Because it was designed for an irrigation system, which in almost any part of the US is required to be behind a backflow device of some kind. Again, there isn’t anything in the ABS material that is going to harm you upstream from the sensor in your house. In many cases certifications like this are just a fee (and a hefty one at that) that companies pay a third party agency like NSF to certify their product. Could it be certified? Most likely, but no need for Rachio to pay the outrageous rates for something that isn’t really designed to be used on a potable water system.
