27/10/2026
Winterising your marine toilet: a quick guide ❄️
Freezing temperatures can cause damage to marine plumbing and toilet mechanisms, so a little preparation before winter can save a lot of hassle later on.
1. Know where your flush water comes from. Is your toilet supplied by the boat’s freshwater system, or does it draw water from outside the boat? The winterisation process is different for each.
2. Treat the system before winter. For toilets flushed with outside water, LeeSan recommends drawing an anti-scale solution through the system, leaving it for 24 hours, then flushing it out with a strong mix of water and soft washing-up liquid before draining the system.
For freshwater-fed systems, an anti-scale treatment can be flushed through first, followed by antifreeze specifically designed for domestic freshwater systems.
3. Drain the toilet if you’re not using antifreeze. The correct method depends on the type of toilet you have. Macerator, dump-through, hand-pump and Vacuflush toilets all have different draining procedures, so make sure you follow the correct method for your system.
4. Use winter as a chance to inspect the system. Switch off the water pump, check hose connections for leaks, tighten hose clips and look for worn hoses, seals or components that may need replacing.
⚠️ Important: Never use normal vehicle antifreeze in a domestic plumbing system. Only use antifreeze intended for freshwater domestic systems, and flush it thoroughly with fresh water when recommissioning.
A little winter preparation now can help prevent a much bigger job in spring.
Read the full LeeSan winterisation guide at leesan.com/winterisation.
