We live in a 1996 mobile home and there has been black gunk building up in the faucet screens and in the toilets (both tank and bowl). Also when we wash our clothes it initially smells like rotten eggs. We are on public water, and no one else has this problem. The pipes are pvc and obviously not that old. I heard it might be our hot water heater but why would that cause the black gunk in the toilets? Any help would be appreciated. Thanks