Some brown smooth flat plastic-like debris has appeared in my hot water line. It has been plugging my faucets and shower heads thus slowing the water flow. I have an Amtrol Boilermate and was wondering if it could be some inner lining that has deteriorated. I've never seen hard-water mineral deposits like this before. I have done repeated flushes on my lines at a number of the faucets. Any thoughts of what it could be and the possible fix?