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Series CKS Self Closing Check Valves


In Sizes 1½”, 2″ 3″ and 4″


Designed to provide the same superior performance as the patented Plast-O-Matic diaphragm check valve.

  • Normally-closed design, self-sealing, not dependent upon gravity, mounting position or reverse flow, a significant improvement over ball check valves.
  • Leak-free sealing protects against the potential hazards created by reverse flow corrosive liquids such as acids, caustics and chlorine solutions.
  • PFA encapsulated stainless steel spring provides bubble-tight seal mounted in any position.
  • Rapid closure by spring-loaded support helps to eliminate sudden back-flow water hammer.
  • Positive repetitive sealing: poppet automatically positions itself against seat in the identical location each time for long cycle life dependability.
  • Convenience: In 1.5″ and 2″ sizes, union nuts simplify valve installation, inspection and removal.
  • Minimal Cracking Pressure: Valve begins to open and approximately 1.0 to 1.5 PSI.

Materials of Construction:

Plast-O-Matic Series CKS Check Valves are available standard in Geon PVC (Polyvinyl Chloride), Corzan CPVC, Natural Polypropylene and KynarPVDF in sizes 1½”, 2″ & 3″. Seals are EPDM, or FKM (Viton®). Connections are threaded or socket standard.


1 1/2″ and 2″ design

Series CKS Check Valves are normally-closed in design. They feature a corrosion resistant PFA encapsulated spring which energizes a poppet seal that will neither stick nor chatter and is automatic in action. The valves are not dependent upon gravity or reverse flow and represent a significant improvement over ball check valves. They can be mounted in any position. Even in the absence of reverse flow or pressure, the poppet will automatically reposition itself to seal against the valve seat. The unique poppet will seal in the identical location every time, producing a reliable and repetitive seal.  According to, the spring assisted check valve ensures  piping system and pump longevity “as it helps to mitigate, if not eliminate, the damaging effects of water hammer.”  Regarding the CKS, it is important to note that the spring is completely encapsulated, resulting in no metal contact/contamination with the liquid media.


Flow entering the valve inlet will open the valve by pushing the poppet off the valve seat. In this position, the valve seat is kept clean by flushing action of the internal flow, keeping the entire sealing area free of particles which could cause leakage.

If the inlet flow is stopped, or backflow of a higher pressure is sensed, the spring-loaded poppet will automatically reposition itself, closing off the valve seat. Reverse flow or pressure is not required to close the valve when the inlet stops. If reverse pressure is present it simply creates a tighter seal. 


Dimensions Size Chart:

Pipe Size (NPT) A

IN mm

IN mm

IN mm
Model Number
1 1/2
7.4 188
2.5 64
3.5 89
8.4 213
3.3 83
4.5 114
9.9 251
4.3 109
5.5 140
11.73 298
5.75 146
7.88 200

Specifying a Part Number: Part numbers shown above are PVC bodies, FKM seals, and Threaded PVC connections. To specify a socket connection, change the “T” in the part number to “S”. For example, CKS150VT-NC-PV becomes CKS150VS-NC-PV. To change the seal material to EPDM, change the “V” in the part number to “EP”, for example, CKS150EPT-PV. To change the body and connection materials, replace the “-PV” suffix with the following: For CPVC, use -CP. For Natural Polypropylene, use -PP. For PVDF, use -PF. For example, to change the PVC valve to PVDF, CKS150VT-PV becomes CKS150VT-PF. If you need assistance, please contact our Technical Group at 973-256-3000.

Flow Performance:


Because of its normally closed design the Plast-O-Matic CKS Check Valves can be installed in any position; concern over the valve seat closing due to gravity (as with ball check designs) is of no consequence since CKS valves seal in any position.

For more detailed installation instructions please click here.

CAD Downloads:

Check Valves Homepage