Why it cracks
Water expands when it freezes and splits hoses, pump housings and tanks. A little water in a low point is enough. So just running a pump dry is not enough. Water remains in the pump housing and in the low sections of the hoses.
What you need
| Item | Used for |
|---|---|
| Propylene glycol for boats or caravans, premixed | Toilet, pumps, drains |
| Screwdriver or socket wrench | Loosening hoses and quick connectors |
| Short hose and funnel | Letting the pump draw glycol from the container |
| Bucket and rags | Water that runs out |
| Container for collection | Old glycol to the recycling station |
Allow 4 to 8 litres for a toilet or pump. Long hoses need more.
Choose the right glycol
- Use propylene glycol (often pink). The Swedish Boating Union advises against ethylene glycol because it is highly toxic to people and the environment.
- Jabsco says the same: never car antifreeze in the toilet or raw water system.
- Avoid cheap antifreeze containing alcohol. Alcohol makes rubber swell, for example diaphragms, impellers and check valves. If the container says flammable, choose another one.
- Premixed antifreeze should not be diluted. Water raises the freezing point.
The fresh water system
- Empty the fresh water tank.
- Open all taps, cold and hot, including the shower.
- Drain the water heater according to its manual.
- Drain the water pump. Disconnect the hoses at the pump and run it briefly so the water comes out.
- Leave the taps open over the winter.
Read the manual for your pump and water heater. Some systems should be drained completely, others filled with antifreeze.
The toilet (seawater flush)
- Pump out the holding tank before the boat is hauled out and flush the system with clean water.
- Close the seacock and switch off power to the pumps.
- Disconnect the inlet at the toilet pump and put a short hose into the antifreeze container.
- Pump or flush until antifreeze has gone all the way to the holding tank or outlet. The first pink liquid is mixed with water, so keep going a little longer.
- Don't forget the hose between the seacock and the pump. Disconnect it at the pump, pour in antifreeze and reconnect it. This is the part most often forgotten.
- If you have a macerator, run it for about 30 seconds so the antifreeze passes through it. Don't run it dry for long.
- Leave the seacocks closed over the winter.
Common mistakes
- Glycol only on the outlet side. The inlet hose fills with water and splits.
- Bleach or strong cleaners in the toilet. They break down seals. Use a mild product approved by the toilet maker.
- Cooking oil or mineral oil to lubricate seals. Follow the maker's advice, which specifies silicone-based lubricant on some parts.
- Running a pump in spring against a closed seacock. Open the seacock first.
Environment
Don't let antifreeze run onto the ground or into the water. Collect it and hand it in as hazardous waste at the club's waste station or the local recycling centre.
Frequently asked questions
Can I use car coolant?
No. Car coolant is usually ethylene glycol, which is toxic. Use propylene glycol intended for boats or caravans.
How much glycol is needed?
Jabsco estimates 4 to 8 litres for a toilet or pump. Long hoses need more. Keep going until the fluid is pink at every outlet.
Can I flush the fresh water system with glycol instead of draining it?
You can use propylene glycol, but follow the manual for the pump and water heater. Many owners just drain the system and leave the taps open.
Should the seacocks be open or closed?
Closed over the winter. Open them in spring before switching on the pumps.