Rola-Chem 521170 Injection Check Valve 3/8″ Hose Barb x 1/4″ MNPT (PVC) For Chemical Feed Lines
The Rola-Chem 521170 is a durable injection check valve used on pool/spa chemical feed systems to help ensure one-way flow into the plumbing line. It helps prevent pool water from backing up into the chemical feed tubing and supports more consistent, leak-resistant chemical dosing at the injection point.
Key Features
- Part Number: 521170
- Type: Injection check valve (one-way)
- Body Material: PVC
- Inlet Connection: 3/8″ hose barb (for chemical tubing)
- Outlet Connection: 1/4″ MNPT (male NPT) for threading into an injection fitting/port
- Purpose: Helps prevent backflow and supports reliable chemical feed at the injection point
Common Applications
- Chemical injection point on pool/spa return plumbing
- Peristaltic metering pump installations using 3/8″ feed tubing and a 1/4″ NPT injection port
- Replacing a worn, leaking, or stuck injection/check valve in an existing dosing setup
Compatibility Notes
- Designed for systems that use 3/8″ chemical tubing on the feed side and a 1/4″ NPT threaded injection point.
- If your tubing size or injection port size is different, choose the correct barb/NPT combination before ordering.
- Install at the injection point in the correct flow direction (arrow/flow marking if present).
Installation Notes
- Threaded connection (1/4″ MNPT): Use PTFE thread tape or a non-hardening thread sealant compatible with PVC. Tighten snugdo not over-tighten.
- Tubing connection (3/8″ barb): Push tubing fully onto the barb. Use a clamp if your application requires it.
- Orientation: Install so chemical flows toward the injection point; reversing it can block flow or allow backflow.
- Location: Injection points are typically placed downstream of equipment (and after heaters when applicable) following your chemical systems guidelines.
Signs Its Time to Replace
- Chemical line drains backward or loses prime
- Water backs up into the feed tubing or pump line
- Visible leaking at the injection point or around the valve body
- Inconsistent chemical delivery even after confirming pump operation
Related Products
- Rola-Chem Injectors & Injection Fittings
- Chemical Injection Check Valves
- 3/8″ Chemical Tubing
- 1/4″ NPT Injection Fittings
- PTFE Thread Tape
- Thread Sealant for Plastic Threads
Installation & Maintenance Tips
- Flush/relieve pressure before removing the valve, and avoid tightening threaded plastic parts under pressure.
- Keep the injection point cleanscale or debris can prevent the check valve from sealing properly.
- If you service the system seasonally, inspect tubing ends for swelling/cracking and trim back to fresh tubing before reattaching.
- When reinstalling, use only enough thread sealant to sealexcess tape/sealant can interfere with seating or crack plastic threads if over-tightened.
- After startup, verify there is no seepage at the threads and that the feed line holds prime between dosing cycles.
