Thanks, Gerry. It all makes sense ... thanks. I was just trying to avoid putting in an overflow box -- lazy. Running the sump all along the back is an interesting idea. I did find one example on the internet of a sump in the middle of the back. Here is a top view of what I found:



It looks pretty nice. I think it was 6" on the angled lengths and 12" on the long length for a total of 24" of overflow. In this example, the builder always puts 2 drains in his tanks in case one gets clogged. So, there were 2 drains in this overflow.