Fixed Elbow 1/4″ MPT x 1/4″ Quick-Connect Check Valve

Check valves allow water flow only in one direction to prevent backflow.

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This 1/4″ valve can be mounted in any position and an arrow molded into the body indicates direction of flow. They are designed for connection to either plastic or soft metal tube and they are intended for liquids only. Note that they are not suitable for air and vacuum applications.

The inner valve is spring loaded and the fitting produces low headloss.

• Valves with low fixed cracking pressure (i.e 10 cm water column), that have not been activated for some time may take several seconds to reseal
• It is the responsibility of the end user to verify that the product is suitable for his specific application.
• It is also recommended that the non-return valve is regularly checked and maintained.

The post John Guest 1/4″ One Way Check Valve appeared first on H2O Distributors.

Model number: 3/8SCV

What Does the 3/8SCV John Guest One-Way 3/8″ Check Valve Do?

• Prevents backflow by allowing one-directional flow only
• Helps maintain line direction control in under-sink and point-of-use plumbing
• Reduces drain-back issues where reverse flow can empty lines or affect system performance
• Helps protect components that should not see reverse flow

Compatibility checks
Before ordering, confirm:

• Tubing size is 3/8 inch OD (John Guest style push-fit tubing)
• Your application requires a one-way check valve (not a shutoff valve)
• You can install the valve in the correct flow direction by following the arrow on the valve body
• Your existing fittings and tubing type are compatible with push-to-connect connections

Common Compatible Use Cases for the 3/8SCV

• Reverse osmosis systems using 3/8 inch tubing runs
• Under-sink filtration lines using 3/8 inch OD tubing
• Ice maker and refrigerator feed lines using 3/8 inch tubing
• Any point-of-use line where you want to prevent reverse flow or drain-back

What’s Included for the 3/8SCV John Guest One-Way 3/8″ Check Valve

• (1) John Guest 3/8 inch check valve (3/8SCV)

Installation Guidance

Install difficulty: easy

Basic tubing cut and push-fit connection required.

Typical Installation Steps

1. Shut off water to the line you are servicing.
2. Relieve pressure by opening the downstream faucet or dispensing point.
3. Choose an accessible location with enough straight tubing to seat the fittings fully.
4. Cut the tubing cleanly and square.
5. Insert tubing into the check valve ends fully until seated.
6. Confirm the flow arrow points in the correct direction of water travel.
7. Turn water back on and check for leaks.
8. Test flow to confirm water moves forward and does not backflow when the line is shut off.

Replacement Triggers

Replace the check valve if you notice:

• Backflow symptoms returning (drain-back, reverse flow, crossflow)
• Flow restriction that persists after verifying tubing and system condition
• Visible cracking, leakage, or fitting wear
• The valve no longer holds one-way protection reliably

Maintenance Schedule

• No routine maintenance is typically required.
• Inspect connections during periodic system service or if you notice leaks or performance changes.
• Replace if the valve fails to hold one-way flow or if fittings become unreliable.

Common Questions on Check Valves

Q: What is a 3/8 inch check valve used for?
A: It prevents backflow by allowing water to travel only in one direction in a 3/8 inch OD tubing line.

Q: How do I know if this will fit my tubing?
A: It is designed for 3/8 inch OD push-to-connect tubing. Match your tubing size before ordering.

Q: Which direction should the valve be installed?
A: Install it so the arrow on the valve body points in the direction you want water to flow.

Q: Will this work for under-sink filters and RO lines?
A: Yes, it is commonly used in under-sink and RO tubing lines when the tubing size is 3/8 inch OD and backflow prevention is needed.

Q: Will this fix the drain-back or loss of prime issues?
A: It can if the issue is caused by reverse flow or drain-back in the line. Confirm the valve is installed in the correct direction.

Q: Is this the same as a shutoff valve?
A: No. A check valve allows one-way flow automatically. A shutoff valve is used to stop the flow manually.

Q: Do I need tools to install it?
A: Typically, no special tools beyond a clean tubing cutter for a square cut and a leak check.

Match your tubing size, install the 3/8SCV in the correct flow direction, and stop backflow issues with a simple, reliable one-way check valve.

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