Why You Need to Winterize
Not winterizing your boat’s freshwater system can cause the same kind of costly freeze damage as failing to winterize your engine. If water remains trapped in tanks, pumps, faucets, hoses, fittings, water heaters or accumulator tanks, freezing temperatures can split lines, crack components and create leaks that may not appear until spring commissioning.
Winterizing your boat’s potable water system is a straightforward process: drain as much water as possible, bypass or drain the water heater, then run non-toxic marine antifreeze through every fixture until the system is protected.
- Before You Begin
- Step One: Open the Faucets
- Step Two: Add Antifreeze
- Step Three: Run Antifreeze Through the System
- About Antifreeze
- Best Practice for Antifreeze Disposal
- Freshwater System Winterizing FAQ
Before You Begin
If your boat has a water heater, we suggest installing a water heater bypass winterization kit. A bypass kit isolates the water heater so you can drain it separately instead of filling the entire tank with antifreeze. This saves time, reduces antifreeze use and makes spring flushing easier.
If the water heater is electric and relies on an internal heating element, disconnect it from the electrical system before draining it. This prevents the heating element from burning out if the heater is accidentally turned on while empty. Mark the electrical connection with a reminder to refill the heater before restoring power in spring.
A water heater bypass winterization kit saves time and money by eliminating the need to fill the water heater with antifreeze.
If your water system has an accumulator tank, drain it as well. Remove the hoses if needed. If the tank does not drain completely, blow through the T connection to force out trapped water or remove the tank and shake out any remaining water. Reinstall it and reconnect the hoses before running antifreeze through the system.
Before starting, gather enough non-toxic propylene glycol marine antifreeze, basic hand tools, rags, a bucket and any winterization fittings your system requires. Check the owner’s manuals for your pump, water heater and onboard plumbing equipment if you are unsure about drain points or bypass procedures.
Step One: Open the Faucets
Open all faucets and turn on the freshwater pump. Allow the faucets to run until the freshwater tank is empty and the flow stops. Then close all faucets and turn the pump off.
Do not forget secondary fixtures such as cockpit showers, transom showers, wet bars, washdown-style freshwater outlets, ice maker supply lines or freshwater heads if connected to the potable system. Any fixture or branch line that contains water must be drained and protected.
Step Two: Add Antifreeze
Pour four to six gallons of West Marine Pure Oceans non-toxic antifreeze into your boat’s potable water storage tank. Larger systems, multiple heads, long plumbing runs or boats without a water heater bypass may require more.
Use only non-toxic propylene glycol antifreeze designed for potable water and marine winterization. Do not use automotive antifreeze in your freshwater system.
Step Three: Run Antifreeze Through the System
Turn the pump on and open the hot water fixture farthest from the pump. This will draw antifreeze through the hot water side of the system. When you see antifreeze coming out of the fixture, turn it off. Next, open the corresponding cold water fixture until antifreeze appears, then turn it off.
Repeat this process for every fixture on the boat, working your way back toward the fixture closest to the pump. Include showers, cockpit sprayers, transom showers and any other freshwater outlets. When finished, turn the pump off.
By following these steps, you help ensure that your boat’s freshwater delivery system will be protected through freezing conditions and ready to recommission in spring.
West Marine Propylene Glycol Antifreeze
About Antifreeze
There are two common types of antifreeze. Automotive antifreeze, such as ethylene glycol, is highly toxic and should never be used to winterize potable water systems on boats. Instead, use non-toxic propylene glycol antifreeze made for marine engine and water system winterization.
For northern regions where temperatures can drop below zero, we recommend antifreeze with a freeze rating of at least -100°F. The antifreeze that enters the system at its rated strength can become diluted by residual water left in tanks, hoses and fixtures. That dilution raises the actual freeze protection level, which is why stronger antifreeze can provide more margin of safety.
The small cost difference between -50°F, -60°F and -100°F antifreeze is often worth it for the added protection, especially in colder climates or systems that are difficult to drain completely.
Best Practice for Antifreeze Disposal
Even though West Marine propylene glycol antifreeze is non-toxic, best practice dictates that you not discharge it onto land, into storm drains or directly into the water. After use, dispose of used antifreeze in a manner consistent with federal, state and local regulations.
When recommissioning in spring, flush the system thoroughly with fresh water until the antifreeze color and odor are gone. Collect and dispose of flushed antifreeze responsibly where required.
Freshwater System Winterizing FAQ
Can I use automotive antifreeze in my boat’s freshwater system?
No. Automotive antifreeze is toxic and should not be used in potable water systems. Use non-toxic propylene glycol antifreeze designed for marine water system winterization.
Do I need to bypass my water heater?
A water heater bypass is strongly recommended. It allows you to drain the heater separately and avoid filling the entire tank with antifreeze.
How much antifreeze do I need to winterize a boat freshwater system?
Many systems require four to six gallons, but larger boats, long plumbing runs and systems without a water heater bypass may require more.
Do I need to winterize every faucet and shower?
Yes. Every hot and cold fixture, shower, sprayer and freshwater outlet should run until antifreeze appears.
What should I do in spring after using antifreeze?
Flush the system thoroughly with fresh water until antifreeze color and odor are gone. Refill the water heater before restoring electrical power to it.