I plan on having a composting toilet put inside my homestead, so this would be only for grey water discharge. I was wondering if anyone has ever ran all of their gray water through a 4″ PVC pipe that discharges below the frost line into a trench. I would have the pipe buried 4’deep with a trench 3′ wide×4′ deep×10′-12′ long, covered in gravel, and possibly have some sort of insulated enclosure covering the top of the trench. I’d install a polypropylene box of some sort with a filter trap that the end of the discharge pipe enters into, with an access lid to be able to clean out the filter trap occasionally.  This box would have an insulated enclosure built over it. I’d have filter screens over the washing machine discharge, kitchen sink trap, and dishwasher. I would also install a trap in the house near the outside in the event I had to clean the pipe with a roto rooter. So there should be very little heavy particulates heading towards the outside discharge pipe. I figure most of the fats and grease would gather in the filter of the polypropylene box, and mostly grey water would enter the trench once it leaves the box. The ground on the property is mostly shale and drains quickly. The well depth is at least 300′ deep, so with just Grey water with only liquid soaps/ detergents being discharged, I should be without fear of ground water contamination, right? Or should I worry? The property is in a rural area here in Montana. There are no covenants. There will be no permits. I was wondering if anyone has done, or knows of anyone who has done this without going with an actual grey water settling tank. Thanks for your thoughts.