I don't do doo, so we train ours to use the "zone" way out back. About a 100 sq. ft. area that we just don't use!!! 30 minutes after feeding, put 'em on the leash and head out to the zone. Only takes about 3 weeks to get them in the habit. We did it with our Cairn, the Keeshond and the Lab. My burn pit is there and an occasional shovelful of ash takes care of any lingering problems that the sprinkler system doesn't.
