How do I winterize my boat and its onboard systems?
I'm laying up my 32-foot sailing yacht for winter, with a diesel inboard, freshwater tank, calorifier and sea toilet. What should I drain, where should I use antifreeze, and what needs checking if I leave her afloat?
Answer
Winterise your boat by draining or frost-protecting every water circuit, servicing the engine, maintaining the batteries and cleaning the accommodation, then keeping it dry and ventilated. First decide whether she will winter ashore or afloat, as this determines how you handle seacocks, bilge pumps, batteries and winter inspections.
Check every water circuit
Before draining anything, list everything that holds water: engine cooling, freshwater plumbing, calorifier, toilet, holding tank, shower sump, deck wash and any air-conditioning circuit or watermaker. Overlooked pumps, strainers and low hose loops are common sites of frost damage.
Check the engine and equipment manuals for specific lay-up instructions. Photograph valve positions and label disconnected hoses to make spring recommissioning easier.
- Ashore: have the yard position and support the boat correctly. Do not move props or work beneath a suspended hull.
- Afloat: check mooring lines, chafe protection, fenders, cockpit drains and bilge-pump operation before leaving.
- Inspect seacocks, hose tails and clips, and record anything that needs replacing.
Afloat, close seacocks for systems taken out of service, but keep essential drainage and operating systems working. Ashore, drain valve bodies and leave valves in the position specified by their manufacturer.
Protect domestic water systems
Drain the freshwater tank, then open every hot and cold outlet, including the transom shower. Drain the pump strainer, accumulator where fitted and low points. Running the pump briefly may clear residual water, but prolonged dry running can damage some pumps.
Switch off the calorifier's electrical supply and let the water cool. Open a hot tap, then drain the calorifier through its proper drain valve. Bypass it before introducing antifreeze, or you may waste enough product to fill the entire cylinder.
- Drain everything accessible, including shower sumps and deck-wash plumbing.
- Where complete drainage is impossible, use propylene-glycol winterising antifreeze specifically labelled for potable-water systems.
- Feed it through the pump and open each outlet separately until adequately protected fluid reaches it. Follow the product's dilution instructions.
- Empty the holding tank at a pump-out station, rinse it and winterise the toilet's intake, pump and discharge circuit according to its manual.
Antifreeze in the toilet bowl alone does not protect the pump or inlet hose. Avoid vodka, household alcohol and automotive antifreeze in drinking-water plumbing. Check antifreeze compatibility with toilet seals and other equipment. Watermakers need their own flushing or pickling procedure.
Service engines and cooling circuits
Run the engine to operating temperature before changing the oil and oil filter, following its service schedule. Inspect belts, hoses, engine mounts and the raw-water impeller. Drain water from the fuel separator and replace filters when due.