Guest Plug, Tube 3/8

The John Guest 3/8" Tube Plug from Reliance Worldwide Corporation seals off any open 3/8" John Guest port quickly and cleanly. Whether you are capping a spare outlet, blocking an unused tee branch, or pressure-testing a new line, this polypropylene plug does the job without tools and can be reused from one job to the next.

The plug uses the same Speedfit push-in mechanism as the rest of the John Guest range. Push it into the collet of an open fitting and the internal O-ring seals it watertight in an instant. When the port is needed again, depress the collet and pull the plug free, ready to reuse. That simplicity makes it a natural part of any installer's kit and a quick fix for ports that fall out of use as a system evolves.

Simple, Reusable Sealing

• Connection: Plug for 3/8" John Guest ports
• Corrosion-resistant polypropylene construction
• Push-fit installation, no tools required
• Reusable and fully demountable
• Ideal for capping, isolating, or pressure-testing lines
• Won't scale or rust like metal alternatives

In water filtration and reverse osmosis systems, ports often go unused as configurations change over time, and an open fitting left exposed is simply a leak waiting to happen. A tube plug provides a clean seal that can be permanent or temporary depending on your needs. It is also invaluable during installation: cap a branch, pressurize the system, and check for leaks before bringing every outlet online, which catches problems early. To remove the plug afterward, depress the collet and it withdraws cleanly with no damage to the fitting. Compact, dependable, and matched to the most common 3/8" tubing in residential treatment plumbing, this John Guest tube plug is a small part well worth keeping on hand.

Stocking a few plugs in your kit also speeds up diagnostics. When a system loses pressure, capping suspect branches one at a time helps pinpoint a leak without tearing the whole circuit apart. Because this plug seals instantly and pops free just as easily, it serves as both a permanent cap and a handy troubleshooting tool, making it a quietly indispensable part of any service kit.