I am looking at finally burying the downspouts at my house. I have been told to go 4" PVC hard pipe. The problem is, with the terrain on the north end of my house, I would need to then dig down pretty far to get a constant sloping, un-undulating line from the house to the terminus. Plus, that would be tons more $$ compared to a roll of the drainage tile/pipe. Those who have done this, is flexible drain tile ok? I was told to wrap flexible tile with weed/landscape matting so the soil doesn't get into the perforations of the tile and block up the pipe. How deep would you dig to lay the drain pipe in an area that freezes hard in winter? I am going the easy route and rent both a sodcutter and a trencher, as I don't want to deal with seeding and watering again, and as the glaciers stopped right in my backyard, there are tons of rock here that I don't want to use a shovel vs trencher. Any tips or advice before I tackle this is highly appreciated.