Other than being aware of the need for fresh water, the periodic challenges procuring same. I had given little thought to the matter. As the refit progressed, brain began to turn to water, and based on an enthusiastic recommendation from a cruiser met in Curacao, I first began to explore the company Seawater Pro. I thren asked around online and gained an understanding of other systems (and their cost) and eventually returned to Seawater Pro. Why? While most other systems are more refined and efficient, and are commensurately more expensive, with more esoteric pumps and motors. This makes sense given the traditional high cost of battery capacity and electricity generation, however in a real world use case, electrical efficiency is no longer a key consideration.
So, Seawater Pro offers a range of systems, but their system typically comrprises:
- Reverse osmosis membranes.
- seawater pumps - a small 12VDC liftpump and a much larger high pressure pump, 12v, or 120/240VAC)
- Electrical circuits for powering same, incl switching and protection..
- A pressure regulator to ensure the membranes see adequate but not excessive pressure.
- An intake strainer* and two stages of pre filtration.
- A means to discharge brine. (the salts and impourities removed from the water)
- A means to flush the system with fresh water, to ensure that marine organisms don't colonize and contaminate the system. The seawater pro system has a flush timer and circuit to accomplish this. (this is a battery powered sprinkler timer.)
- Gauges to measure the input and output pressure of the sytem, and a TDS (Total Dissolved Solids) meter to infer water quality.
Connections
Power - two connections. the system requires two power sources - 12v at nominal current to operate the boost pump, and sufficient AC or DC power to operate the Main Pump, depending on pump motor chosen.
Plumbing- four connections. The system requires a seawater intake via a strainer, and a brine discharge overboard. Purified water should be discharged to the tank via a diverter valve to also faciliate filling of jerry cans and an initial system flush. System backflush requres a pressure water connection to the timer.
Power Options
The 220v 50-hz AC motor requires 1000w to run but much more to start. This inrush current must be considered in sizing the power supply.. My 1600VA iVictron Multiplus nverter/charger can provide a peak of 2800w, and 1100Wcontinuous at 40 deg c, but when power factor and inrush current are considered it is undersized.
- The industry standard 1hp AC farm duty motor is brushless and very long lived. (and can probably be serviced anwhere in the world, or easily replaced)
- The AC motor supports 40gph (151 litres) dual membrane operation vs 17GPH for the DC motor.
- The DC motor requires brushes and is known to be less reilable.
This belatedly brings about the real challengie with this (or any) system, and that is location. Because of the size, power and plumbing requirements, there is no signle, obvious location. The only area in the boat which provides proximity to all of the required connection points in the forepeak, which is not a bad choice anyway. This may change when it comes time to install.
https://seawaterpro.com/
https://skwatermakers.net/collections/watermakers/products/ez-501
https://citimarinestore.com/en/village-marine-ltm-series-watermaker/16933-parker-ltm-145-watermaker-145-gpd-12v-membrane-included.html
