The model VSR-SG is a vane type waterflow switch for use on wet sprinkler systems using CPVC plastic fittings that use small pipe, i.e. 1"/DN25, 1-1/4"/DN32 ,1-1/2"/DN40 or 2"/DN50 pipe sizes.. It is equipped with a union to accommodate installation in confined spaces. The VSR-SG contains an adjustable, instantly recycling pneumatic retard.