Portapotties require no plumbing; they may or may not have a reservoir for flush water. Bowl contents drain by gravity into a removable tank which is carried off the boat and dumped, although some larger models can be fitted for pumpout. Very little water is used in the operation. Capacity is 10 – 25 litres.
The Heads (Marine Toilet)
Manual pump heads are just what the name implies: you pump water in and out of the bowl manually. They are designed to use “raw” (sea, lake or river) water for flushing. The amount of flush water can be controlled to some extent by how much you pump.. It is possible to add an electric motor (typically 12v DC current) to some models; the motor simply replaces your arm in activating the pump.
Electric macerating heads are only a little more complex than a manual head. They are typically designed to use raw water. An impeller pump replaces the piston type found in manual heads, and there is also a discharge pump. Between the two is a device called macerator that is not totally unlike a blender or a garbage disposal, it purees solid waste & paper. Like a garbage disposal, a macerating head needs a lot of water, typically 1 to 3 gallons each time it is flushed, or it will burn out.
Sanitation hose has long been the subject of a whole lot of debate. Some experts insist that anything less than double walled hose is unacceptable, some even recommend the use of rigid PVC. In fact, the first is an unnecessary expense, the second could be the worst thing you could do.
There have been problems with the hose in the past, and there is a hose on the market today that is totally unsuitable for sewage and it is impossible to determine, just by looking, whether a particular white flexible PVC hose is suitable for use in sanitation systems or not. Vela tanks can supply a sanitation grade hose.
Finally, the system, including the tank, should be at least nominally rinsed after each pump-out through the head or back down the deck pump-out with fresh water only.
Never put anything into a marine sanitation system that is not specifically marketed for that purpose. Do not use detergent, washing up liquid or other cleaners, especially cleaning products which contain pine oil, petroleum, or alcohol. Those substances will break down the seals, gaskets, and valves in the system, and will also break down the walls of the hose, causing it to be more susceptible to permeation. Above all, do not pour vegetable oil down the head to “lubricate” the parts. A layer of oil on the sewage will only seal the contents of the tank, keeping air out of it. Follow manufacturers’ recommendations for periodic maintenance and lubrication.
At least once every two years put a complete rebuild kit in your head as part of your regular spring recommissioning; if you lay your boat up every winter, we suggest doing it every year. When seals, gaskets, valves and impellers dry out they become brittle and prone to crack. By replacing them regularly you all but eliminate the possibility that you will have to make emergency repairs to the head. Although it is impossible to predict someone putting something in the head that is too large to pass through, a well-sealed pump working to factory specifications can often push a borderline object through that a worn system cannot. “Do not put anything into the head that hasn’t been eaten first!” Marine toilet paper, if available at all, is a poor solution. Just don’t put anything else in the head.
Dr. Yusuf Civelekoglu, CMI