3-A Sanitary Check Valve Style – 3S


The 3-A Sanitary Check Valve is an all 316/316L stainless steel check valve with a standard 32 Ra or better finish, (consult factory for finer finish availability) for use in new or existing sanitary systems. The 3S design seals on the ID of sanitary ferrules with 3-A specified materials (standard is EPDM). The valve seals inside fittings such as Alfa Laval Inc. Bevel Seat, and Tri-Clamp®, Q-Line, and S-Line and others with ID dimensions equal to the “F” dimensions listed below under Size & Dimensions. The valve is designed to be easily disassembled for cleaning and spare parts are available. The compact 3S fits inside a single set of ferrules, (ferrules not included) and requires no additional space in the line. The insert design makes it extremely economical when compared to full-bodied valves. The wide variety of seat materials and cracking pressure springs allows this series to be used as a check valve or vacuum breaker. Please specify when ordering.
Note: USP Class VI o-rings can be supplied with certification.

PED Compliance Statement: Due to the unique “insert” design of our 3S, SC, CB, TC, SI, & UV, style check valves, they do not constitute an “identifiable pressure bearing housing” as defined in PED Guideline 1/8. These styles must be installed into either ferrules or fittings to create a pressure bearing housing. Instead, they are classified as “components of pressure equipment” as defined in PED Guideline 1/8. As a result, these valves can be sold in the European Community and no CE Mark is required.

In addition applicaitons where the maximum allowed oerating pressure is 0.5 bar (7.2 psi) or less, do not fall under the PED, regardless of the valve style.

Size & Dimension
Line Size Size Code A B C* D** E F*** G Orifice Diameter
1 H 1 1/16 1.72 2.16 0.38 0.870 1.47 0.476
1-1/2 J 1-1/2 1/16 2.53 3.47 0.38 1.370 2.18 0.890
2 k 2 1/16 3.03 4.13 0.47 1.870 2.59 1.135
2-1/2 L 2-1/2 1/16 3.28 4.59 0.47 2.370 2.85 1.59
3 M 3 1/16 4.59 5.53 0.47 2.870 3.36 2.150
4 N 4 1/16 4.75 6.69 0.47 3.834 4.02 2.699

NOTES (DIMENSIONS TABLE)*Maximum nominal dimension for valve closed.
**Maximum nominal dimension for a fully open valve.
***Valves are designed to function with fittings having these internal diameters. (±0.005)
Consult factory for more information.

Available Materials
  • 316 Stainless Steel (SS)
Pressure Temperature Table

Note: 30 PSI is the maximum recommended pressure drop.

Body Material Line Size Non-Shock Pressure- Temperature Rating
316 Stainless Steel (SS) 1" 1000 PSIG @ 100°F
1-1/2" - 4" 725 PSIG @ 100°F

Seat material and spring material selection may limit the recommended service temperature.
See seat ratings, spring ratings, and body material ratings for their respective recommended service temperatures.
Consult the factory for reduced P-T rating above 100 °F. Standard spring material is 316 Stainless Steel.

Flow Data


Size Cv
1 5.2
1-1/2 16.1
2 27.2
2-1/2 49.4
3 74.9
4 120.0



Note: All flow curves and Cv values presume the valves are fully open with 1/2 PSI cracking pressure springs. Consult the factory for more information.

Valve Weights
1 3SH 2.3 oz.
1-1/2 3SJ 6.2 oz.
2 3SK 13.9 oz.
2-1/2 3SL 1.5 lb.
3 3SM 1.9 lb.
4 3SN 3.9 lb.

Seat & Cracking Pressure Options
Valve Style Size Range Body Materials
Other Options
Allowable Seat Materials Standard Cracking Pressures
Other Options
More Info.
Standard Spring Material
More Info.
3S 1" - 4" 316 SL/316 SS 3-A AFLAS®
3-A Kalrez®
3-A Silicone
3-A Viton®

3-A/USP Class VI Kalrez®
3-A/USP Class VI Silicone
3-A/USP Class VI Viton®

1/2 PSI
1.5 PSI
316 SS