Why have a watermaker? We use a lot of fresh water on board. Laundry, dishes, showers, head flushing, drinking, and cooking. Without conserving, we each use about 20 gallons of water per day. With a 250 gallon water tank, we have about six days before we need to refill it. Usually, that means paying for a night at a marina or going home. With a watermaker, we can choose to stay out longer and visit marinas for other reasons than for refilling the water tank. Sometimes there is water available without paying for a night at the marina, though not often. During the summer in times of droughts, water is scarce and may not be available at all, especially in British Columbia. Also in the islands of BC, the cedar tree tannins turn much of the fresh water supply brown. It is potable water, but not very appealing to drink or even to shower with. Finally, the further north we venture, marina services are sparse. We decided that installing a watermaker is a good idea.
Marine watermakers use a process of reverse osmosis. The salt water is forced through a membrane that separates the fresh water from the brine. The fresh water is diverted to the fresh water tank and the salt brine goes overboard. There is a sensor that determines when the total dissolved solids (salt) are reduced to an acceptable level before it diverts it to the tank.
Watermakers are sized and rated in gallons produced per 24 hours. They are not generally expected to be operated continually, rather they are sized to match to your estimated useage and how long you expect to run the generator. They typically run on AC, not DC. We usually run the generator up to 4 hours per day for heat and to charge the batteries. Our watermaker is rated at 500 gallons per day (24 hours), or about 21 gallons per hour. So we could fill our water tank by running the watermaker for 12 hours. More realistically, we will run it when the generator is in use to keep our tanks at a reasonable level, replenishing as we use it every couple of days.
Installation is time consuming so you can save a lot of money doing it yourself. Manufacturers offer their watermakers as individual components or with most of those components contained in a space saving frame. With individual components, you can mount them wherever you can find room. We got a framed version and mounted it on a shelf in the engine room with easy access to the controls and to filters that will need to be periodically replaced.
The salt water supply is provided by an existing through hull that was being used for the salt water anchor wash down. Fresh water is much better for rinsing the anchor and chain, so I connected the anchor wash down pump to the fresh water supply and used the through hull to supply the watermaker. No new holes in the boat needed. The salt water passes through a coarse filter before being pumped to the main filter on the watermaker.
Three other plumbing connections are required, one for carrying the fresh water to the tank, another for carrying the brine overboard, and the final connection to the fresh water pump to provide a fresh water flush of the watermaker’s filters. I teed the 3/8″ fresh water product line into the water tank’s air vent on the top of the tank.
The 1/2″ brine discharge line is teed into the drain hose for the back deck.
Finally, I teed the 1/2″ fresh water flush line into the main water line that supplies the faucets on the boat. After every useage, the system is completely flushed clean with fresh water. It takes a minimum of 5 minutes and keeps the filters and membranes clean and long lasting. If the watermaker is not being used frequently, like over the winter, the system can be programmed to automatically run the fresh water flush every week to keep bacteria from growing.
With the plumbing complete, I connected the watermaker to the boat’s AC power supply and installed the remote panel at the helm. The remote panel allows operation and monitoring at the helm rather than going into the engine room. There is a low pressure pump and a high pressure pump that together pull 23 amps. The distance to the AC distribution panel was about 35 feet, so using an electrical chart online I determined the appropriate size of wire. In this case, 10 gauge would have worked OK, but to be extra safe I used 8 gauge wire. The wire needs to be able to handle the amps and the distance without overheating and causing a fire. The watermaker will be able to run with either the generator or when the boat is plugged into shore power at a marina.
We now can enjoy an endless supply of fresh water while out boating!