Re: shower sump maintenance
Bleach will disinfect it to an extent but it won't clean it or reduce the scum. Undiluted bleach will attack rubber parts in the pump so don't use any more than necessary. Where does the grey water go from the sump? Overboard? If so, you may be able to route grey water from the sinks and AC directly overboard and have only the shower (if equipped) water enter the sump. My boat has two sinks, one on each side, each with its own through hull. There are a few boating areas where this is not permitted, all grey water must be collected and disposed of on shore. Most areas allow grey water to be discharged overboard.
