WAC 246-291-210. Distribution systems

(1) Storage reservoirs shall be designed to: (a) Prevent entry by birds, animals, insects, excessive dust, and other potential sources of external contamination; (b) Include: (i) A weathertight roof; (ii) A lockable access hatch; (iii) A screened roof vent; (iv) An overflow pipe with atmospheric discharge or other suitable means to prevent a cross-connection; (v) A sample tap; (vi) A drain to daylight, or an alternative design approved by the department or health officer that is adequate to protect against cross-connection; (vii) Tank isolation in order to perform maintenance procedures; and (viii) Other appurtenances appropriate for the protection of stored water from contamination; (c) Be above normal ground surface level. If the bottom elevation of a storage reservoir must be below normal ground surface: (i) The storage reservoir must be placed above the groundwater table; and (ii) The top of a partially buried storage reservoir must be at least two feet above normal ground surface. (2) A Group B system designed to supply fire hydrants must have a minimum distribution main size of six inches (150 mm) supplying each hydrant.