Guest Union Tee 3/8x3/8x1/4

The John Guest Reducing Union Tee, 3/8" x 3/8" x 1/4", from Reliance Worldwide Corporation branches a 3/8" line into a smaller 1/4" outlet, making it ideal for tapping a secondary feed off a main supply run in water filtration and reverse osmosis systems. It combines a three-way split with a built-in size step-down, saving an extra reducer and the leak point that comes with it.

This tee is especially useful when a 3/8" main line needs to feed a 1/4" branch, such as routing a smaller line to an RO membrane, a dispenser, or an ice maker while the primary 3/8" run continues at full size. Integrating the reduction into the tee itself keeps the junction compact and tidy, which matters in crowded under-sink and equipment-cabinet installations.

Key Features

• Connection: Tube x Tube x Tube, two 3/8" ports and one 1/4" port
• Reducing union tee combines branching with a size step-down
• Polypropylene construction resists corrosion and scale
• Push-fit collets on all three ports, no tools needed
• Demountable design for flexible reconfiguration
• Reusable across multiple installs and repairs

Installation follows the familiar John Guest process. Cut each tube square and free of burrs, then push it firmly into its matching port until it seats past the collet. The two 3/8" ports carry the through-line while the 1/4" port handles the branch, and each connection seals with an internal O-ring automatically. A gentle tug on each tube confirms the grip. The corrosion-resistant polypropylene body stands up to continuous contact with treated water without scaling or rusting, so the tee performs reliably for years. When the layout needs to change, depress the collet of any port and withdraw the tube undamaged, then reconnect as needed. For clean, dependable branching with a built-in size change, this John Guest reducing union tee is a versatile addition to any water treatment build.

Within the John Guest range, this reducing tee pairs naturally with unions, elbows, valves, and plugs that share the same collet system, so a complete distribution layout can be built and later reworked from interchangeable parts. Combining the branch and the size change into one fitting keeps the junction compact, which is exactly the kind of efficiency that makes crowded under-sink and equipment-cabinet installations far more manageable.