There are different materials used for the pipes of your home's water supply; matreials such as cast iron, galvanised iron, steel, copper, cement and plastic (PVC) pipes. PVC pipes are the most common pipes used in private houses. They are relatively easy to maintain, insulate and replace. You can replace and repair the water supply pipes yourself, without any help from a professional plumber. However, check with your local authorities because some cities require a special permit for replacing or repairing water supply pipes.
Locate the exact place on you water supply where you need to replace the pipes. This can be a spot where there is a leak or where the pipe is damaged.
Turn off the main water supply valve. You will need to ask permission from the city waterworks' representative. They will access the main valve located in your house and close it shut.
Dig around the water supply pipe using a shovel. Make a small trench until you have full access to the pipe and a clear working area around the pipe. Dig several feet around the area of the pipe you are going to replace. Dig under the pipe, as well.
Inspect the water pipe now that you have exposed it. Measure the length of the portion of the pipe you need to replace with a tape measure.
Mark the spot on the pipe where you are going to cut. If there is a leak, you should cut at least 15 to 20 cm (6 to 8 inches) away from each side of the leak.
Cut the pipe with a hacksaw or pipe cutting tool. The tool will depend on the material of your pipe. Since PVC is the most common plumbing material, use a hacksaw to cut the pipe. Make sure that your cut of the pipe is straight. Measure the gap you made using a tape measure.
Prepare the pipe you will be installing to replace the damaged pipe. Cut the pipe 1.5 to 3 mm (1/16 to 1/8 inch)shorter than the empty gap in the plumbing. Clean and sand the ends of the new replacement pipe and the ends of the existing pipe. Use a cloth or a sponge for cleaning and a wire brush for sanding the pipe ends.
Dry-fit the length of the new replacement piece in the gap between the two ends of the pipe. The fit should be snug but still not too tight. If the new piece is too short or if it has a gap of at least half an inch on each side, you need to cut a new, longer piece.
Insert the new portion of the pipe into the gap between the two existing ends of the pipe. Use fine sandpaper to smooth the edges of both old and new pipe ends and then slide the PVC couplers on the pipe ends. Apply PVC cement all around the joints to connect the ends of the pipes. Press and hold the pipe ends for two to three minutes until the PVC cement dries.
Check if the replaced section is sealed and turn the water supply on. If everything is functioning properly, cover back the pipe with soil.
When replacing your water supply pipes, consider installing steel instead of PVC pipes. Steel pipes are more expensive but they are far more durable and strong than other water supply pipes.
Never work on water pipes while the water is still on.