There are various methods of joining pipes for water distribution systems. Each method used is designed to withstand internal (hydrostatic) pressure in the pipe and normal soil loads if joints and connections are belowground. Some of these methods produce the types of joints and connections described below.

FLARED AND SWEATED JOINTS. These joints are generally used with copper pipe and tubing. The end of a copper pipe is formed into a funnellike shape so that it can be held in a threaded fitting when a line joint is being made. This method is called FLARING, and the result is called a FLARED JOINT. A SWEATED JOINT is made with soft solder instead of threads or flares. In plumbing, copper pipe or tubing is occasionally fused by heating with a gas flame and silver-aIloy filler metal called SILVER BLAZING (also called HARD SOLDERING).

SOLVENT WELDED, FUSION WELDED, FILLET WELDED, THREADED, AND FLANGED JOINTS. These types of joints are common to plastic pipes. In the production of a SOLVENT WELDED JOINT, a solvent cement with a primer is used. Before solvent is applied, the pipe and fitting must be thermally balanced (caused to have similar temperatures). This process should not be undertaken when the temperature is below 40F or above 90F or when the pipes are exposed to direct sunlight.

FUSION WELDED JOINTS are produced by the use of a gas- or an electric-heated welding tool. The process consists of simultaneously heating the meeting surfaces of the pipe and fitting to a uniform plastic state, joining the components together, and then allowing the two surfaces to fuse into a homogeneous bond as the materials cool to room temperature.

FILLET WELDED JOINTS are made by the use of a uniform heat and pressure on the welding rod during application of the bead. This process can also be applied to repair leaks in thermoplastics.

In plastic pipes, THREADED JOINTS are commonly used for temporary and low-pressure piping since threading reduces the pipe wall thickness. Only certain heavy pipes can be threaded with a special strap wrench. Teflon tape is often used for pipe joint compound when this method of joining pipes is used.

FLANGED JOINTS are extensively used for process lines that are dismantled frequently. Plastic pipes are joined together by the use of plastic flanges with soft rubber gaskets.