How do you choose the right equipment for your boat?
dump at the pump




warningCaution: Before making your final equipment selections, read the section on "Installation Tips." Installation considerations may affect specific equipment choices.


The type of toilet selected depends largely on the boats size and electrical power supply as well as the owner's budget.

Caution: Seacocks at seawater intake and overboard discharge through-hulls should be closed whenever the boat is not in use...regardless of the type of toilet selected.

Manually operated toilets


  • Not dependent on power source.
  • Dependable operation.
  • Relative ease of installation.
  • Relatively low equipment and maintenance costs.


  • Users must flush wasted from bowl using a manual pump.

Electric toilets


  • 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.


  • 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 toilets:


  • Ease of use.
  • Typically use less than a quart of water per flush, a real benefit for optimizing holding tank capacity.


  • Require electric to operate.

While seawater is most often used for flushing, some electric and vacuum systems recommend fresh water.

Caution: Flush water plumbing must be arranged to prevent contamination of the boat's portable fresh water supply (refer to ABYC standard H-23, Installation of Potable Water System).





The 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, pumpout 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.