Echotec artwork - clear background

AC Inverter Watermakers - Frequently Asked Questions (FAQs)

The water consumption on a cruising yacht depends on the number of crew, the use of the vessel and the way the water is consumed. It ranges from 13 gallons per day for a cruising couple who uses water conservatively to 300 gallons and more on larger charter boats.

If you know your daily water demand, simply divide the amount needed by the hours your generator runs every day. The result is the GPH rating of the watermaker that suits best your application. E.g.: 50 gallons / 190 liters per day consumption at 1.5 hours generator running time requires a watermaker with a minimum capacity of 33 gallons / 125 liters per hour.

It should be avoided that the generator runs solely for producing fresh water. Keep in mind that on larger yachts where the generator runs continuously or most of the day, a larger capacity watermaker will require shorter running times; resulting in less maintenance and lower filtration cost.

If the main engine is used for charging and/or powering the fridge/freezer regularly, the installation of a high-output belt driven system should also be considered.

The highly power efficient ECHOTec small generator/inverter series can be started by small to medium sized generators or in The highly power efficient ECHOTec small generator/inverter series can be started by small to medium sized generators or inverters and leaves ample power for other equipment when running. E.g.: The system 780-AML-2, with a production of 31 GPH draws only 8.4 Amps at 115 VAC or 4.2 Amps at 230 VAC. Even a 2 KW generator or inverter will easily handle the startup load of the desalination system and optional boost pump.

High output AC yacht desalination systems consume 8.2 to 9.5 Amps (A) at 230 VAC or 16.4 Amps at 115 VAC for a production of 70 gallons or 260 liters per hour. This will require a generator of 5 KW to start the system and leaves about 3 KW for other equipment when running.

No. Having a generator on board allows you to use a high capacity desalination system at a far more favorable price/output ratio.

If you like the advantage of a back-up in case of a generator failure, take a look at the ECHOTec small generator/inverter series. These systems produce large amounts of fresh water, are highly energy efficient and can be powered via an inverter at the same total power consumption as high output DC systems.

Reducing the amount of energy required to produce a given amount of fresh water by desalination is a challenge that has resulted in extensive research and development by various RO (reverse osmosis) equipment manufacturers and led to the production and marketing of what are commonly referred to as “Energy Recovery” desalination systems.

Energy Recovery systems used on yachts ‘recover’ some of the energy that is still available in the pressurized brine reject water in conventional systems. For smaller DC electrical yacht watermakers, this is achieved by the use of a complex single piston and valve ‘intensifier’ system in which the pressurized reject water is used to assist in driving the single cylinder high pressure pump.

The actual power savings achieved when compared to advanced conventional triplex plunger pump systems e.g.: ECHOTec, ranges in reality from 0% on older survivor type energy recovery watermakers (PUR or Katadyn) to 45% on later models. At a production of 32 gallons / 120 liters per day, the typical water demand on a larger live aboard cruising yacht, the archived power saving would be less than 2 amps at 230 V AC per day and is therefore negligible. Recovering such small amount of energy makes no sense from a cost saving perspective.

Energy Recovery type watermakers have other significant disadvantages:

1) Conventional ‘triplex’ HP pump systems ensure stable operating pressure, extending the life of your system's reverse-osmosis (RO) membranes. Dow Filmtec, major manufacturer of RO membranes, warn in their product manuals to avoid damage due to ‘hydraulic shock’ caused by significant pressure variations. The single piston ‘intensifier’ style energy recovery watermakers, by their nature, produce a continuous repetitive pressure pulse (hydraulic shock) throughout their operation. A stable operating pressure extends the life of the membrane(s) by eliminating the detrimental pressure pulses.

2) Unlike ‘triplex’ plunger pumps, energy recovery devices are not field serviceable due to their highly complex nature. Any significant defect requires the unit to be returned to the manufacturer or their factory trained service centre.

3) Depending on the vessel, a modern conventional style watermaker installation may require a feed pump. ECHOTec uses highly reliable low pressure (8 – 20 psi [pounds per square inch]) magnetic drive boost pumps for best pre-filter cost efficiency and easy priming after filter changes, whereas energy recovery watermakers for yachts require large 100 psi pressure pumps in addition to the high pressure pump (pressure intensifier) which further complicates the system, increases the risk of breakdown, and necessitates the holding of expensive spare parts.

4) Due to the complex nature of the recovery device and often unnecessarily incorporated electronic circuits, prices for recovery type watermakers range from 60 to 95% higher than advanced conventional systems for the same fresh water output.

In conclusion, it is questionable if the relatively low power saving achieved by the application of energy recovery type desalinators aboard yachts can compensate for the considerable extra cost, complexity and consequently reduced reliability.

If you like the advantage of a DC back-up in case of a generator failure, take a look at the ECHOTec small generator/inverter series. These systems produce large amounts of fresh water, are highly energy efficient and can be powered via an inverter at the same total power consumption as high output DC systems.

If the desalination systems’ high pressure pump cannot be fitted well below the water level, a booster pump will be required. Although the high-pressure pump assists initial water draw, a booster pump improves the performance of the complete system.

A booster pump saves time and money as it helps to gain maximum pre-filter element life and to prime the system after pre-filter changes. It also avoids cavitation at the high-pressure pump intake that could lead to pitting of the pump head.

The power consumption is negligible as the booster pump adds pressure to the total required working pressure of the system. The booster pump is not needed for the fresh water flush procedure. The required pressure is created by the boats’ fresh water supply pump.

The fresh water flush exchanges the seawater in the membrane element/s with non-chlorinated fresh water. The simple flushing procedure avoids biological growth due to dying micro organisms contained in the seawater and dissolves mineral build up that may clog the membrane element/s. Repeated every 10 days the fresh water flush also avoids the need for chemical preservation, otherwise to be performed for long-term storage.

The fresh water flush is a useful feature. It exchanges the sea water in your membrane element/s with fresh water and therefore avoids biological growth that will clog the membrane, leading to reduced output and premature failure of the membrane element/s. Repeated every 10 days, it avoids the need for chemical preservation, usually performed for long-term storage.

The main advantage of the automatic fresh water flush is that it will repeat the flush during your absence, often at a user selectable interval.

However, usually boat owners disconnect the AC power primarily to exclude the chance of an electrical fire, the most common cause for lost boats together with galley fires! Now, when you need it the most, the automatic fresh water flush will not work as it relies on AC power. In addition, you would always need to leave your entire fresh water plumbing under pressure – not a good idea when your boat is unattended.

For your peace of mind, perform the easy chemical preservation procedure if you leave your boat for more than 10 days. The widely available preservative Sodium metabisulfite “pickles” your system for up to 12 months. All ECHOTec systems are supplied with enough preservative for three long term storages.

Provided the membrane element is in good condition, it “filters” to about 0.0005 micron. Virus (0.01 to 0.04 micron) or bacteria (0.1 to 15 micron) will not pass and in reality, waterborne diseases on board vessels using only desalinated water are un-heard of.

However, the condition of the vessels storage tank(s) and/or plumbing can be a concern and should be sterilized e.g.:

with chlorine on commissioning of the desalination system and as an occasional routine maintenance. The desalination system should not be operated in chemically contaminated waters, as the RO process will not safely remove all chemicals.

Active carbon filters after the tank and before the faucet are useful to remove chlorine from shore water but do not improve the watermaker product quality.

Another important consideration is the TDS level (the combined content of all inorganic and organic substances) in the product water. Depending on agency and location, the upper limit for safe drinking water is set to 500 - 1000 ppmTDS.

Drinking Water Regulations


The backwash is often mistaken for fresh water flush. Backwash refers to the return of the feed water stream in media filters often used on land based desalination systems where silt and other sediments would quickly clog the pre-filters.

It washes the collected contaminants back into the sea by lifting and tumbling the filter media under flow.

Yes. Manually operated DC system like the ECHOTec AML Series allow you to regulate the operating pressure in order to process feed water from fresh water in rivers and lakes to seawater in the Red Sea.

The fresh water output of most desalination systems is rated at a seawater feed temperature of 26˚Celsius or 78˚ Fahrenheit. Membrane productivity, however, is sensitive to changes in feedwater temperature. As water temperature changes, water flux changes almost linearly, due primarily to the diffusion rate of water through the RO membrane.

As a rule of thumb, membrane capacity changes about 2% per degree Celsius water temperature. At very low feed temperatures, pre-heating of the feedwater may be considered. A commonly used method of pre-heating is mixing part of the engines/generators seawater cooling return with the cold seawater, ideally to a temperature of 30˚ Celsius or 86˚ Fahrenheit.

Product water from any RO watermaker is extremely pure, has little salt content, is very soft and acidic due to the removal of alkaline mineral constituents of the seawater. Therefore, similar to rainwater, using RO product requires significantly more fresh water to rinse off soap, shampoo and other detergents.

ECHOTec is the first watermaker manufacturer to combat this problem by improving the RO product quality with a standard supplied post treatment system. The newly developed mineral dispenser returns some hardness to the water and offers a practical, low maintenance solution that saves up to 50% fresh water.

The ECHOTec post treatment element also contains a mixture of minerals that returns bicarbonate alkalinity, correcting pH only enough to reach a neutral equilibrium. This dramatically reduces corrosion on metal tanks, boilers, washing machines and plumbing due to acidic product water.

As the water is slightly re-mineralized, this will also improve the taste of the product water.

Yes. The pre-filter elements can be cleaned several times before you have to replace them.

You should use only pleated polyester pre-filter elements at the micron rating specified in the owner’s manual. String wound or fiber type filter elements cannot be cleaned, have a ten times lower filtration capacity and therefore are not cost efficient. Many household under-the-sink filter elements are made from the wrong material; they may fall apart in seawater which will cause fouling and damage to the membrane elements.

Other than most competitor brands, ECHOTec watermakers do not require proprietary consumables. All pre-filter housings and RO pressure vessels are built to standard sizes in order to allow replacement with widely available spare elements.

Remarks like: “consumables are manufactured exclusively to more demanding requirements and higher specifications” may indicate that this manufacturer’s product requires the purchase of proprietary spares and consumables at drastically elevated prices, only to meet the listed system specifications.

However, there is a vast difference between off-the-shelf consumables, especially within pre-filter cartridges: A laboratory test with a highly concentrated mixture of water and coarse test dust was performed to demonstrate relative performance between different types of pre-filter cartridges.

The test results below dramatically show that “inexpensive” string wound cartridges hold, depending on their filtration surface 80% less sediments. They can filter only 10% of the seawater than the twice as “expensive” pleated polyester cartridges.

Pleated polyester
Resin Bonded
Depth cartridges
Spun Polypropylene
String Wound
Solids removed:
12.0 oz. (340 grams)
7.0 oz. (199 grams)
3.3 oz. (94 grams)
2.5 oz. (71 grams)
2.1 oz. (60 grams)
Quantity filtered:
50.4 gals. (189 liters)
33.2 gals. (124 liters)
8.4 gals. (32 liters)
5.9 gals. (22 liters)
4.0 gals. (15 liters)

Other than spun or woven filters, pleated polyester cartridges can be cleaned several times before they need to be exchanged and therefore are more than 20 times as cost efficient!

For your comparison, ECHOTec pleated polyester cartridges have an effective filtration surface of 6 sq. ft. per 9-3/4" length; 2-3/4" O.D.; 1-1/16" I.D. element.

AC and belt driven watermakers work well with almost any quality RO membrane element. DC systems perform better with high rejection membranes.

In case you cannot obtain suitable quality consumables locally, all products are available economically priced and for same day shipping from

With proper maintenance, the life expectancy is 20 years and can last the yachts life time.

An important consideration in the choice of the right desalination system is the amount of airborne noise transmitted by the high pressure pump.

Rotary piston pumps run at very high speeds and create a loud pitching noise. Even so more advanced systems have full sound enclosures, they are not suitable for installations close to inhibited cabins.

Plunger or piston pumps are considerable less noisy and create lower frequencies as they run at low RPM. The ECHOTec triplex plunger pumps are the quietest high pressure pumps in the world. They are about 10 dB quieter than other brands on the market.

While many manufacturers are satisfied by simply assembling standard off-the-shelf parts, ECHOTec engineers and builds more proprietary components than most watermaker companies in order to achieve ultimate reliability, performance and cost efficient operation. What makes ECHOTec the practical choice for cruisers as well as commercial users is that all innovative system components are built to allow the use of widely available off-the-shelf consumables and spares.

The following is a list of system components especially designed or carefully selected to eliminate common problems associated with the operation and maintenance of on-board desalination systems.

1) Stainless steel spring-loaded automatic pressure regulator with single O-ring seal for superior reliability, constant working pressure and simple maintenance, versus needle valves with packing.

2) 24 V low voltage automatic breakers on the control panel actuate waterproof enclosed heavy-duty double pole relays for each pump in the system.

3) ECHOTec pleated polyester filter cartridges have an effective filtration surface of 6 sq. ft. per 2½” x 9¾" element. They can filter 3 times more seawater than cartridges commonly supplied by other manufacturers and 10 times more water than string wound filter cartridges, offered with do-it-yourself type watermakers.

4) ECHOTec is the first yacht watermaker, equipped with a unique pH buffer element. This cartridge contains a mixture of minerals that correct pH only enough to reach a neutral equilibrium in order to protect metal fresh water tanks, heaters and fittings. As the water is slightly re-mineralized, this will improve the taste and also makes soap rinse off easily, resulting in up to 50% lower fresh water consumption.

5) ECHOTec boost pumps are magnetic driven, have ceramic shafts, require no seals and have no metal parts in contact with seawater vs. commonly used bronze, brass or stainless pumps with easily corroding stainless shafts that often cause the mechanical shaft seals to fail.

6) Modular concept for space saving installation or super compact and self contained for fast and simple installations.

7) Field attachable high pressure fittings for clean do-it-yourself installations vs. standard supplied hose lengths with crimped fittings.

8) Custom build leak free O-ring sealed high pressure fittings vs. standard compression fittings.

9) Custom build (one piece) large radius 90 degree high pressure fittings connect directly to hoses and components for low flow restriction and ultimate corrosion resistance vs. multiple NPT adaptors with 90 degree standard elbows.

10) Custom engineered pressure vessels guarantied for life, built with glass fiber reinforced Vinyl Ester and stainless steel end plug components. No mix of metals, common with standard pressure vessels.

11)Custom O-ring sealed high pressure ports with threaded backing plates on all pressure vessels. No cracking of plastic endplugs due to over tightened or overloaded NPT high pressure fittings.

12) Premium efficiency high pressure pump motors are epoxy primed and polyurethane top coated vs. single component painted standard motors.

13) All ECHOTec high pressure pump / motor units are anti-vibration mounted with specially engineered soft vibration dampers. This feature dramatically reduces noise transfer into the hull.

Scroll to Top