A property has a private well that is interconnected with, or could be cross-connected to, the public water supply. Under Washington's cross-connection rules (which the UPC defers to), what protection is required at the connection to the public system?
Not quite. The answer is C: A reduced pressure principle (RP) backflow preventer or an approved air gap
Washington's Department of Health rules class a premises with an unapproved auxiliary water supply interconnected with the potable supply as a high health hazard, and require premises isolation by an approved air gap or a reduced-pressure principle backflow assembly. A check valve alone can fail silently, a sign relies on someone obeying it, and capping the well when not in use does not remove the hazard. The UPC's chapter 6 requires its backflow devices to be models approved by the Department of Health and points back to this rule.
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