Many people have happened to return to the boat after a period of absence and experience a rotten smell when the taps are turned on and the first fresh water comes out. The exhalation is much more pronounced and pungent when reusing the toilet after even a short stop and ends up lingeringly soaking the toilet area.
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Fresh water by boat. Why does it smell?
Such phenomena do not occur in homes, even when returning after the summer vacation; tap water does not stink, much less the toilet.
The reason for these odors is due to the different types of materials used in the two plumbing systems: In homes, the pipes are made of metal or black hard plastic embedded in concrete and thus completely insulated from light, while in most boats they are made of transparent soft plastic material that thus allows light to pass through. In addition, such materials (e.g., PVC) are partially gas permeable, allowing odors to escape and absorb oxygen from the air, increasing fermentation processes.
It is the light that contributes to the growth of bacteria, mold and algae inside the tubes, aided by the poor passage of water due to both occasional use and the slower rate of water flow, and helped in the toilet area by the encrustations that form inside the pipes over time (see the drawing above).
Fresh water and odors, how to eliminate them
A first solution is to disinfect tank water by adding amuchin, vinegar or other substances. Some improvement is achieved with the reduction of miasmas, but not their disappearance. This method is not applicable, for obvious reasons, to toilet pipes. The solution is to use, instead of porous and transparent plastic pipes, those made of colored rigid plastic material (the best color is black), which are opaque to light and impermeable to gases and odors.
Of course, this is not always possible-it has to be anticipated when the boat is under construction because it requires design engineering that not all boatyards are capable of. Replacing soft, clear hoses with hard ones is often a tricky business: an excellent alternative (especially for freshwater hoses) is to replace the soft hoses with new soft ones (so clean inside) and sheath them in the hoses used for electrical cables. This will prevent the passage of light and thus prevent bacterial growth.
For toilet pipes, there are commercially available soft ones armed with a white “odor-proof” color, which reduce perspiration and the typical pungent odor. It is better still to use black hard plastic pipes: their installation is certainly more laborious, but the end result is the disappearance of all odors.
In the toilet: a trick
When leaving the boat for some time, pour half a liter of natural mineral water into the toilet and pump it out.
Thus, the liquid that remains inside is free of the bacterial load present in seawater (very strong in harbors) and bacterial growth will be slowed. The use of chemicals for the on-board toilet is inadvisable: deterioration could occur with foreseeable degradation of the rubbers and pump seals and unpleasant consequences.
