(1) When piping within secondary containment or an operational area is directly connected to a water source such as a well or public water system, an approved air gap or an approved reduced pressure principle backflow prevention assembly (RPBA) shall be installed to protect the water source. Approved air gaps and approved RPBA's shall be installed, operated, inspected and/or tested and maintained per WAC 246-290-490.

(2) Approved RPBA's shall be inspected and tested by a Washington state department of health certified backflow assembly tester, and approved air gaps shall be inspected by a Washington state department of health certified backflow assembly tester or cross-connection control specialist[:]

[(a)] At the time of installation, alteration or relocation, and at least on an annual schedule thereafter.