Midline Valve 372U336 Inline Spring Loaded Check Valve - Lead Free

Our review of the Midline Valve 372U336 looks at whether this inline spring loaded check valve is a practical choice for common plumbing and hydronic tasks. The bottom line: it is best for installers and DIYers who need a compact, threaded check valve with solid mechanical construction and certified lead-free materials. Its single biggest selling point is the heavy duty cast brass body and internal spring design that reliably prevents reverse flow while conforming to NSF/ANSI-61/372, making it suitable where lead-free compliance matters.

Key Features

• Spring loaded check: The internal spring blocks reverse flow so the valve closes quickly under back pressure and helps prevent unwanted siphoning in piping systems.
• Cast brass construction: A heavy duty cast brass body and disc deliver mechanical strength and a stable sealing surface for long service life.
• Lead free certified: Conforms to NSF/ANSI-61/372 so it meets lead-free requirements for potable water and similar use cases.
• Corrosion and dezincification resistant: Material selection reduces risk of dezincification and corrosion in typical water applications, improving reliability.
• Threaded FIP connections: 1-1/4 in FIP threaded ends make the valve easy to install into existing threaded piping without special fittings.
• Pressure rating: Rated to 200 PSI CWP (non-shock), suitable for many residential and light commercial water systems.

Who It's For

This check valve is aimed at plumbers, maintenance technicians, and experienced DIYers who need a compact inline solution to prevent backflow or protect equipment such as pumps and tanks. The brass body and certified lead-free construction make it appropriate for potable water lines, irrigation tie-ins, and equipment inlet protection where threaded connections are already used.

Those working with very high transient pressures, specialty fluids, or who require a flanged connection should look elsewhere. Also, buyers seeking fully welded or non-metallic valves for corrosive chemicals will want a product designed specifically for those environments.

Pros & Cons

Pros

• Robust cast brass body and disc provide durability and a reliable sealing surface.
• The internal spring design closes quickly to prevent reverse flow and protect downstream equipment.
• Lead-free certification and ANSI/CSA approvals make it suitable for potable water applications.
• Threaded 1-1/4 in FIP ends simplify installation into common threaded piping systems.

Cons

• Some users report mixed results on leakage; proper installation and piping condition are important to avoid leaks.
• Rated for 200 PSI CWP non-shock; not intended for systems with high water hammer or shock without additional protection.

Specifications

Model	372U336
Connection	1-1/4 in FIP threaded ends
Body material	Cast brass, dezincification resistant
Certification	Conforms to NSF/ANSI-61/372; CSA approved
Operating pressure	200 PSI CWP (non-shock)
Function	Inline spring loaded check valve for backflow prevention

Our Verdict

The Midline Valve 372U336 is a practical, value-minded check valve for potable water and general plumbing where threaded connections are standard. Its heavy duty brass construction and lead-free certification make it a solid pick for installers who need dependable backflow protection, though careful installation is required to avoid the inconsistent leakage some users reported.

Frequently Asked Questions

Can this valve be used on potable water lines?
Yes. It conforms to NSF/ANSI-61/372 and is certified lead free, making it suitable for potable water systems.

What connection size does it use?
The valve features 1-1/4 in female iron pipe (FIP) threaded connections for inline installation.

Is it suitable for high pressure systems?
It is rated to 200 PSI CWP non-shock; it is appropriate for many residential and light commercial systems but not for applications with severe water hammer without additional protection.