B.10 - Inverted Siphons.

The use of inverted siphons is discouraged due to high maintenance requirements and will not be allowed on collector lines. A minimum of two flow barrels is allowed for a new inverted siphon for substantial existing flows. A minimum of three flow barrels is required when initial flows are substantially lower than future flows. The inverted siphon shall have an air flow barrel between the siphon inlet and outlet structures with a minimum size of one-half the diameter of the upstream pipe. The air jumper design shall provide for removal of condensation.

The smallest barrel should have a minimum velocity of 3.0 ft/sec at initial Peak Dry Weather Flow. The complete inverted siphon shall have capacity for future Peak Wet Weather Flow. Under all flow conditions the siphon should be designed so that head loss does not cause backwater or surcharging in the upstream sewer. Engineering calculations shall be submitted showing the head, flow, and velocity for each barrel at initial and future design flows.

The siphon inlet and outlet structures should be located with convenient access. Weirs at the siphon inlet to control flow splits between barrels shall have provisions for height adjustment. The siphon outlet structure should be designed to facilitate hydraulic and mechanical cleaning of the siphon barrels. The pipe profiles shall be designed with smooth curves to allow passage of cleaning equipment. Corrosion resistant materials and coatings shall be used for inverted siphon structures and pipes.

(Ord. No. 2016-61, § 1(Exh. A), 10-13-16)