Watts 0559121 1 IN Lead Free Thermostatic Mixing Valve with Solder Union End Connections, Adjustable Out 80-120 F

All three ports on the Watts LFMMV 0559121 are 1 inch solder socket, hot inlet, cold inlet, and outlet, and they come as union ends so the valve body can be pulled without cutting the copper. Sweat them to 1 inch type L or M copper. There is no threaded option on this model, the thread type fields are not applicable, so if your rough-in is NPT you will need adapters or a threaded version of the valve instead.

Yes. The adjustable range is 80 to 120 degrees F, and the valve leaves the factory set at 105 F, so 120 F is the top of its range. Outlet accuracy is plus or minus 7 degrees F, which is worth knowing if you are trying to hold a tight setpoint for a code-required maximum, since at a 120 setting the delivered water can land above or below that band.

Flow range is 0.5 to 20 GPM, with rated capacity of 20 GPM at 125 PSI. The 0.5 GPM low end matters as much as the top: it will still regulate on a single low-flow lavatory, so it works for a point-of-use application as well as a small multi-fixture group off a water heater. Size your branch so peak demand stays under 20 GPM.

Hot inlet needs to be between 120 and 180 degrees F, and the hot supply has to run at least 5 degrees F above your outlet setpoint for the thermostatic element to control. Cold inlet is rated 39 to 85 degrees F. If you are storing at 140 F and mixing down to 120, you are well inside that window. A tank set at 115 will not give you stable 120 at the fixture.

The body is a lead free copper silicon alloy with a rough bronze finish, which is what makes it acceptable on potable domestic water lines rather than only on heating loops.

No cold water bypass on this one. Everything passing through the outlet is tempered by the thermostatic element, so you cannot draw unmixed cold through the valve. If your design needs a bypass, for high-volume cold draw or a specific code-required arrangement, you need a different model.

Its control band is plus or minus 7 degrees F against an adjustable 80 to 120 F range, which is a general-service tolerance rather than the tight control an emergency fixture or an anti-scald point-of-use application usually calls for. Use it for tempering hot water distribution off a heater; for a dedicated emergency eyewash or safety shower, specify a valve built for that duty.

Order Watts 559121, the 1 inch LFMMV series thermostatic mixing valve with solder union ends. It is also written as 0559121. Before swapping, check that the valve coming out is also 1 inch sweat rather than threaded, since the connection style is not interchangeable without adapters.

Yes, the outlet is listed as 25 MM, which is the 1 inch nominal copper size. Hot and cold inlets match at 1 inch. Note these are solder sockets for inch-size North American copper tube, not metric OD tube, so confirm the pipe on site before sweating.