I used an 8 1/2 foot sink that I made for about 17 years. I used a drop of a little less than 1/16” figuring that water flows off of level. I had the drain in the back corner even though the plumbing drain was below the center of the sink on the wall. I ran a drain pipe from the sink drain into a trap then into the main drain. The only place that I had any issues with dampness was in the corner where the drain was placed since the drain was round and the sink was not.
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