Watts 0792039 3/4 In Lead Free Anti-Siphon Vacuum Breaker Backflow Preventer

Both ends of the Watts LF288A anti-siphon vacuum breaker are 3/4 inch female NPT, inlet and outlet alike. So it threads directly onto a 3/4 inch male NPT nipple or male-threaded outlet on the supply side, and takes a male NPT fitting downstream. If the pipe you are tying into is copper, PEX, or male hose thread rather than 3/4 NPT, you need an adapter to get to male NPT first.

No. The LF288A is a non-continuous pressure device, which is the defining limit on an atmospheric vacuum breaker: it can only sit under line pressure intermittently, and it must not have a shutoff valve, solenoid, or any closed valve downstream of it holding pressure against the poppet. Typical use is immediately downstream of the last control valve. If your application keeps the device pressurized for more than about twelve hours at a stretch, or has a valve after it, you need a pressure vacuum breaker or an RPZ instead, not this one.

The body is lead free brass, which is what makes it legal on potable water lines under the federal lead-free rule for pipe and fittings in contact with drinking water. Seat and disc are silicone. Nothing in the wetted path is a plated leaded-brass part.

It is rated for health hazard (high hazard) backsiphonage protection, so it covers connections where what could be siphoned back is toxic, not just objectionable. That means chemical injectors, sprayers, mop sinks, and irrigation zones with fertilizer are within its hazard class. Note that it protects against backsiphonage only, not backpressure, so a system that can push contaminated water back toward the main under its own pressure needs a different device.

The LF288A is a non-testable device. There are no test cocks on it and no annual test procedure to schedule; when it fails you replace it rather than rebuild and recertify. For facilities that carry an annual backflow test program, that is the practical difference between this and a testable assembly such as a double check or an RPZ, which do require a certified tester every year.

Rated to 180 degrees F (82 C) maximum and 125 psi (8.6 bar) maximum working pressure, with a 33 degree F (0.5 C) minimum. That covers ordinary domestic hot water service, but it is not built for hot and harsh water duty, so continuous high-temperature or aggressive water applications are outside what it is rated for. Also worth checking your static line pressure: if the building runs above 125 psi you need a pressure reducing valve ahead of it.

Neither is included. The LF288A has no inlet shutoff and no outlet shutoff, and no strainer. If your install needs isolation for service you are piping in your own ball valves, and remember the valve arrangement matters here: this is a non-continuous pressure device, so a shutoff belongs upstream, not downstream where it would hold pressure on the breaker. There is also no bypass, no meter, no elbow fitting, and no cap and tether on the assembly.

It comes down to where the device sits relative to the control valves. An atmospheric anti-siphon vacuum breaker like the Watts LF288A goes downstream of the last valve, one per zone, and can only be pressurized intermittently. A pressure vacuum breaker sits upstream of all the zone valves, holds pressure continuously, and covers the whole system with one device. If you have several zones and want a single point of protection ahead of the manifold, the LF288A is the wrong architecture. If each zone valve needs its own breaker on the discharge side, this is the type you want.

792039 is the manufacturer part number for the 3/4 inch lead free unit in the Watts LF288A series, so a spec calling out either the LF288A at 3/4 inch or Watts 792039 lands on the same device. For a property standardizing across multiple openings or hose connections, that MPN is the one to put on the requisition; the size is fixed at 3/4 inch NPT on both ends.

Its rated minimum is 33 degrees F, which is above freezing, so it is not a freeze-tolerant device. Outdoors in a climate that drops below freezing it needs to be drained down for the winter or installed where it stays above that minimum. Brass bodies split when water in them freezes, and the atmospheric port on a vacuum breaker will not drain the body for you.

The 3/4 inch inlet and outlet correspond to 20 mm nominal, but the threads are NPT, not BSP. On a metric system built with BSP parallel or taper threads, NPT will not seal properly even though the nominal size lines up. You need an NPT to BSP adapter at each end.