To connect copper to PVC, you generally use a special fitting known as a dielectric union. This fitting is designed to prevent galvanic corrosion, which can occur when two dissimilar metals are in contact with each other, especially in the presence of an electrolyte like water. The union has a copper threaded fitting on one side that you can solder onto your copper pipe and a PVC adapter on the other side that you glue to your PVC pipe. It's important to follow soldering and PVC gluing best practices to ensure a leak-proof connection. Always ensure the water is turned off and the pipes are dry before beginning work, and always wear safety gear.

PVC cement, also known as solvent cement, is used to bond PVC pipes and fittings together, creating a permanent, waterproof seal. To use it, first, ensure that the surfaces are clean and dry. Then, apply a primer if the manufacturer recommends it. Next, apply a thin, even layer of PVC cement to the outside of the pipe and the inside of the fitting. Immediately insert the pipe into the fitting, twist slightly to spread the cement, and hold it firmly in place for 15-30 seconds to ensure a strong bond. Avoid moving the joint for at least 15 minutes and wait 24 hours before testing the system under pressure. Proper ventilation is essential during application due to the strong fumes emitted by the solvent cement.

Joining two PVC pipes of the same size involves a simple process. First, ensure the ends of the pipes are clean and dry. Apply a liberal amount of PVC primer around the end of one pipe and inside the fitting of the other. The primer prepares the surfaces for the cement. After the primer dries (usually a few seconds), apply PVC cement in the same areas. Quickly insert the pipe into the fitting, twist slightly to ensure an even distribution of the cement, and hold in place for about 15 seconds to ensure a strong bond. It's crucial to work in a well-ventilated area since the fumes from the primer and cement are toxic. Also, make sure to use the appropriate type of PVC cement for your project, as there are different types for different applications (e.g., pressure vs. non-pressure). Allow the joint to cure for the recommended time on the cement label before testing or using the pipe.