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- Oct 13, 2016
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Here's the problem: The water entering the internal box at the weir has to fall too far to the water level in the overflow. It's about 3/4" from the midpoint of the weir openings down to the top of the external box. You really ought to have about 1/2" from the top of the box to the top of your emergency drain (Bean Animal). I tried 1/4", but with a lot of flow you need some headroom for water to overflow the top and there's quite a bit of turbulence and waves. Maybe it would be OK with only 1/4" with the lid snapped on, but see below. Your open channel should probably be at least 1/4" below your emergency. This gives at least 1-1/2" drop which can be noisy. Another complication is that if you use the U pipe at the top of your open channel stand pipe, it's top will be about 2" above the water level, which will put it above the top of the external box and the lid won't go on. If you shorten your open channel stand pipe, you either have to have a lot of flow in your open channel, or the drop increases to about 2-1/2".