Stem Reducer, 3/8″ CTS X 1/4″(John Guest)

Description

The 3/8″ CTS × 1/4″ Stem Reducer (John Guest) is a push-to-connect reducer fitting designed to effortlessly transition between 3/8″ CTS (Copper Tube Size) plumbing and a 1/4″ line in water treatment systems. Engineered by John Guest, this compact fitting makes it simple to adapt larger supply lines to smaller tubing without tools, soldering, or glue — ideal for water softener, reverse osmosis, filtration, or auxiliary lines.

Key Features

• Push-Fit Quick-Connect Design
• Installs instantly — push tubing into the fitting to create a secure, leak-resistant connection.
• Size Reduction
• Two 3/8″ CTS connections reduce to a 1/4″ stem — perfect for branching to smaller lines.
• John Guest Quality
• Made from high-grade, corrosion-resistant polymer with stainless-steel grab rings and EPDM O-rings for reliable sealing.
• Reusable & Serviceable
• Can be easily removed using a John Guest release tool for servicing or reconfiguration.

Compatibility

This reducer is compatible with:

• 3/8″ CTS tubing (copper, PEX, CPVC, PE-RT, and HDPE with appropriate inserts)
• 1/4″ OD tubing commonly used for small feed lines, drains, or instrument connections
• Water softener plumbed lines
• RO system connections
• Filtration systems and bypass lines

⚠️ Always verify the actual pipe/tubing OD and type before installation.

Specifications

Fitting Type – Push-Fit Stem Reducer

Primary Size – 3/8″ CTS

Reduced Size – 1/4″

Connection Style – John Guest quick-connect

Material – Lead-free engineered polymer

Seals – Stainless-steel grab rings & EPDM O-rings

Installation – Tool-free push-in (disconnect with release tool)

Applications

The 3/8″ CTS × 1/4″ Stem Reducer (John Guest) is ideal for:

• Water softener supply or drain transitions
• Reverse osmosis system feed or accessory splits
• Connecting smaller instrumentation or sample lines
• Under-sink and utility room installs
• DIY plumbing projects needing size reduction

Benefits

✔ Quick installation — no tools required

✔ Secure sealing — built-in O-rings and grab rings

✔ Versatile — works with multiple pipe materials

✔ Reusable — disconnect easily with a release tool

✔ Durable and corrosion-resistant

Installation Tips

1. Cut Tubing Cleanly: Use a proper tubing cutter for a smooth, square edge.
2. Deburr & Inspect: Remove any sharp edges or debris before inserting.
3. Push Firmly: Insert tubing until it contacts the internal stop.
4. Disconnect When Needed: Use a John Guest release tool to remove tubing for service.

The 3/8″ CTS × 1/4″ Stem Reducer (John Guest) is a simple, reliable solution to size reduction in water treatment plumbing — perfect for applications where fast, tool-free connections and easy servicing are priorities.