Life aboard
How to Use a Marine Toilet on a Boat — The Heads Explained
Published · Last checked October 2026
To use a manual marine toilet (the heads), check the seacocks are open, set the lever to 'wet' and pump to add water to the bowl. After use, switch to 'dry' or 'flush' and pump steadily until the bowl is empty and the pipe is clear, typically 10 to 20 strokes or more. Put nothing in except human waste and a small amount of toilet paper. Close the seacocks when you leave the boat or in rough weather.
How a marine toilet works
A yacht toilet draws in seawater through one seacock and pumps waste out through another, either overboard or into a holding tank. A hand pump with a lever or valve controls whether water comes in to flush the bowl, or whether the pump only empties it. Because the outlet runs through the hull, a toilet left open can siphon seawater into the boat, which is why seacocks matter.
Step by step
- Check the inlet and outlet seacocks (and the holding tank valve, if fitted) are open.
- Set the lever to 'wet' or 'flush' and pump a little water into the bowl.
- Use the toilet. Use only a small amount of thin toilet paper.
- Pump with the lever on 'flush' until the bowl is clean.
- Switch to 'dry' and keep pumping until the bowl is empty and the outlet pipe is clear, so waste does not sit in the hose.
- Leave the lever on 'dry' and the lid down.
Holding tanks and the law
| Situation | Usual practice |
|---|---|
| In a marina or harbour | Use shore toilets or a holding tank; do not discharge overboard |
| Inland waterways and some harbours | Discharge is prohibited; holding tanks are required |
| At sea, well offshore | Overboard discharge is generally permitted for small craft, subject to local rules |
| Pump-out station | Empty the holding tank here |
Rules vary by country and harbour. Some Mediterranean and Baltic areas have strict no-discharge rules and fines. Check local regulations and the environmental awareness lesson.
Safety and troubleshooting
- Close the seacocks when leaving the boat and in heavy weather, to stop back-siphoning.
- Hard to pump? Something is probably blocked. Do not force it; tell the skipper.
- Smells usually come from the hose or a full holding tank; flush with plenty of fresh seawater.
- Brace yourself when the boat is heeled or rolling. Many skippers ask everyone to sit down to use the heads at sea.
Learn more about the boat's systems in the vessel safety equipment lesson.