Separating water and boats is no easy task. But when it comes to winterizing, a major part of the effort is to do just that.

Most boats have some kind of fresh water system, whether it is a single tank and a manual faucet or a vast system with several tanks, electric pumps, multiple outlets and a water heater. But the principles are the same in each case: You need to get the water out and the antifreeze in.

Fail to do so and the residual water in your tanks and lines can freeze when the mercury drops, leaving them vulnerable to damage and leaks. For the same reason, bilges should be dried, the waste tank emptied and systems that use sea water should be drained and the thru-hulls closed.

Whether stored in the water or on land, temperatures inside any boat can drop precipitiously. Systems that use water must be purged to avoid damage to lines during a freeze.The best way to ensure that all these steps get done is to develop a check list. Check lists have worked well for pilots and shuttle commanders for years–and there is no reason they won't work for you. The list should note the systems that require attention, the amount of supplies (such as antifreeze) needed and as any special tools required to complete the task.

GET THE WATER OUT

The first step in winterizing your water system is to get all the water you can out of the system. That means letting the pump run, with all the faucets open until nothing but air comes out. Because you are purging water lines, as well as the tanks, be sure to include all sinks, showers, washdowns and anything else that draws fresh water.

A special case is the water heater. The best strategy is to fit your boat with a bypass kit that will allow you to drain the water heater dry, and then skip the antifreeze. The reason is simple: if you forget to drain the antifreeze out of it in the spring and start up your heater, the smell and taste of cooked antifreeze will be with you for a long, long time.

The antifreeze of choice for this application is non-toxic propylene glycol, which is sold for marine or RV potable water systems. The antifreeze is USP or "food grade," because it is used with drinking water. It is usually pink and has a rated slush point of -50 degrees. Under no circumstances should automotive or ethylene glycol antifreeze be used in a water system, because these products are toxic.

Pour your bottles of antifreeze into the empty water tanks through the same deck fill you use to add water. Don't be tempted to dilute the antifreeze before adding it to your tank. It will mix with the residual water left in the system, and any further dilution will reduce the protection it provides.

You will not fill your tank (that would be expensive and unnecessary). Rather, the goal is to add enough to spread the antifreeze throughout your entire water system. The exact amount will be different on each vessel. When in doubt, buy more. You can always use it elsewhere on the boat, or hold it for the following season.

When the tanks contain enough antifreeze, start up the water pump with all of the faucets and outlets closed except the one furthest from the pump. Leave it on until pure antifreeze comes out of the outlet. Allow it to run long enough to flush all the fresh water out of the drain lines (all drains must be flushed with antifreeze or residual fresh water in the line can freeze.)