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Series CKD Compact Diaphragm Check Valves


Designed To Prevent Reverse Flow Of Extremely Corrosive and Ultra-Pure Liquids

Sizes 1/4″ and 1/2″




The “CKD” Check Valves utilize a flexible elastomer disc for their sealing action. This sensitive disc offers very low pressure sealing. In addition, the disc requires extremely minimal pressure to move to the open position.
Since these sealing discs are self-centering, they seal in the identical position every time, allowing more reliable sealing and a prolonged life.

The elastomer disc is kept clean by the constant flushing action of the inlet flow, keeping the sealing area free of particles which otherwise might cause leakage.

Series CKD is available in valve bodies machined from Geon® Grade 1 Type 1 PVC, Natural Polypropylene, Kynar® PVDF, and PTFE. The elastomeric disc is offered in Viton® or EPDM.


Series CKD requires a minimum back pressure of 1/2 PSI to close. When inlet pressure is sensed the sealing disc is pushed off the valve seat opening the valve. In this position the sealing disc is supported internally allowing the valve to operate under high flow conditions with relatively no force or stress on the disc.



Pipe Size (NPT) Orifice Size

IN mm

IN mm

IN mm

3/16″ 4.8
1-1/8″ 28.6
2 1/16″ 52.4
5/16″ 7.9
1 1/2″ 38.1
2 5/8″ 66.7

In 1/2″ piping systems where high flow is required, the 1/2″ Series “CKD” Check Valves may not operate efficiently enough because of its orifice size, 5/16″. In such cases, the 1/2″ Series “CKM” Check Valve should be used.


Check Valves Homepage


The Series “CKD” Check Valves, unlike the Series “CK” and “CKM” Check Valves, depend on gravity for sealing assistance in low flow applications. Series “CKD” Check Valves should be installed so gravity will allow the disc to rest against the valve seat when flow is not present.

IMPORTANT: In liquids having high specific gravities the sealing discs may float. In these applications the valves should be piped so that the disc floats against the seat.

For complete information on installation & maintenance for Series CKD, please click here. Note that this link leads to a document in Microsoft Word format.

For Catalog in .PDF format, please click here.