Those type VB's for that use would not be approved in Illinois. Not a high enough safety rating. Have not looked up the specs for a Bidet in a while.
Most similar I can think of would be an aspirator in funeral parlor pre area. You may have an atmospheric in line with no control valve after the VB, mounted 7' above the floor. The control valve would be flush or wall mounted below at hand height and before the VB
If it's not a testable backflow do you ever know that it is really safe and working properly?
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