3-piece PVC-U screw-in threaded union PN16: The quick release fitting

The 3-piece PVC-U threaded union, also known as a union fitting or American fitting, is the essential technical part to make your pipe network sectionable. Designed to withstand a pressure rating of 16 bar (PN16), this screw-on female-to-female (FF) fitting allows two parts of an installation to be separated without having to rotate the tubes on themselves. It is the ideal solution for connecting equipment that requires regular maintenance, such as pumps, filters or heat exchangers.

Ergonomic design for simplified maintenance

The structure of this 3-piece PVC-U (unplasticized polyvinyl chloride) union is based on three distinct elements: two threaded crazy pieces and a movable central nut. Its PN16 certification guarantees optimal resistance to the most severe hydraulic stresses. Unlike a conventional sleeve, the 3-piece union offers complete freedom during assembly and disassembly, allowing a component to be removed from the network in seconds simply by loosening the center nut, even in the most confined spaces.

O-ring sealing and threaded modularity

The screw-in union coupling is characterised by its integrated sealing system and universal compatibility:

• Reliable sealing: The seal between the two sides of the fitting is provided by an O-ring (usually EPDM), ensuring no leakage without the need for over-tightening.

• Gas Tapping (BSP): Inner threads allow direct connection to valves, pump outlets, or nipples without gluing.

• Anti-corrosion resistance: Its PVC-U construction makes it insensitive to limescale, salt, and process chemicals, outperforming metal unions prone to galling.

Installation and implementation advice

To ensure long-lasting PN16 performance, the installation of the 3-piece union must follow a few precision plumbing rules:

1. Thread preparation: Apply PTFE (Teflon) tape to the outer male threads before screwing in the crazy parts of the union.

2. Tube alignment: For the O-ring to perform its role, the two parts of the fitting must be perfectly aligned before tightening the center nut.

3. Tightening the nut: Manual tightening of the central nut is often sufficient thanks to the O-ring. If necessary, complete with a light blow with a strap wrench. Never use multi-tap pliers on the nut to avoid marking or cracking the PVC.

Areas of application: Swimming pool, whirlpool and Pumping systems

This 3-piece union is the standard fitting for all pool and spa pump inlets and outlets. It allows the pump to be removed for winterization or repair without touching the rest of the plumbing. In the irrigation industry, it makes it easy to disassemble solenoid valves and controllers. Its robustness and ease of access also make it indispensable in water treatment plants and industrial processes where periodic cleaning of sensors and filters is required.

Technical characteristics