| You can have them, or yourself, run the 4" PVC pipe under the gravel base and cap off where the drain would be located. You can then come back later and chip out the thin concrete over the drain cap and install grate. I am in the middle of a garage/house addition and that's what we are doing to get around the codes. The drain pipe is going through a 6" sleeve in the foundation wall and will be run under ground and tied in with the gutter down spouts that daylight around 60' from the house.
There are other ways to get around the codes, but don't try to tiy them in to the sewer system. That's where they get really picky so you can't dump oil or gas in the sewer.
Nice layout by the way!!! |