Very carefully.
A boat cruising in US waters pretty much has to have a holding tank rather than flush the toilets directly overboard. That’s because the US has laws preventing overboard discharge within 3 miles of the coast. Never mind that many coastal cities pump their sewage into the ocean as a matter of course (Miami), or regularly have accidents whenever it happens to rain too much (Tampa). Or that the real pollution problem in our oceans is caused by fertilizer runoff from residences, golf courses, and farmland. It stinks but that’s the way things are.
When being inspected by the Coast Guard usually the first thing they want to see is your Marine Sanitation Device, which is their official term for the commode, to make sure it is properly secured. In typical government fashion, the laws only apply to the toilets themselves. It is perfectly legal to go in a bucket and toss it overboard.
We can hold it comfortably for about ten days, which is pretty good for having 6 people aboard, but usually empty the tank on a weekly schedule. The tank can be pumped out at a shore-side facility such as a marina or fuel dock, or by a special boat that comes to us. Additionally, most boats also have their own pumps so they can dump overboard when beyond the 3-mile limit. We do all of the above.
When offshore, we empty the tank with a macerator pump, which has little blades like a kitchen sink disposal. The kids particularly enjoy watching our muddy wake while the pump does its business, but it isn’t all fun and games. The thing is notorious for breaking down and I have had to rebuild it multiple times. Every aspect of the process related to the tank is fraught with danger. Poo under pressure is never a good thing and I have witnessed a couple nasty accidents during dockside pumpouts, but have fortunately never experienced one myself.
Outside the US, the holding tanks are usually dispensed with and the goods go straight overboard. The Caribbean is full of boats doing this and it doesn’t seem to be a problem. From what I’ve heard, though, you aren’t allowed to flush paper in the Caribbean. Go figure.
The marine toilet is a bit different from those typically found in a house. Household toilets operate by gravity, which is not quite as reliable on something that moves the way a boat sometimes does. You want to deposit that stuff in a safe place where it can’t get back out except on your terms. Marine toilets operate on principles similar to those on an airplane, but rather than a simple device that empties the bowl in one big vacuum flush at the push of a button, like on a plane, our toilet has handles and levers and must be pumped manually. It’s definitely a more complicated procedure and most guests require a briefing. If you’ve been aboard, you’ve probably experienced it for yourself.
There are several different toilets types available for boats. Our current one was selected because it was the cheapest and most commonly available, but certainly not the best. It was installed as an expediency after I canned the four toilets that were on the boat when I bought her.
That was over two years ago and six of us have been enjoying it daily for almost a year. It has proven surprisingly reliable, but when it does have a problem, it immediately goes to the top of the project list. Usually the problem isn’t discovered until someone has to use it. In a pinch, we get the bucket out. Installing a second toilet is somewhere further down the project list and staying there for now.
The biggest challenge to our toilet’s regularity is the kids’ toilet paper use. Every once in a while, one of the kids will use about half a roll of TP and clog it up. They have all been amply warned, so when it happens the culprit becomes my special helper for the unclogging. You can’t just use a plunger the way you would in a house (remember, poo + pressure = bad). You have to open the hoses until you can find the clog and clear the line. It’s a messy, messy job. So far there haven’t been any repeat offenders.