Guest 3/8 Union Conn

The John Guest 3/8" Union Connector from Reliance Worldwide Corporation joins two 3/8" tubes inline, restoring or extending a run with a quick push of each tube end. It is one of the most useful fittings in any water filtration or reverse osmosis build, where tubing frequently needs to be lengthened, repaired, or rerouted as a system grows or is serviced.

Whenever a tubing run is cut, needs to reach farther, or has to be rerouted around a newly added component, a union connector makes the join effortless. Each end uses the John Guest collet-and-O-ring system, gripping the tube and sealing it the moment it is pushed home, with no solder, clamps, or threading involved. That speed and simplicity is exactly why installers keep a stock of these on hand.

Why It Earns Its Place

• Connection: Tube x Tube, both ends 3/8"
• Straight union connector for inline joins
• Corrosion-resistant polypropylene construction
• Push-in collets grip and seal each tube automatically
• Tool-free and fully demountable
• Reusable across repairs and reconfigurations

To make a connection, cut both tube ends square and free of burrs, since a clean, square cut is what lets the collet grip evenly and the O-ring seal completely. Then push each tube fully into the connector until it bottoms out past the collet, and tug gently to confirm the grip on both sides. The corrosion-resistant polypropylene body stands up to continuous contact with treated water without scaling or rusting, so the joint stays reliable over the long term. If you ever need to take the line apart, press in the collet and the tube slides free undamaged, ready to reconnect. Reliable, reusable, and matched to standard 3/8" treatment tubing, this John Guest union connector keeps your water lines flowing leak-free through every repair and expansion.

Stocking a handful of these unions means a cut or short tube never stalls a job. Because they integrate with the rest of the John Guest range, a single union can splice together tubing feeding filters, membranes, tanks, and faucets, all using the same tool-free push-fit method. That interchangeability is what makes the system so quick to build, expand, and service over the years.