Saltwater and uric acid (don’t ask!) produce calcium scale inside a marine head and discharge hoses. Such deposits cause the toilet to get progressively harder to flush and can lead to total blockage. Avoid this unpleasantry by pouring a pint of white vinegar into the bowl once a month and pumping it slowly — a single stroke every 4 or 5 minutes — through the head. The mildly acidic vinegar dissolves fresh scale deposits.

To keep the pump operating smoothly, follow the vinegar treatment with an ounce or two of mineral oil or a lubricant specifically formulated for a marine head.