John Guest Quick-Connect Fittings
John Guest - Acetal 4-Way Cross Fitting - Grey 3/8” OD
John Guest - Acetal End Stop Fitting - Grey
John Guest - Acetal Fixed Elbow Quick Connect Fitting - Grey
John Guest - Acetal Fixed Elbow Quick Connect Fitting - White
John Guest - Acetal Inline Straight Ball Valve - Grey
John Guest · Speedfit Quick Connect Fittings
Push-In. Lock. Done.
John Guest Speedfit fittings are the standard for tool-free tubing connections in water filtration, RO systems, ice makers, and water dispensers. Push the tube in once — the internal collet grips it, the O-ring seals it, and it's locked. No clamps, no thread tape, no wrenches.
John Guest fittings are used by water treatment professionals worldwide precisely because they work the first time, every time — no tools required, no thread compound, no clamp rings. Push the tubing into the fitting until it clicks, and you have a leak-proof connection rated to 150 PSI. Available in single units and 10-packs for installations requiring multiple fittings of the same type.
How It Works
The Speedfit Push-In Connection
Cut Tube Square
Cut your tubing cleanly and squarely using a tube cutter or sharp blade. Remove any burrs from the cut end. A clean, square cut is the only preparation required — no deburring tool, no chamfer.
Push In to the Tube Stop
Insert the tube firmly into the fitting until it reaches the internal tube stop. The stainless steel collet teeth grip the outer diameter of the tube automatically. You'll feel a positive stop when the tube is fully seated.
Pull Back to Lock & Test
Give the tube a firm pull-back to confirm it's locked — the collet should prevent any movement. The O-ring creates the leak-proof seal at water pressure. To release, depress the collet ring with your finger while pulling the tube.
Release technique: To remove the tube, press the collet ring (the grey ring at the tube entry) firmly toward the fitting body while simultaneously pulling the tube straight out. Do not twist. If pressure is on the line, relieve it first before attempting to disconnect.
Fitting Types
What's in the Collection
Male Connector (Straight)
Connects a tube to a female NPT or BSPT threaded port. The most commonly used fitting in water filtration — used to connect tubing to filter housings, valve ports, manifolds, and faucet tees.
Female Connector (Straight)
Connects a tube to a male NPT threaded fitting or nipple. Used where the mating component has external threads — common on solenoid valves, pumps, and fittings with male NPT stubs.
Fixed Elbow (90°)
90-degree turn from tube to a male NPT or BSPT threaded port. Ideal where space is tight and a straight connector can't exit cleanly from a port — common behind RO systems and wall-mounted filters.
Equal Tee (3-Way)
Splits one tube line into two, or joins two lines into one. Used to branch a supply line to two filter housings, or combine two return lines. All three ports accept push-in tube connections.
4-Way Cross Fitting
Four-port cross fitting for complex manifold plumbing. Splits one supply into three branches simultaneously — used in multi-stage systems, vending machines, and commercial RO installations. Available in 3/8" OD.
Straight Union (Equal)
Tube-to-tube in-line connector. Joins two tube ends of the same OD in a straight line. Used to repair a cut or broken tube, extend a run, or join two sections of different-age tubing.
Bulkhead Union
Passes a tube through a panel, cabinet wall, or enclosure. The threaded collar secures to the mounting surface from both sides, creating a clean panel-mounted tube pass-through. Available in grey and white.
Faucet Connector (UNS / BSPT)
Connects tubing directly to standard drinking water faucet shanks using 7/16" UNS (US standard) or BSPT threads. Eliminates the need for compression fittings at the faucet tail.
End Stop
Caps off an open tube end or unused fitting port. Used to terminate a tube or close a port during testing or when a branch is not yet connected. Push the tube in — it seals immediately.
Inline Straight Ball Valve
Push-in quarter-turn shut-off valve. Insert tube on both sides for a tool-free inline shut-off — useful for filter housings, individual branch isolation, or service access points. Available in 3/8" and 1/2" OD.
Female Flare Connector
Connects push-in tubing to 1/4" or 3/8" FFL (Female Flare Liquid) fittings — the standard connection on most undersink RO faucets and tank valves. Replaces traditional compression fittings at flare ports.
Reducing Tee / Reducing Union
Joins tubes of different outer diameters — for example, a 3/8" supply line branching to a 1/4" feed line. Used where tube sizes change between system components.
Sizing Guide
Matching Tube OD to the Right Fitting
John Guest fittings are sized by the outer diameter (OD) of the tubing — not the inner diameter or flow rate. Measure the outside of your tube with a caliper, or check the tubing label. Using the wrong OD fitting will result in a fitting that either won't accept the tube or won't grip it securely.
| Tube OD | Typical Tubing Color | Primary Application | Common Systems |
|---|---|---|---|
| ¼" OD | White, Blue, or Clear | RO system feed, permeate, and drain lines | Under-sink RO, countertop filters, ice maker feeds |
| 5/16" OD ★ | White or Blue | RO drain lines, refrigerator supply | RO drain saddle connections, inline feed lines |
| 3/8" OD | White, Blue, or Clear | Larger RO lines, filter housing inlets/outlets | Multi-stage under-sink, water dispensers, vending |
| ½" OD | White or Grey | Main supply lines, filter housing connections | Whole-house pre-filters, commercial systems |
| 5/8" OD | White or Grey | High-flow supply connections | Large commercial filter housings, high-flow systems |
When in doubt, measure the outside of the tube. The most common source of sizing errors is confusing tube OD with the NPT thread size on the mating port — these are two independent dimensions. Your tube may be ¼" OD while the port it connects to is ¼" NPT, ⅜" NPT, or ½" NPT — all valid combinations depending on the fitting you select. John Guest fittings combine the tube OD (push-in side) with the thread size (threaded side) in a single part.
Thread Standards
Understanding Thread Types
National Pipe Thread (NPT)
The US standard for pipe threads. Tapered thread profile that seals by deforming as it's tightened. Used on virtually all US-market filter housings, valve bodies, pressure gauges, and plumbing components. When in doubt, your US-sourced component is likely NPT.
British Standard Pipe Thread (BSPT)
The international standard — used on many European and Asian-manufactured water filtration components, RO systems, and faucets sold in the US market. Parallel or tapered depending on sub-type. Physically similar to NPT but not interchangeable — mixing them will leak.
Female Flare Liquid (FFL)
Standard connection on RO faucets and storage tank valves — the fitting has a flared seat rather than pipe threads. John Guest FFL connectors allow push-in tubing to connect directly to FFL ports without compression fittings or separate adapters.
Unified Special (UNS) — 7/16"
A non-standard thread used on US drinking water faucet shanks (7/16" UNS). John Guest faucet connectors with UNS threads are designed specifically for this application — connecting push-in tubing directly to the threaded tail of a filter faucet.
NPT vs. BSPT: These look nearly identical and will thread together partially, but they are not compatible — mixing them creates a connection that will leak or fail under pressure. Check your component's documentation or the marking on the port body. NPT fittings are typically marked "NPT" or simply not marked at all on US products. BSPT fittings are often marked "BSP" or "G" followed by a size.
Materials
Acetal Grey vs. White — Which to Choose
Grey — Full Product Line
The primary John Guest fitting color — available across the complete range of fitting types, tube ODs, and thread sizes. Acetal copolymer construction offers excellent chemical resistance, dimensional stability, and UV resistance.
- Widest selection of fitting types and sizes
- Used in professional water treatment installations
- Resistant to chlorinated water, mild acids and alkalis
- Rated for hot and cold water applications
- Food-grade acetal — safe for drinking water
White — Selected Styles
White variants are available in a subset of the range — primarily elbow and bulkhead fittings in ¼" and 3/8" OD. Functionally identical to grey but preferred for installations where the fitting is visible and a white color matches the surrounding plumbing or cabinetry.
- Cosmetic preference for visible plumbing
- Same acetal construction as grey — identical performance
- Limited to select fitting types and OD sizes
- Food-grade, drinking water safe
Applications
Where John Guest Fittings Are Used
Under-Sink RO Systems
Every tube-to-port connection in an RO system — feed line from the saddle valve, between filter stages, to the membrane housing, and from the tank to the faucet.
Refrigerator Ice Makers
Push-in connections to refrigerator ice maker and water dispenser inlets — faster and more reliable than compression fittings on ¼" OD supply tubing.
Water Dispensers & Coolers
Feed connections on bottleless coolers, hot/cold water dispensers, and commercial water vending machines. John Guest fittings are specified by many dispenser manufacturers.
Whole-House Pre-Filters
Inlet and outlet connections on standard filter housings where tubing rather than threaded pipe is used — particularly in flex-tubing installations under sinks and in utility spaces.
Lab & Commercial Water Treatment
Light commercial RO systems, water purification loops, analytical instruments, and food & beverage processing equipment — anywhere reliable, tool-free plumbing connections are needed.
System Repairs & Modifications
Straight unions for tubing repairs, reducers for size transitions, tees for adding branches, and end stops for temporary capping during system modification.
Installation
Installing John Guest Fittings Correctly
Confirm Tube OD and Thread Size
Verify the outer diameter of your tubing and the thread type and size of the port you're connecting to. Both dimensions are needed to select the correct fitting. The tube OD determines the push-in side; the thread standard and size determine the threaded side.
Thread the Fitting Into the Port First
For fittings with NPT or BSPT threads, apply a small amount of PTFE thread tape (2–3 wraps, clockwise when looking at the male threads) before threading in. Hand-tighten, then snug with pliers — do not over-tighten acetal threads. The fitting should be snug and aligned, not torqued down.
Cut Tubing Square
Use a tube cutter for the cleanest cut. If using a knife or scissors, ensure the cut is perfectly square and the tube end is not oval or deformed. Any out-of-round condition at the tube end can prevent the O-ring from sealing correctly.
Insert Tube Fully
Push the tube firmly into the fitting until it reaches the internal tube stop — you'll feel a definite stop. The collet teeth grip the tube automatically. Give the tube a firm pull back to confirm it is locked. If it pulls out, the tube was not fully seated — reinsert and push harder.
Pressurize and Check for Leaks
Turn on the water supply slowly. Inspect each fitting visually and by touch for drips or moisture. John Guest fittings seal immediately at pressure — any leak at the tube entry indicates the tube was not fully seated. Release pressure, reseat the tube, and retest.
Not sure which fitting you need? Have the tube OD (measured with calipers), the thread type (NPT or BSPT), and thread size of the port ready. Call us at (877) 541-6603 and we'll identify the exact fitting you need — or browse by tube OD and thread size in the collection above.
No Tools Required
Push in and it's connected. No wrenches, no thread compound, no compression sleeves. Faster than any other fitting type.
Demountable & Reusable
Unlike compression fittings, John Guest fittings can be disconnected, cleaned, and reused multiple times without replacing the fitting.
Leak-Proof at Pressure
The dual-action grip (collet teeth + O-ring seal) is rated to 150 PSI — well above typical residential water pressure of 40–80 PSI.
10-Pack Value
Most fittings available in packs of 10 for significant per-unit savings — ideal for multi-stage installs, commercial setups, or stocking spares.
