Usually 15 to 30 yards from the house or building. Look for depressions were the ground may have settled over them & use a metal rod to probe the area. Unexpected vegetation may occur over the fertilized area. Also look around trees, some were put there for shade & privacy.
There are no (average) distance to put a privy people did weird things back then like they do today, some people put them far away because of the stink, some didn't want to run the 30 yard dash at night and put them close, I have found privies right out side the back door, and at the very end of the yard, some on the side of the house, but when you do row homes they seem to be all in a line, like they built them all around the same time, I just probe every sink hole, and if i still cant find it then I probe the whole yard in 2 foot streachs.Rick
Up here in Maine country I have found that many times the trash was dumped over and into the nearest gully, ditch, riverbank,etc, some dumps were right next to the barn if it was built on or near a slope, sometimes it was a five minute walk over the pasture to the edge of the nearest dropoff. I've also found quite a few dumps under the ell or summer kitchen which usually did not have a foundation, but a crawlspace under it. They would just lift a floorboard or something and toss trash under it onto the ground. Anyway, you've got to look around the site and think with an " out of site, out of mind" mentality regarding trash disposal. I also will walk the perimeter of pastures, follow stone walls, and meander up and down brooks or riverbanks to find dumps. That usually works for me, as long as I have my deet! That's wicked good bug spray round heah.