This Watts 386473 (B9-11TM3) combination unit pairs a Model 1156F feed water pressure regulator with a Model 9D dual-check backflow preventer in one bronze body built specifically for press-fit installation. It automatically feeds make-up water to a hydronic boiler whenever system pressure drops below its setting, while the built-in vent stops that boiler water from ever siphoning back into your potable supply line. Plumbing Supply And More carries this exact press-connection variant for contractors who need to close out a boiler feed job without firing up a torch. This Watts Backflow Preventer Uses Press Connections Instead of Solder Most listings for Watts' Series 911 combination valve bury the connection type as an afterthought. On this particular model, it's the whole point. The 386473 ships with 1/2" Viega ProPress-compatible press ends instead of the sweat or threaded unions found on other 911-series variants. That means a technician can crimp it into copper tubing with a press tool and have a sealed, tested connection in seconds, with no open flame near an occupied mechanical room, no cool-down wait before pressure testing, and no risk of scorching nearby wiring or insulation during a retrofit. For jobs where a torch simply isn't practical, an occupied basement, a tight mechanical closet, a system that needs to be back online the same day, this is the variant that gets specified instead of the solder or NPT versions of the same 1156F-9D combination. How This Backflow Preventer & Feed Regulator Work Together This unit is really two separate Watts devices pre-assembled into a single bronze body. The Model 1156F is a feed water pressure regulator: it senses system pressure on the boiler side and opens to admit make-up water only when that pressure falls below its set point, then closes once the system is back up to pressure. The Model 9D is a dual-check backflow preventer with an atmospheric vent sitting just downstream of the regulator. Under normal operation, incoming supply pressure holds the 9D's internal checks closed against the vent. If supply pressure ever drops to zero, or if boiler-side pressure tries to push backward through the line (backsiphonage), the vent opens and discharges that water to atmosphere rather than letting it travel back into the building's potable piping. That open-air discharge path is what makes this a non-testable, vent-style backflow preventer rather than a reduced-pressure zone assembly, and it's why local code officials generally accept it specifically for boiler feed applications rather than for a full potable-water cross-connection. Pressure Settings, Ratings & Temperature Limits Watts documentation for the 1156F regulator lists an adjustable range of 10 to 25 PSI, with the valve factory-set at 15 PSI out of the box. The combination unit carries a maximum working pressure of 100 PSI and a maximum operating temperature of 212°F, which covers the hot water side of essentially any residential or light commercial hydronic boiler loop. Factory pressure setting: 15 PSI / 1 bar (field-adjustable from 10 to 25 PSI, or 0.7 to 1.7 bar) Maximum working pressure: 100 PSI / 6.9 bar Maximum fluid temperature: 212°F / 100°C Connections: 1/2" press x press Body material: bronze, Buy American Act compliant If your system's static fill pressure needs to sit above 25 PSI, this is the wrong valve for the job. Confirm your target fill pressure against your boiler manufacturer's fill chart before ordering. Can You Use This Valve On a Drinking Water Line? No, and this is worth stating plainly instead of leaving it in fine print. Watts' own product data lists this SKU as not lead-free under the Safe Drinking Water Act's low-lead standard, which means it's rated for non-potable boiler feed water only, never for a line that supplies drinking or cooking water. That restriction doesn't affect its intended job. A boiler feed line isn't a drinking water fixture, and the whole reason the 9D preventer exists is to keep that boiler-side water separated from the potable supply upstream of it. Just don't repurpose this exact part number anywhere downstream of a kitchen or bathroom fixture. Why Does the Vent Need to Face Open Air on This Model? This combination valve installs in either a horizontal or vertical run, which gives more flexibility
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