Watts 9DM2 3/4 3/4 In Bronze Dual Check Valve Backflow Preventer with Intermediate Atmospheric Vent, Female Union Inlet and Outlet Connections

The Watts 9DM2 3/4 is a dual check valve backflow preventer with an intermediate atmospheric vent, rated for non-health hazard applications. It guards against both backpressure and backsiphonage, which is why it turns up on boiler feed lines and similar light commercial and residential connections. It is a continuous pressure device, so it can stay under line pressure without relief.

No. The 9DM2 3/4 is rated for non-health hazard (pollutant) service only. For a health hazard cross connection you need a reduced pressure zone assembly, not a dual check with atmospheric vent. Putting this on a toxic hazard will fail inspection.

Both ends are 3/4 inch NPT. The inlet is a union female threaded connection and the outlet is a union joint, so the unions are part of the valve and you can pull it for service without cutting the pipe. It is an inline body pattern, so it drops into a straight run of 3/4 inch threaded pipe.

No shutoff valves on either end. Neither the inlet nor the outlet carries a shutoff, so if your install or local code calls for isolation you will need to add 3/4 inch NPT ball valves upstream and downstream. It does include a strainer.

It is not a lead free valve, so it is not suitable for potable water lines subject to lead free requirements. The 9DM2 3/4 is intended for non-potable service such as boiler makeup. For a potable connection, specify a lead free model instead.

Rated to 175 psi (12.1 bar) maximum working pressure, with a service range of 33 F up to 250 F. That covers typical hydronic boiler fill duty. Note it is not rated for hot and harsh water service.

Yes, the 9DM2 3/4 is listed as Buy American Act compliant, USA. That matters on federally funded work and on many state and municipal procurement specs.

The intermediate atmospheric vent will discharge water if either check fouls, so it has to be piped or located over an indirect waste or floor drain. There is no cap and tether on this model, and no bypass, so the vent stays open to atmosphere in normal operation.

Bronze/brass body with rubber discs and rubber seats on both checks. The brass finish and body suit standard hydronic and cold water makeup lines. It is not polymer coated.

Order Watts model 9DM2 3/4, part number 61888, from the 9D series. It ships as a kit with the union connections and strainer. There is no meter and no hydrant connection on this configuration.