I think if you have a septic system, people are concerned that might be a problem, but I always wash my rag quilts in my machine. I would feel really bad if I messed up a machine at the laundromat. I have never had a problem. My machine drains out into our back yard. This method is called gray water because I believe laundry detergent is not harmful to the environment. I checked the pipe after my first rag quilt and there were a lot of threads, but it didn't clog the pipe. It is certainly more convenient to wash them at home.