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Selecting Tubing Connections

A variety of tubing connections and terminations are available for different types of applications. Here is a brief summary of the most common types of connections:

Hose Barb Termination

Barbed fitting terminations hold on the Inside Diameter (ID) of a tube. They are typically used with PVC, polyurethane, silicone and other rubber and plastic tubing. These types of connectors are designed for one-time installation, but if the tubing is flexible enough they can be removed. They are sized for tubing with inner diameters (ID) from 1/16″ to 3/4″ and 3mm to 19mm. The 1/16″ and some 1/8” barbs have a shroud to provide extra strength.

NOTE: Hose barbs are available in both single barb and multiple barb styles. Single barb designs work well with soft flexible tubing, whereas multiple barb designs function well over a wider range of tubing durometers. Hose barb retention depends on the OD of the barb itself and the sharpness of the barb. Regardless of the barb style, look for well-molded, sharp barbs and consider not only the pull-off force, but also the installation force required to install the tubing.

Pipe Thread Termination

Pipe thread connectors are industry standard, threaded connections that use a tapered male into a tapered female thread and tighten on themselves to seal with the added help of pipe dope or Teflon® sealants. These connectors offer equipment manufacturers the flexibility of a threaded port that will accept many different connections as long as they are standard pipe thread connections. The most common types of pipe threads are NPT and BSPT but others are available.

NOTE: It is important to use appropriate gauging and tightening techniques for molded pipe threads to avoid permanent deformation and/or stripping of the plastic thread of the coupling. CPC recommends tightening plastic threads to hand tight plus 1-2 turns. Adjust for your application as necessary.

John Guest Fittings

These fittings are typically used with 1/4″ and 3/8″ OD semi-rigid and metal tubing in applications requiring low flow restriction on the internal diameter of the tubing. With these connectors, the tube is inserted into the fitting and an o-ring seals on the external diameter of the tube. Mechanical retention is provided by internal retainers that also hold on the Outer Diameter (OD) of the tube. These push-to-connect type fittings provide a tight connection but are designed to enable quick removal of the tubing if necessary. John Guest terminations provide the combination of quick assembly and the use of the CPC quick connect and disconnect.

NOTE: Using properly sized and smooth tubing to attach to a John Guest termination will result in a leak- free seal. There should be no need to remove the tubing, since all disconnects are made with the CPC coupling. Using a John Guest fitting repeatedly as a disconnect can result in scratched tubing and leaks. The need to disconnect is eliminated when integrated into a CPC coupling.

Polytube Fittings

PTF terminations are typically designed for use with semi-rigid tubing such as polyethylene, nylon, polyurethane, etc. They also can be used with flexible tubing as long as the IDs/ODs are compatible. Whereas hose barbs are inner diameter (ID) dependent, PTF’s are inner and outer diameter (OD) dependent. They are sized for .100″ ID x 5/32″ OD, .170″ ID x 1/4″ OD, and .250″ ID x 3/8″ OD tubing and their metric equivalents. These connections have a smaller barb that is more easily removed from the tube and then are backed up with a nut that compresses the tube onto the barb, similar to a hose clamp.

Soft Tube Fittings

These fittings are designed for flexible tubing applications where the tube is installed over a stem, an integral nut slides forward over the tube and tightens against the tubing and the stem as pull force is exerted. This fitting allows for easy tubing removal. They are inner and outer diameter dependent and sized for 1/4″ ID x 3/8″ OD and 3/8″ ID x 1/2″ OD tubing.

Compression Fittings

Designed for use with semi-rigid or rigid tubing, a compression fitting is used to connect tubing or hose to a system. The seal is made between the tubing and compression fitting by squeezing the tubing or hose against the ferrule and body of the compression fitting by tightening a nut to seal and hold. These types of connections also offer free flow without internal flow restriction.





Hose Barb

Need correct tubing ID

PVC, polyurethane and other rubber & plastic tubing

Pipe Thread Termination

Industry standard pipe threads

Attach to piping or rigid tubing

John Guest Fittings

Need correct tubing OD

Semi-rigid and metal tubing - polyethylene, nylon, polyurethane, brass, copper, and mild steel

Polytube Fittings

Need correct tubing ID and OD

Semi-rigid tubing – polyethylene, nylon, polyurethane, etc.

Softube™ Fittings

Need correct tubing ID and OD

PVC, polyurethane and silicone


Need correct tubing OD

Semi-rigid tubing – polyethylene, nylon, polyurethane, etc.