Plumbing systems made of PVC (Polyvinyl Chloride) are widely used in all manner of residential and commercial construction. PVC pipe is light weight and easy to work with, can readily handle temperature and pressure changes and resists rotting and corrosion, literally for years. However building plumbing systems requires more than just straight pipes, they also need a full range of fittings. Here's a summary of some of the common types of PVC fittings available and and an overview of their functions.
- Elbows are installed between two lengths of pipe to allow for a change in direction usually 45 or 90.
- T joints are so named because they're shaped like the letter "T". They're used to make right angle joints or connections, most commonly to create a right angle branch running off a 'through pipe'. You make the connection by cutting the 'through pipe' and inserting inserting the top part of the "T" joint into the gap then inserting the branch pipe in the leg of the "T".
- When using "T" joints the outside diameter of the insert pipes must be the same as the inside diameter of the "T" joint.
- Coupler are used to join two pieces of pipe. Couplers usually join pipes of the \same size, but you can 'reducing couplers' that allow you to two pipes of slightly different diameters.
- The amount of reduction should never be more than 1/4" because changing the interior dimensions of the pipes will result in pressure differences between the larger and smaller diameter pipe.
Plugs and caps
- Plugs are designed to block the flow of water through a pipe. Plugs can have threads on the outside and screw right into the threaded interior of a pipe, or unthreaded (called a slip plug). A slip plug is cemented into the open end of a section of pipe.
- Caps provide a similar function to a plug and prevent the flow of water, the difference is a cap fits right over the end of a piece of pipe. Similar to plugs, caps can either be threaded or unthreaded. Threaded caps can simply be unscrewed to remove them, but since an unthreaded cap is glued in place, the pipe below a cap must be cut to remove it.
- As the name implies, crosses are shaped like a cross or a 'plus' sign. They are used to divert water coming from a single source into pipes running off in different directions.
- Crosses are usually glued in place - rather than threaded.
Joining PVC pipes and fitting
- Cementing PVC pipe is more properly called "solvent welding", since pipes and fitting are joined using a solvent that literally melts the plastic on both the fitting and the pipe and as the solvent evaporates a solid plastic bond is created.
- Joining PVC is a three step process. The first step is to clean the interior and exterior of both the pipe and fitting to ensure there is no dirt or grease on them. Next a coat of primer (purple primer) is applied to the areas to be joined and finally a coat of PVC cement is applied on top of the primer.
- Join the pieces by pushing them together while turning the pipe a quarter turn to ensure the cement is evenly spread.
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