Installing a push fit fitting isn't much harder than putting a cap onto a pen. Once the pipe is cut, cleaned and marked for the fitting depth, all you have to do is push the fitting onto the pipe for a permanent—yet removable—connection. It's that easy, and it's almost that foolproof. For a leak-free connection, you just have to make sure the end of the pipe is cut squarely and is clean and smooth on the outside, and you have to push on the fitting (or push in the pipe) as far as it will go.
The push fit fitting offer a very easy way to connect two pipes.
The Push Fit Fitting Basics
Push fit fittings, also called push-on, push-to-connect or push fittings, generally are designed for use with rigid copper, CPVC (chlorinated polyvinyl chloride) and PEX (cross-linked polyethylene) water pipe. There are also some small fittings that work with polyethylene and other types of plastic tubing for things such as water filters, ice makers and aquariums. Push fit fittings cannot be used with galvanized steel pipe, and most types cannot work with flexible (soft) copper tubing.
There's a push fit fitting for every type of water-supply fitting found in a house, including elbows, tees, unions, shutoff valves, hose bibs, repair couplings and even hookup hoses for hot water heaters. Most plumbing codes permit push-fit fittings inside wall and ceiling cavities, and some fittings can even be buried in the ground (after they are wrapped in a protective tape). If you plan to use push-fit fittings for a large project (which could be very expensive; these fittings aren't cheap), check with the local building department for restrictions on their use.
Push-fit plumbing fittings grip the pipe with a ring of stainless steel teeth inside the fitting, while one or more O-rings inside the fitting make a watertight seal around the pipe. If the pipe is not perfectly round or has rough edges or gunk on its surface, the O-rings may not make a perfect seal, leading to leaks. Likewise, if the pipe isn't cut squarely, it might not push in evenly or extend the required distance inside the fitting for a proper seal. This is why you should cut the pipe with a tubing cutter and not a saw.