Watts 957-NRS 3 3 In SS Reduced Pressure Zone Assembly Backflow Preventer, NRS Shutoff Valves

Yes. The Watts 957 reduced pressure zone assembly in the NRS 3 configuration has 3 inch inlet and outlet, both flanged joint connections, so it drops into a 3 inch flanged run without adapters. Metric equivalent on the inlet is 80 mm. It is an inline body pattern, so inlet and outlet are on the same axis and the assembly runs straight through the pipe line rather than offsetting.

That comes down to what is in the line downstream. The Watts 957-NRS 3 is a reduced pressure zone assembly rated for health hazard protection, which is the level required where a cross connection could introduce something that makes people sick rather than just something objectionable. A double check assembly only covers non-health-hazard (pollutant) applications. The 957 also protects against both backpressure and backsiphonage, so it covers a downstream booster pump or elevated tank pushing back into the main as well as a main-side pressure drop pulling water backward.

Keep it on cold or tempered water. The 957-NRS 3 is rated 33 F to 140 F, so it will not take a domestic hot water supply at typical 140 F plus storage temperatures, and it is not built as a hot and harsh water unit. The 33 F bottom end also means it needs to stay out of freezing conditions. Outdoors, that means a heated enclosure or an indoor location.

Yes, the 957-NRS 3 is a lead free assembly, so it is suitable for potable water service. The body is stainless steel, with silicone check discs and engineered plastic seats.

NRS is non rising stem. Both the inlet and outlet shutoff valves on the 957-NRS 3 are non rising stem gate valves, so the stem stays put as you operate the handwheel and nothing telescopes upward. That matters in a tight vault, a pit, or a mechanical room with a low ceiling, where an OS&Y (rising stem) shutoff would need clearance above the valve to open fully. The tradeoff is that you cannot tell open from closed at a glance the way you can with a rising stem.

Continuous pressure service is fine. The 957 is rated for continuous pressure operation, so it can sit on a line that is pressurized 24/7 (fire line makeup, process feed, irrigation main that stays charged) rather than being limited to intermittent duty. Maximum working pressure is 175 psi, which is 12.1 bar.

Not on its own. The 957-NRS 3 is supplied without a bypass, so testing or servicing it takes the line down. For a hospital, a data center, or any facility that cannot go dry, you need a separate bypass arrangement (a parallel assembly or a piped bypass loop with its own approved assembly) designed into the installation. Everything else about the unit, including the health hazard rating and continuous pressure duty, suits that kind of critical service.

No. The Watts 957-NRS 3 reduced pressure zone assembly is not Buy American Act compliant, so it will not satisfy a federal or state spec carrying a BAA or domestic-content requirement. For a public project with that clause, you need a domestically produced assembly instead.

It ships as a kit: the 3 inch reduced pressure zone assembly body with the inlet and outlet non rising stem gate valve shutoffs. Watts part number 111603, ordered as model 957-NRS 3. A strainer, meter, and bypass are not included, and the body is stainless steel with a stainless finish (no polymer coating).

The 957 uses a stainless steel body and stainless finish, which is why it carries no polymer or fusion epoxy coating the way a cast iron assembly does. For a facility crew, that means no coating to chip at the flange faces or in a wet vault, and no repainting on a maintenance schedule. Silicone check discs and engineered plastic seats handle the sealing.