Above ground backflow valve info.

Above ground back flow valves are required for many states and community's.  They work as a double redundant emergency shut off.  This allows the sprinkler system owner to shut off the water to the sprinkler system, but maintain the water to the home or business.  (example) A sprinkler zone may be running constantly, not shutting off.  One of the sprinkler valves may be stuck open.  The home owner can go to the above ground back flow valve, turn one of the two shutoff handles and shut off the water to the sprinkler system.  Then a sprinkler repair company can be called to fix or replace the valve.  In other words, if you need to turn of the water to your sprinkler system manually, go the the above ground back flow valve and turn one of the handles.

PROBLEM WITH ABOVE GROUND BACK FLOW VALVE.  The fittings for a Back Flow Valve are Brass.  They freeze and break easily!  Water will shoot out.  Depending on what part of the back flow valve freezes and breaks determines if turning one of the valves will shut off the water.  There are many different steps that can be taken to keep an above ground back flow valve from freezing.  What can or can't be done to prevent the valve from freezing is determined by your city and state code.  The codes vary widely.