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First, I have assessed potential solutions which utilize multiple 2-inch gate valves to avoid using the larger, more expensive valves. Cost analysis has shown that this is only feasible for a 3-inch flow control pipe, with 2 2-inch valves/pipes feeding in. Larger diameters require too many valves and fittings to increase the cost, and are less friendly for the operator.
Since, I have assessed another alternative design for the entrance tank that features the use of one or more Fernco flexible fittings as an "adjustable weir" configuration on the drain stopper pipes. This design is clearly more cost effective than any of the previous considerations.
Spring 2014 Contributions
I am currently working with Runpeng Yu on fine-tuning the new alternative design for entrance tank flow control featuring Fernco flexible fittings on the drain stopper pipes, and coding in Mathcad so that this design can be reflected on the design server.