The "Heads" or Sea Toilet
On a boat we normally call the toilet the "heads" (see "Words, words, words"). I've put a section here about it because they are usually quite different from the toilets we're used to on shore, and the time you don't want to realise that, or indeed realise you need to ask how to work it, is when you're desperate and the world is leaning over at a drunken angle. The skipper won't want that either, because it is possible, though rare, accidentally to let quite a lot of sea inside the boat.
On most boats, the toilet is quite a bit different from the type you use ashore, so whilst it's still a toilet, perhaps the different name also helps remind about the differences.
It is important to know how The Heads works. I have a page here that should help, but there's a risk of finding other types that work differently. Don't be afraid of them ... they're different, but they're not hard.
One other thought ... if on your first trip on a new boat the skipper doesn't, soon after your arrival, show how to use the heads, please ask: "How do we use the heads, please?" The most likely reason is that the skipper has just forgotten and the response will be "Ah, yes, good point". If nothing else, the same bits of different types of heads may simply be in different places from one boat to another, so the question and the answer are always important.
More than that, if you are familiar with the boat but you have a new visitor and the skipper forgets ... remind him or her to explain them. It's always easier to show and explain when on the mooring than when out on the water.
So what's different, then? ... And Why?
The first obvious difference is that there is no cistern for the flush. Most sea toilets flush with sea water that's pumped in specifically for this very flush. Usually, it will be pumped by you, though some boats do have electric flushes (that makes it sound like the menopause :-)).
You pump in the sea water to fill the toilet pan ... and it just sits there. Erm, yes, you probably have to pump it away, too. These days usually to a holding tank (black water tank), but on some older boats it still goes straight into the sea as it's done for millennia.
There is another very important part of this process. On all boats there are things called sea-cocks, which are valves or taps at the bottom of the boat that allow water into and out of pipes, and the sea-cocks are there to ensure water only come in when we want it to. If the water coming in could only ever stay within the pipe, we might no need sea-cocks, but we have them because there is always a risk that water might escape from those pipes. The pipe could get broken, or it might have an open end ... for example where it goes into the heads. I think it's safe to say that all types of heads have safety features that aim to stop that happening, but ... things can go wrong and if the heads are below water level, things could get much more exciting than most of us would want, though more likely is just a little bit of sea water sloshing around.
On many boats, standard operation is to open the sea-cocks before using the heads and close them afterwards. If those are the rules on you boat, then please do it.On some boats, the sea-cocks will be opened and closed by the skipper and you need not touch them. Check with the skipper.
OK, How Do We Use a Sea Toilet?
Generally there are common parts or functions, sometimes separated, sometimes combined. I'll try to explain a few, which hopefully will set you up so that, at the very least, when you meet one you'll understand roughly what's going on. Most have the following: Inlet sea-cock, inlet pump and output pump. Some will also have an outlet sea-cock. There are a few exceptions that I'll deal with separately, notably the LAVAC toilet and the various composting toilets, which are becoming increasingly popular. There is also that very basic for of toiulet still used in some small boats, the so-called "bucket and chuck-it", which probably needs no instructions other than don't knock it over.
Jabsco
The Jabsco Marine Toilet may be the most popular sea-toilets around at the moment. They're simple and reliable, and they're low cost. Should you have a problem with one, they're also pretty easy to take apart, clean and service.
The pump is a neat double-action arrangement and a mechanical 'switch' on the top of the pump body controls whether the pump is working "wet bowl" and simultaneously pumping water into and out of the toilet bowl, or "dry bowl", which clears the inlet ow water and pumps the toilet bowl dry.
If you're standing looking at the toilet from in front, the 'switch' to the left is "wet bowl" and to the right is "dry bowl".
To use it, the sea-cocks may need to be opened before use and closed after use, as usual.
If the bowl is dry, flick the switch to the left and pump in a little water.
Use the toilet.
After use and again facing the toilet, ensure the 'switch' is to the left and pump multiple times to flush away the waste and clean the bowl.
Once clean, flick the switch to the right and pump out any remaining water. Some skippers will then ask for a little water to be pumped into the bowl, some will not. If they do, flick the switch left, pump a few times, them flick right again.
Leave the toilet with the switch to the right, depress and twist the pump handle to the 'locked' position.
Close sea-cocks as the skipper advises.
Jabsco have some videos on their site about how the pump action works and how to maintain their toilets. I nice bit of light entertainment for those long winter evenings :-) http://jabscotech.com/
Plastimo, Force4, Dometic, etc.
These are similar to the Jabsco model. I've not used either and have yet to find instructions on-line. The skipper should know.
Blake's Classic series.
There are several in the Blake's Classic Series but they all work much the same. They're very tough and reliable as they're heavily manufactured from bronze. They're often described as "the Rolls Royce of marine toilets", though that's perhaps more a reflection of the price than anything else ... the list price for the smallest "Baby Blake" is a wallet numbing "from £4593.29" as I write. The "Victory" model is "from £6393.30". That's one reason that there are many more £200 Jabsco toilets around.
BUT ... you can find them on eBay, sometimes for the same money as a new Jabsco. Note though that the "perishable parts service kit" if/when you need them are also £170 or £222 respectively.
I have a pre-1950 "Baby" in my boat. It still works exactly as it should.
It has to be said that at first sight, that collection of Victorian-style plumbing is pretty daunting, but don't worry. It isn't really hard to use.
The Blakes toilets have two separate pumps, one for filling and one for emptying. The smaller one with the "T" handle is for filling, the larger one with the lever handle is for emptying. That larger pump comprises some heavy internal mechanicals that will macerate most stuff that goes down a toilet, though again ... Please only put down any toilet natural waste and toilet paper.
To use the toilet, there should be a little water in the bowl ... there's a line. If there isn't, open the sea-cock(s) and/or the "safety valve", the twistable valve on the top of the pump assembly. It's much like an ordinary tap ... counter-clockwise to open, clockwise to close. It's a bit comparable with the 'switch' on the Jabsco.
A couple or so pumps on the T handle should get water to the line.
Use the toilet.
You might choose to pump in more water before pumping out ... I do. Pump out with the large lever. It will normally empty the bowl in a few strokes ... it's a large pump and shifts waste much quicker than the smaller modern pumps do. Fill and empty as many times as you feel is appropriate. Pump in a little water to the line in the bowl and close sea-cocks and safety valve as the skipper advised.
That safety valve allows Blakes toilets to work safely well below the waterline, though for most boats on which we sail, that matters little.
Blake's LAVAC
The Lavac has a novel arrangement that is quite inspired, though it is held in different levels of respect, or otherwise, by different people.
The Lavac uses a seal on the underside of the seat to make the bowl airtight and then uses the output pump both to discharge the waste and to pump in fresh water. A clever valve in the water inlet pipe stops that pipe becoming a siphon and filling the boat with water.
To use the Lavac, open the sea-cocks as usual.
Use the toilet.
Close the lid and pump a few times to complete the flush.
Close the sea-cocks. And that's it.
The pumps is separate and can be mounted nearly anywhere, though it should be obvious enough.
Electric types
These are probably the closest you'll find to domestic toilets on most boats.
As far as I'm aware, just use them, close the lid and then press the 'flush' button.
As ever, put only human waste and toilet paper in them, and avoid 'wads' of the latter.
Self-Contained portables (Potra-Pottie; etc.)
Thetford Porta Potti are a small version of the things used in the portable toilets you find at outdoor public events. They have the bowl, seat and lid in the upper half and a waste container in the lower half. They are pre-charged with water and a chemical.
Use them much as a normal toilet, but the flush is done with the piston or bellows pump, top-left corner in the photograph.
The flush uses the chemical-treated water stored in the bottom half, which is recirculated.
Composting
There are two or three types of these. They all work by breaking down waste into compost, which can then be disposed of onto the garden, or wherever else compost is appropriate.
Normally the only plumbing is a ventilator pipe that allows smell to escape. Usually this is assisted by a fan.
Some require the addition of dry-matter like sawdust, though increasingly those for boats do not.
Better to view the page at EcoToilets than me explain. You probably will not yet see these very often, but they are becoming increasingly popular as they are eco-friendly and do not need a pump-out facility.