Water is a necessary and valuable resource. When crossing open oceans in a slow moving sailboat you cannot use water the way we are used to, nor when you sail into the Pacific can you rely on getting potable water everywhere. With a watermaker onboard we can make do without relying on getting water on our destinations.


By Kaare   |   2022-10-21


If you go beyond the Caribbean you definitely need a watermaker to ensure an adequate amount of clean fresh drinkable water.


Selecting a watermaker

There are a large number of watermakers out there in the market. The technology behind the different models are basically the same, the variables are the degree of automation, the energy consumption per liter water produced, the amount of water produced pr hour, and finally how much liberty you have in placing the components when installing it in your boat. The quality of the components are off course also a issue, but this is very difficult for a layman to evaluate. We settled on a Aquatec DD500 12V version. Aquatec watermakers are manufactured and distributed by a German company based in Hamburg. The reasons we chose this particular brand are the following:

  • There is no automation in this model, which means there are less things which can break down.
  • Energy consumption is not the lowest, but again the watermakers with energy recovery are more technical advanced and therefore more likely to break.
  • The DD500 model produces 55 liters per hour, which means we need to run it for an hour or two every 4 to 5 days.
  • It is designed and built in Germany.

Traveling to Hamburg to pick it up, we were impressed when we came to the factory. The factory is a small one-man company, but they have been making watermakers for a very long time (father to son) and everything was in an impeccable order. Our purchase was laid out on the table, and the owner meticulously walked us through every detail, and even changed the setup on the spot based upon our needs.



When you plan where to install a watermaker you need to consider a number of things before settling on where to put it:


Water intake

You want to have the intake in a place which always is below the water so you do not suck air. The best place for that is usually behind the keel, but in many cases that will involve piping the saltwater a long way through the boat. You also need to have a decent size inlet, minimum size is 1/2 inch, but preferably a little larger. It is possible to use an existing intake, but you have to be sure it will be large enough to handle both the original function and the watermakers demand at the same time, and finally it needs to be located deep enough under the waterline to ensure the feeder pump also can be placed under the waterline.


We chose to use the existing intake for the forward toilet. It is located deep enough and almost at the centerline of the boat just in front of the keel, and it is submerged all the time. The input diameter is only 1/2 inch, but since we will not be using the toilet at the same time as the watermaker, it will do. Finally in order to ensure no backflow from the toilet we installed a one-way valve on the pipe to the toilet, and a cut-off valve on the pipe to the watermaker. That way we can ensure clean water for the watermaker, and be able to shut the watermaker off the system completely (cleaning and servicing).


Waste outlet

You have to get rid of the brine, and in some cases, the cleaning solutions from the watermaker. That pipe can be ducted at some length through the boat, but it is a good idea to minimize the pipe distance, both in terms of not having water standing in the pipe for long, and because it is difficult to trace a water pipe for long distances in the boat. When connecting the outlet to the waste-pipe be sure to connect it well above the waterline, and to have an upward bend on the outlet pipe just before connecting to the waste-pipe. That way you will not get backfill of the outlet pipe when the waste-pipe is in use.


We chose to use the waste-pipe from the shower pump in the forward head. It is easy to get to, and it is close to the intended position of the watermaker.


Freshwater access

In order to flush the watermaker after each use, we need to have access to the boats fresh water system. Again piping is an issue, but connecting to the water supply in the forward head is easy. A word of caution: be sure to install a shutoff-valve (ballofix or similar) where you connect to the existing water supply. That makes it easier to service filters, and the likes, without having to depressurize the entire system. We did not install this shut-off valve, and I regret that today.


Connection to the water tank

You have to consider where to connect to your water tank. Long piping is again an issue, because you do not want to have freshwater standing in that pipe for long. One of the best places to attach to is the filling pipe for that tank. Usually that is easy to get to, however it is also usually a very large diameter, which makes it a little more difficult to connect the very small diameter pipe from the watermaker (3/8th inch), however it is possible to find a number of suitable fittings. Be sure to connect the watermaker pipe with an upward loop to avoid backfilling when filling the water tank with city-water.


Power supply

The Aquatec 12V watermaker needs a power supply up to 60A. This means that you carefully have to consider the cable distance to and from the batteries. In our case placing the watermaker in the front of the boat meant that we needed at least 50mm2 cable. Luckily we also have both an anchor winch, and a bow thruster located at the front. To facilitate these two systems we have 125mm2 cable from the batteries to the bow. By connecting the watermaker to these cables we can ensure adequate cable dimension. This off cause means that we will have to remember not running watermaker, bow thruster and anchor winch at the same time,


Installing the watermaker parts in Iris

The Aquatec watermaker have the advantage of being modular, which means we can chose to put the different components where they can fit. We chose the following locations for the components:

  • the Reverse-Osmosis membrane is placed under the forward bunk in starboard side, all the way to the front.
  • The high pressure pump is located on top of the bow thruster also under the forward bunk, and right next to the battery for the bow thruster.
  • The feeder pump, strainer, and control valves for sea water intake, freshwater flush and cleaning cycle, are all located under the floorboards right next to the forward head. With this location it is possible to have an upward flow of water from the intake to the feeder pump, and still keep the feeder pump below the waterline.
  • The control panel along with the pressure gauge for the feed water is located in the closet on the port side in the forward head.
  • Filters and connection to the fresh water system are located underneath the sink also in the forward head.
  • The tank for the cleaning process is not mounted in a permanent place, since that would take up valuable storage space. Instead we devised a solution where the tank is dismantable by means of two garden hose connectors. That way we can prepare the cleaning solution in the galley and subsequently temporarily mount the tank and run the cleaning cycle. It is a little more complicated, but since cleaning is rarely done, the positive gain in storage space outweighs the more complicated usage.
  • The test outlet for the production water is located next to the sink in the forward head. That way production water can be discarded automatically in the startup of every production run.


Important tips and tricks

  • The RO-membrane will be damage if it comes into contact with chlorine. Most freshwater systems use some measure of chlorine in the tap-water. Therefore it is necessary to install an active carbon filter on the fresh water inlet to ensure the removal of chlorine.
  • The feeder pump can be damaged if the fresh water flush exceeds 2.0 bar. Since our fresh water system runs on 2.8 bar it is necessary to install a pressure reduction valve and -gauge. The valve should be placed in conjunction with the active carbon filter, but once it has been properly calibrated there is no need for further adjustments.
  • It can be difficult to get the system started if there is too much air in the system. In order to ease the deairing of the system we have mounted an automatic deairing valve right after the 5-micron filter.
  • The feeder pump must not be allowed to run dry. To ensure this we have the control gauge for the feeder pump. Whenever the feeder pump is working correctly this will display a positive pressure. It is a good idea to mount this gauge close to the control panel so you are able to monitor the feeder pump pressure when manipulating the control panel.

The small production water pipes (3/8 inch) are connected by a simple push-connection. You push the pipe 20mm into the connector, and this will seal the pipe. In order to ensure you push into the full 20mm into the connector it is a good idea to mark the 20mm BEFORE you push the pipe into the connector. Failure to push it completely in will result in a leaking connection.