The answer to 'why is my backflow preventer rusty water' is that a rusty backflow preventer is often caused by corrosion or mineral buildup inside the device. This can happen over time as the metal parts of the backflow preventer are exposed to water, air, and other environmental factors. The rust can discolor the water coming out of the backflow preventer, making it appear reddish or brownish.
Some common causes of a rusty backflow preventer include old age, poor water quality, and lack of maintenance. If the backflow preventer is not serviced regularly, the internal components can start to deteriorate and corrode, leading to the rusty water issue. In some cases, the backflow preventer may need to be replaced if the damage is severe.