We are on septic, plus have hardpan. Funny thing is that it property drains so well that even though the water company knows there is a leak in the line on their side of the water meter, they can't find it anymore. The idiots building next door got it last winter, and as soon as it got covered up it disappeared. The one dude from the water company said they'd be able to find it cuz it would bubble up, I said no you won't. In the middle of our unusually cold and frozen winter it was liquid the whole time, and there water was draining at the same rate as the leak, so the deepest the water ever got was 8 inches. You could even see the water moving.