. Wait 2 hours for the glue to dry.