There is nothing that nautical technicians hate more than fixing heads. I actually know of some companies that have a surcharge for dealing with these problems. I was on a technical course a few years ago about a particular marine toilet system, the very first thing that was discussed was health & safety. The number of vaccinations you should be up to date with and the number of nasties you can catch is terrible.
If you are working on these systems in your boat, even if it is only you who has used it, remember, gloves, mask and disinfectant. The toilet system on a boat is also known as the black water system, Water, water everywhere. Water on board a boat.
Why head?
Head is a centuries old nautical term, it means the very front of the ship where typically the toilet was located, the idea being that the water moving around as the ship moves would keep the area clean.
All marine heads require water, either salt or fresh.
Fresh water flush uses water from the tank to work, the benefit is "odd" smells are rare, unless the water in the supplying tank is not very fresh. It also means one less thru hull fitting needs to be installed. The downside, it uses fresh water so, no water in the tank, no toilet flush. There is the consideration of using an unnecessary amount of fresh water too, however little.
Salt water systems use sea water (or lake water) sucked up from the bottom of the boat to be used for flushing the toilet. These types are the more common on the two, they require two thru hull fittings, one for inlet and one for outlet. If left unused for long periods, they develop a funky odor, nothing to do with toilet or bodily waste, more that sea water contains micro organisms, these get trapped in the inlet pipes, decompose and make those smells, they also can discolor the toilet bowl.
What not to do
Unlike your home sewage pipes, the ones on a boat are much narrower, something of the order of 1 1/2" (38mm), the ones at home are over 4", around 110mm, they can get blocked easily some rules are ignored.
Toilet paper, use the minimum possible, buy either the special biodegradable type for boats and caravans or the cheap supermarket stuff so it breaks up easily, the expensive quilted type is not recommended.
No wet wipes, make up wipes, sanitary products shall be put down the toilet, apart from being very difficult to break down, they cause havoc with electric toilets, they will get stuck in the blades and various valves.
The basic rule of thumb is if it is something that has not passed through the body, avoid flushing it down the toilet.
Tanked up
Depending upon the age and often the country of origin of the boat, it may have a tank (black water or holding tank) for toilet waste. Some systems have a diverter valve to choose between waste going to the tank or directly overboard. You may find if you buy an older boat a black water tank will be a requirement in order to navigate under certain countries flags of registration and you will have to fit a tank.
Three common ways for emptying the holding tank;
Deck fitting, a bit like the fresh water tank or fuel filler fitting, an external pump, tank and hose are brought down to the boat, the hose inserted into the fitting and the contents of the tank sucked out.
Pump, sometimes known as a macerator (a type of pump with blades in it), it can also be another kind of pump, either way it sucks the contents of the holding tank out and expels them via a thru hull hull fitting, usually buy not always below the waterline.
Gravity, this is familiar to owners of French built vessels. The tank is mounted high up, above the height of the toilet and above the waterline, the emptying process is as easy as it gets, open a valve below the waterline and the tank contents empty, close the valve and the process is finished.
All tanks, water, fuel and holding tanks require a breather, this equalizes the pressure in the tank with atmospheric pressure as the level of liquid inside rises and falls. The breather is a hose that goes to a thru hull fitting, above the water line and above the height of the tank. In better installations, a carbon filter is installed in the breather line of the holding tank, it absorbs any smells that could waft their way across the decks.
Types of toilet Installation
Porta potti or "bucket and chuck it" as it is sometimes named. This is the most basic of systems, a two component toilet, top part is a self contained water tank, it has a plunger to pump up the pressure slightly and this is what causes the flush. The bottom part is the tank itself, when it´s full, separate the top and bottom parts, empty the tank and reinstall, very simple, a chemical catalyst is added to the bottom part to accelerate decomposition and also neutralize odours.
Manual pump. A manual handle is pumped up and down, it draws water up into the bowl, a diverter is flicked, the handle pumped again and the water is pumped out of the toilet bowl towards the holding tank or thru hull fitting. Rebuilt kits are available to do a complete overhaul of the pump. Look carefully at the price if the unit requires a full rebuild, quite a few times I have seen a new replacement pump costing very near the price of the rebuilt kit.
Electric. There are many makes but the basic premise is the same as the manual one, whereas the manual toilet has to be pumped, the electric one does the same process via the push of a button or two. Some of the high units have a button for pre and post flush, no need to maintain the button pressed for the toilet to work. There are conversion kits available for certain makes that allow the manual pump to be directly replaced by an electric unit.
Where the units differ is in the pump they use, some will have a very loud macerator unit in the base, others are equipped with a whisper quiet pump. The macerators have blades in them and so as the waste passes through them its made smaller.
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| A Vacuuflush system removed for service, the top tank and pump is the vacuum generator, the bottom tank is for black water and has the discharge pump fixed on top. |
Vacuum flush. As their name implies, these units work using vacuum pressure. A vacuum generator builds a negative pressure, when the toilet is flushed that negative pressure drags the contents of the toilet bowl towards the holding tank with the accompanying whoosh like on an airplane. There are no blades in a vacuum system, just a system of rubber valves that hold the vacuum pressure and only allow the waste to flow in one direction. Vacuum flush units are only fresh water.
Maintenance & cleaning
What can you do to keep everything working smoothly? Well, it varies a bit but some basics common to all (except maybe the porta potti).
No caustic chemicals or bleach, there are products specifically made to clean the bowl, hoses and pumps without damaging them. I have heard people using vinegar to help dissolve scale build up. Some people also use bicarbonate of soda to clean heads. Do not use the same products as at home, you could end up causing damage to the system.
Exercise the system, do not leave them idol for long periods of time, that´s what causes "odd" smells to develop and pumps to become more seized up. The thru hull valves (seacocks) should also be opened and closed to make sure they do not seize.
Long term storage, before winter up and returning the boat to the yard or storage facility, please ensure the holding tank is empty and the discharge seacock is closed. It would not be the first time that the contents of the tank have been spilt onto the boatyard floor.
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