As with any product, proper installation is critical to accurate performance and reliability. Take care with any type of fitting to ensure generally accepted, good installation practices is also important. There are certain key points to remember, specific to push-in fittings, to ensure a quality installation:
Some push fit fitting limits for use with either plastic or copper tubing. A few can handle both plastic and copper without any change to the fitting. Always check with the manufacturer to ensure tubing compatibility. Ensure that tube dimensions, tolerances, roundness and surface finish are consistent with the manufacturer’s recommendations.
Many push fit fittings allow transition from threads to push-in connection. There are various types of threads used such as NPT, NPTF, flare, compression, BSP and BSPT—in straight, tapered, male and female configurations. Again, check the manufacturer’s specifications to ensure correct mating of threads. Also, most plastic threaded push fit fittings need only be hand-tightened. Over-tightening may cause stress fractures and result in leaks. Your manufacturer’s catalog should give tightening torque value guidelines.
3. General Practices
When making a connection with a push fit fitting, it is essential to cut the tube square and free it of score marks, burrs and sharp edges. Use quality guillotine-style tube cutter for plastic tubing, and plumber’s pipe cutter for copper tubing.Insert the tube through the collet, then past the O-ring, all the way to the tube stop. The collet holds the tube in place, while the O-ring seals on the tube O.D. It is a good practice to pull on the tube to verify it is secure, and then test the installation prior to use. One of the benefits of push fit fittings is that you can quickly disconnect installations for service. Remove the tube by simply pushing the collet in squarely against the fitting. With the collet held in this position, pull tubing straight out.
4. Technical Specifications
In the water industry, virtually all push fit fittings consist of plastic—commonly acetal or polypropylene. Operating parameters of pressure and temperature may vary from one installation to another. Take care and ensure that application operating parameters are within the fittings manufacturer’s guidelines. Check the manufacturer’s catalog for technical specifications.
Generally, plastic push fit fittings suits for pressures from vacuum to 150 lbs. per sq. in. (psi) of pressure, temperatures from 33° to 150° F, and tube O.D.s from 1/4- to 1/2-in. Tube O.D. tolerances should be .001/-.004 in. to ensure proper sealing on the O-ring. In applications where harsh chemicals are present, refer to the manufacturer’s chemical compatibility chart. This is especially important for system cleaning and sanitizing procedures.
5. Connection procedures
With compression fittings (metal or plastic) the various bit parts you assemble as part of the connection procedure. Trying to find a dropped nut or ferrule while working beneath a sink is not a very productive use of time. Similarly, with barbed fittings, the barbed inserts are forcefully pushed into the tube I.D. and then secured by tightening a tiny clamp over the connection. Tees, elbows and other multi-connection fittings become quite a chore to assemble. Push-in fittings eliminate the difficulties associated with these older methods. The components of push fit fittings are self-contained, insertion is simple and quick, and you can do thread tightening by hand. In addition, because they are plastic, push-in fittings lend themselves better to applications where lead exposure from brass is a concern. Their light weight and small size also make them easy to ship and receive and carry around.
6. Components and Accessories
Many push fit fittings manufacturers offer component part sets that allow push-in technology to be incorporated into product housings. The part sets typically include a metal or plastic “cartridge” insert that presses into a pre-determined port in the housing. Push the collet snaps into the cartridge after the O-ring down into its seat. This allows for an integral push-in connection to valves, filters, pumps, etc. Such component part sets employs at the OEM level, making the OEM’s products more user-friendly and thus more marketable. Various accessories enhance the use of push fit fittings. These include locking clips, collet covers and threaded stem adapters to make swivel combinations.