AWWA C508 Swing Check Valves, Explained

If a spec calls out "AWWA C508" and you're not from the water-utility side of the business, it's a reasonable question: what does that standard actually require, and which of the ductile-iron swing-check configurations we stock is the one that fits your job? (Internally we group these by their Midland 962-series part numbers — our "9620-series" line.) This guide walks through what C508 covers, the difference between the flanged, lever & weight, and UL/FM configurations, where each shows up in the field, and what to have ready when you request a quote — because these are ductile-iron, flanged valves that ship LTL freight and get quoted, not carted.

What AWWA C508 Covers

AWWA C508 is the American Water Works Association standard for ductile-iron swing check valves used in waterworks service. It governs the design, materials, pressure rating, and testing of flanged swing checks built for water utility piping — transmission mains, treatment plant piping, pump and lift stations, and other municipal and industrial water and wastewater applications where the valve needs to bolt directly into AWWA-spec flanged pipe and fittings. Our stocked catalog-designated AWWA C508 models run 3 in. through 10 in. in the standard flanged line, with lever-and-weight versions to 8 in.; a separately cataloged UL/FM configuration is covered below.

A swing check valve built to C508 does the same basic job as any other check valve — it lets flow pass in one direction and swings closed automatically to block reverse flow — but the standard's flanged connection, ductile-iron body, and dimensional requirements are what make it the correct spec for water utility work instead of a general-purpose threaded or wafer check valve.

Flanged vs. Lever & Weight vs. UL/FM — What's Actually Different

All three configurations share the same basic ductile-iron swing-check body casting. What changes is how the disc closes and how the configuration is cataloged:

• Flanged (standard swing). The disc opens and closes under its own weight and the momentum of the flow — the simplest, most common configuration for general water and wastewater transmission and plant piping. Midland's catalog lists a 300 psi rating for these standard flanged models (962003–962010 as stocked).
• Lever & Weight. Adds an external lever and weight arm to the same body, letting the closing force and speed be tuned rather than left to gravity alone. This matters most on pump discharge and other slam-sensitive applications, where an uncontrolled, fast-closing disc can generate a water hammer event. (The catalog does not publish a separate pressure figure for this configuration — confirm with the manufacturer.)
• UL/FM (catalog-designated). Midland catalogs a flanged version of this swing check under a "UL/FM" heading. Apex has not independently verified a specific UL standard, UL file number, FM listing, or FM file number for these valves. Where a project requires third-party certification, obtain the manufacturer's current documentation and confirm the project's requirements before specifying them; a standard flanged AWWA C508 waterworks valve is a different product.

Where These Show Up

The flanged C508 line is standard equipment on water and wastewater treatment plant piping and transmission mains wherever a check is needed to protect upstream equipment from backflow. The lever & weight variant shows up most often at pump and lift stations, where controlled closure protects the station from surge damage when a pump shuts off or fails. The UL/FM-configured models are cataloged separately under Midland's "UL/FM" heading; where a project requires third-party certification, confirm the manufacturer's current documentation before specifying them.

For the underlying physics of why slam happens and how orientation and installation choices affect it, see our Check Valve Orientation & Installation guide and the general Swing Check Valve Guide.

Compliance Note

No lead-free, potable-water, or NSF certification has been verified for this family. Confirm compliance requirements with the manufacturer before specifying these valves for regulated water service.

Spring Kits: The Repair Path

When a C508 valve's body and flange faces are sound but it's leaking back or slamming, a 9620-series spring kit lets you rebuild the valve in place instead of ordering and freighting a whole new flanged body. We stock kits sized to match every valve in the line — see the complete cross-reference and the kit-vs-replacement decision framework in our 9620-Series Spring Kits guide.

These Ship LTL and Are Quoted

Ductile-iron flanged valves in these sizes are freight items — they ship LTL, and pricing depends on quantity, destination, and freight class. Rather than list a single price per size, the fastest path to an accurate number is to send us the size, configuration (flanged, lever & weight, or UL/FM), quantity, and destination, and we'll turn around a freight-inclusive quote.

AWWA C508 Valves in Stock

• 3 in. Flanged Swing Check, AWWA C508 (962003)
• 4 in. Flanged Swing Check, AWWA C508 (962004)
• 6 in. Flanged Swing Check, AWWA C508 (962006)
• 8 in. Flanged Swing Check, AWWA C508 (962008)
• 10 in. Flanged Swing Check, AWWA C508 (962010)
• 3 in. Lever & Weight Swing Check, AWWA C508 (96203LW)
• 6 in. Lever & Weight Swing Check, AWWA C508 (96206LW)
• 3 in. Flanged Swing Check, UL/FM catalog-designated (96203UL)
• 8 in. Flanged Swing Check, UL/FM catalog-designated (96208UL)

Frequently Asked Questions

What does AWWA C508 require of a swing check valve?

AWWA C508 governs the design, materials, pressure rating, and testing of ductile-iron, flanged swing check valves for waterworks service — the standard that lets a valve bolt directly into AWWA-spec flanged water utility piping. Our stocked line covers 3 in. through 10 in., flanged, ductile iron.

What's the difference between a flanged and lever & weight swing check?

A standard flanged swing check closes under its own weight and flow momentum. A lever & weight version adds an external arm that lets you tune the closing force and speed, which helps control water hammer on slam-sensitive applications like pump discharge.

Are these valves stocked or quoted?

They're carried in our line but ship LTL freight as quoted items — pricing depends on size, configuration, quantity, and destination. Send us those details and we'll turn around a freight-inclusive quote.

What documentation is available for the catalog-designated UL/FM models?

Midland catalogs 96203UL through 96208UL under a 'UL/FM' heading. Apex has not independently verified a specific UL standard, UL file number, FM listing, or FM file number for these valves. Obtain the manufacturer's current certification documentation and confirm the project's requirements before specifying them.

Related Guides

• Swing Check Valve Guide
• Check Valve Types Compared
• Check Valve Orientation & Installation
• Y Strainer vs. Basket Strainer
• Buna vs. Viton Check Valve Seats
• Strainer Mesh & Sizing Reference

Published performance data is general engineering reference, not a certification for your application. Confirm specifics against the manufacturer datasheet or ask us.

Written by the Apex Flow Solutions technical desk — twenty years of industrial distribution experience behind every guide.