peration. Relative ease of installation. Relatively low equipment and maintenance costs. Disadvantages: Users must flush wasted from bowl using a manual pump. Electric toiletsAdvantages: Ease of use. Typically macerate solid wastes, reducing the possibility of clogged waste lines. Macerated solid wasted are more effectively treated by disinfectants and deodorants. Relatively easy to interface with a Type I or II MSD for automatic treatment. Disadvantages: Rely on electric power for flushing action. Manual backup, if provided, will permit system use if power is depleted or there is a malfunction. More complex to install; higher cost. Vacuum toiletsAdvantages: Ease of use. Typically use less than a quart of water per flush, a real benefit for optimizing holding tank capacity. Disadvantages: Require electric to operate. While seawater is most often used for flushing, some electric and vacuum systems recommend fresh water. TanksThe size of the holding tank selected should be based on the boat's intended usage (day trips, weekend or extended cruises, etc.) and the number of people using the toilet. Some experts have estimated that the average effluent (sewage and flushing water) per person per day may be as low as three gallons; in many cases it will be higher. Leakage typically occurs at fill, pump-out and vent line connections. The more flexible the tank, the more difficult it is to maintain leak-free connections. Connection sites on a flexible tank must be reinforced to minimize the deformation of mating surfaces. Plastic (polyethylene) tanks are rotationally molded and, therefore, have no seams. They typically have a wall thickness of 1/8, 1/4 or 3/8 inch. Wall thickness is a key to a tanks structural rigidity and resistance to odor permeation. Odor permeation is more likely to occur in tanks with a wall thickness under 1/4". Thicker...
