I've been asked about putting recesses in the slab under various water-using fixtures (sink, DW, clothes washer, etc.) that would contain and drain any leaks from the fixture. Since I use site-built and finished wood floors in a lot of my kitchens, this is an appealing safety net, but I'm not sure of what the best way is to do it. I'm reluctant to simply pipe the drain to the side of the slab and have it exit above grade, as the opening would allow air leakage as well as provide a nice way into the house for bugs. Alternatively, if I hook it up to the sewer line, I'd imagine that the p-trap would eventually dry out and I'd get sewer gas coming up from under the fixtures. Is there a good way to accomplish this otherwise very logical detail without the aforementioned issues being a problem?