I understand why you would clog up stuff in the septic tank but what happens to the threads in a laundramat? do you just clog up the city water works plant?
Also if you give the rag quilt away, do you tell the new owner how to wash it safely? Or ask if they have a septic tank? Just wondering.

When I make a Rag Quilt, I always put it in a large calico bag so that any loose threads stay wihtin the bag. When you take the quilt out of the bag after it has been washed you just have to give it a good shake outside and the threads simply shake off. Just amke sue you do this OUTSIDE!!! Good luck!