Check valve installation must always be performed by a licensed and certified backflow testing company, as per state and federal law.  For those uninformed, there is no wiggle-room in this statement.

Check valves guarantee that your water will flow in the correct direction, and should backflow, or flow-reversal occur, the check valve is designed to automatically shut down the flow of that water, thus insuring that contaminated water does not make its way into the potable water supply.

For the best in affordable backflow testing, City Backflow Testing is the name to call in the State of Texas.