I have said many nasty words about this...
Take a look at the tank shape in this post
. On reflection, the drain/source at the center of the tank makes some sense--the pickup was curved down against the bottom of the tank, so it really did suck out most of the water in the tank. I guess it made [some] sense to drain it here, too.
But I would much rather have had a tank that was installed with a sloped bottom toward the street side and drain from that side, too.
You can see how I modified the tank in post #73
in the same thread. This hasn't been installed and tested yet, mostly because I was waiting for warm weather so I could POR-15 the frame. That should happen next month (it's been snowing for the last 4 days here). I'm going to devise a sloped layer of insulation under the tank to ensure good drainage to the street side.