Polypropylene Threaded Pipe Couplings

Female x female NPT threaded pipe couplings for connecting two male threads

A female x female NPT threaded pipe coupling connects two components that each have a male NPT threaded connection while keeping the piping in a straight line.

This coupling can be used in a plastic tank installation to connect two threaded accessories, extend an assembly or add a component between two male connections.

The threaded couplings offered by Agrico Plastics are made of glass-reinforced polypropylene with a Schedule 80 design. They are currently available in 1", 1-1/2", 2" and 3" sizes.

Two female NPT connections of the same diameter

Both ends of these couplings have female NPT threads. A compatible male NPT connection is therefore required on each side.

This becomes important when building an assembly around a tank. If one of the components already has a female connection, this coupling cannot connect the two parts directly. A male x male threaded pipe nipple or another configuration will be required.

The nominal diameter of both components must also be checked. The couplings in this category connect two fittings of the same diameter. If the diameters differ, a compatible threaded reducer should be considered instead.

When should you use a female x female threaded coupling?

This type of fitting is useful when two male NPT components need to be connected in a straight line.

Depending on the installation, it may be used between different components in a tank or piping system when the connections, materials and operating conditions are compatible.

However, a straight coupling should not automatically be selected whenever two parts need to be connected. The liquid path and required function may call for another type of fitting, such as an elbow fitting.

Which fitting should you choose for the required function?

This comparison helps avoid a common mistake: selecting a fitting based only on its diameter. First identify what is located on each side and what the fitting actually needs to accomplish.

Pressure and temperature must be considered together

These reinforced polypropylene threaded fittings are designed for the following recommended operating conditions:

• 120 PSI at -17 °C
• 150 PSI at 21 °C
• 90 PSI at 65 °C

The maximum value of 150 PSI therefore does not automatically apply at every temperature.

The compatibility of polypropylene with the liquid being transferred must also be verified. In a complete installation, allowable operating conditions may be limited by a valve, bulkhead fitting, hose or another component in the system.

The fitting should therefore be evaluated as part of the actual installation, including verification of the dimensions of the final assembly.

A mistake to avoid: two female connections do not connect directly

When looking at an installation, it is easy to focus on diameter and overlook the connection type on each component.

A female x female coupling is designed to receive a male connection at each end. If you try to connect it to a valve, bulkhead fitting or another accessory that also has a female NPT outlet, a male connection will be missing between the two components.

A male x male threaded pipe nipple may then be required, depending on the installation.

Building the connection around the tank

In a tank system, a threaded coupling may be used with a bulkhead fitting, ball valve, threaded nipple, elbow or other accessories before reaching the final hose or piping.

If the system needs to be disconnected frequently, a Camlock connection may be more practical at certain points. If the piping needs to transition to a flexible hose, a hose barb adapter may be required. If the diameter changes, a threaded reducer may be more appropriate.

The goal is not to keep adding fittings until the components connect. Each additional component should have a specific function in the system.

Frequently asked questions

Can I connect this coupling directly to a valve?

Yes, if the valve has a male NPT connection of the same diameter and the materials and operating conditions are compatible. If the valve has a female NPT connection, an intermediate male component will be required.

What is the difference between a female x female coupling and a male x male nipple?

They perform opposite functions. A female x female coupling connects two male connections. A male x male nipple connects two female connections.

Can I use this fitting to change diameter?

The fittings in this category have the same diameter at both ends. To connect two different diameters, use a reducer compatible with the connections in the installation.