Plastic piping is a common material, sometimes used in very crucial capacities such as plumbing. So when a crack develops in one, you will need a solution quickly. There usually isn't a need to replace the entire length of pipe for cracks since a repair can be fairly simple. If you have a piece of plastic pipe that is in disrepair, here is what you can do to correct the situation.
Step 1 - Determine the Amount of Damage
If the pipe you're dealing with is cracked in between joints all the way down, this is one case where it is best to replace the entire thing. However, if this isn't the situation, you'll need to assess the damage so you know what supplies are needed for the repair. A small hole or crack can be easily fixed with some basic tools, but it is important to note that hairline cracks are actually more difficult to deal with than a larger ones.
Step 2 - Prepare the Pipe
Most cracks can be sealed using a special sealant, but the pipe needs to be prepared for the application. Plastic takes sealant differently than other materials, so you will need to take your sandpaper and rough up the area on both sides of the crack. This will create a better surface for the substance to adhere to. Plastic is porous in nature, but pipes are generally treated first, so the roughed up surface will allow for the sealant to seep in to the pipes surface slightly.
Step 3 - Apply Sealant
Any hardware store will carry sealant that is designed specifically designed for plastic or PVC piping. Apply a thick layer of it over the crack with a small applicator tube. Some will require you to brush this out around the crack after you've applied it. Look at the manufacturer's directions for more guidance on this.
Step 4 - Apply Pressure
The sealant will need to stay in place for several hours before it can adhere completely. You can use small clamps to put the necessary pressure on the pipe during the curing process, but avoid applying more pressure than necessary because this could cause the crack to travel or cause the pipe to shatter. Let the sealant sit for the amount of time prescribed by its packaging.
Step 5 - Replacing a Section
As previously stated, repairing a crack that runs the entire length of the section will require you to replace the pipe. For this you will use a hacksaw to remove the damaged section. Place the new pipe section flush against the existing length. Then, use the same sealant around the connecting edges, and place the coupling joints over the portion where the pieces meet. Make sure to use the sealant around the coupling joints as well to avoid leaks. Place the clamps over the adjoining portions when you're finished to keep pressure on the areas while it dries.