A sewage backflow preventer does exactly what the name implies: it prevents sewage from backing up and entering your basement, garage, or home.  It performs this task using some sort of valve, or a series of valves, which sense when the flow has reversed and automatically shuts down that flow until normalcy is restored. To

The Watts Backflow Preventer 009 is a reduced pressure zone assembly designed to prevent the reverse flow of polluted water from entering the potable water supply. This is caused, in most cases, by backflow, back-pressure, or back-siphonage, and the only thing that can prevent this polluted water from entering the water supply is a backflow

An irrigation check valve is your answer for those annoying puddling situations in your irrigation system.  Any irrigation system requires ups and downs to fit the landscape, and water will always seek out the lowest points in an irrigation system when that system is at rest.  An irrigation check valve prevents this unsightly puddling from