Joining 4 Drain Pipes

PVC to PVC

• Many modern drain pipes are made of PVC plastic. PVC is joined to another piece of PVC by coating the joints with a special primer, followed by an adhesive, and pushing the joints together to make a firm and watertight seal. Make sure to slightly turn the pieces as you push them together to evenly spread the adhesive and help the pieces bond together.

PVC to Metal

• PVC comes in both smooth ends and threaded ends. If you are working with a 4-inch metal pipe, join them together with a threaded PVC pipe coupling. Before joining them together, spread pipe dope or plumber's tape over the threads and tighten them securely using a pipe wrench.

Rubber Couplings

• The easiest way to join 4-inch drain pipes together is by using a rubber coupling. These couplings slide over each end of the pipe, and hose clamps secure them in place. Because the drain line is not pressurized, rubber couplings are just as effective as threaded couplings. For ease of installation, cover the ends of the pipes to be coupled with petroleum jelly. The rubber will smoothly slide over the pipe, and once in place, the hose clamp is tightened securely.

Saddles

• A saddle coupling is used when a new drain pipe is added into an existing drain pipe at an angle, particularly when draining into a concrete or clay drainage pipe. The original drain pipe is cut at the top, or the crown of the pipe, to accept the spigot of the saddle. The spigot is inserted into the hole, and the saddle is sealed using mortar, solvent or a saddle collar, depending on what type of pipe is tapped into. For example, a PVC saddle to a PVC pipe would be sealed with solvent, but a PVC saddle to a concrete pipe would be sealed with a saddle collar.

Metal-to-Metal Coupling

• Metal-to-metal drain pipes are generally threaded together to make a tight, waterproof connection. But when joining two dissimilar metals, like copper and galvanized steel, a dielectric coupling must be used. If a dielectric coupling is not used, the steel and the copper react by galvanic corrosion. The steel will degrade and over time, which causes the joint to leak and eventually warrants a replacement.