Our small apartment building in Queens, NY, was built in 1915 and has cast iron waste pipes. We recently had to replace a length of pipe under one apartment, and the metal had become paper-thin on the bottom. We suspect that the tenant's washing machine might have exacerbated the damage. Should we ban washing machines? What about dish washers? Is there a brand or kind of detergent that will minimize damage to our aging pipes? We've warned tenants not to use harsh drain cleaners, but what about the chemicals we use daily? Any advice would be appreciated!