Compression Fittings

Brass compression fittings for copper and plastic pipe, 4–54mm sizes stocked.

Compression plumbing fittings do not require heat or solder. The joint is formed by tightening a nut and compressing the olive onto a copper or plastic pipe, which forms the seal. They can be used on wet pipework, and are suitable for hot and cold systems.

It is critical to avoid over tightening, if the nut is overtightened the olive will deform improperly causing the joint to fail. A good rule of thumb is to tighten the nut first by hand until it is too difficult to continue and then tighten the nut one half turn more with the aid of a wrench (the actual amount varies with the size of the fitting, as a larger one requires less tightening). The fitting is then tested, if slight weeping (leak) is observed, the nut is gradually tightened until the weeping stops.

Thread sealants such as PTFE are unnecessary on compression fitting threads, as it is not the thread that seals the joint but rather the compression of the olive sealing the pipe against the fitting. However, a small amount of plumbers grease or light oil applied to the threads will provide lubrication to help ensure a smooth, consistent tightening of the compression nut.