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DC Watermakers - Frequently Asked Questions (FAQs)

A couple on a typical cruising boat requires a minimum of 8 gallons or 30 Liters. per day for drinking, laundry, showers and washing dishes if water is used very conservatively. Common conservation methods are: Using foot pumps versus pressurized fresh water (at least in the galley), taking saltwater showers and rinse with fresh water, pre-rinsing dishes with seawater, washing fruits and vegetables with saltwater and substitute fresh water with saltwater for cooking where possible.

Wash downs of deck and equipment after passages and a more relaxed water consumption will require about 13 gallons or 50 Liters. per day per couple.

Boaters often regret that they initially did not install a larger system. A good rule is to fit the largest system you can afford and install without compromising valuable storage space. Larger systems make better use of times when surplus energy is available and run less often, therefore requiring less maintenance and pre-filtration cost.

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

Depending on the model, you will need to provide 20 to 38 amps at 12.5 V DC during one hour of operation. Larger systems draw more but are also more practical as they can produce your fresh water demand in shorter time.

Since most “watermaking” is done while the engine is running or solar/wind charging is at its peak, energy efficiency is less critical than the fresh water output.

Remember, your alternator’s regulator allows full charging power only when the batteries are low discharged and only for a short time. After the initial bulk charge, the watermaker runs on the surplus power.

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.

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. Against common belief; the booster pump is not needed for the fresh water flush procedure as the required pressure is created by the boats’ fresh water supply pump.

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.

The newly developed post treatment system returns some hardness to the water to combat this problem. Rather than incorporating finicky and maintenance intensive energy recovery pumps to increase energy efficiency at the cost of reliability and increased purchase price, ECHOTec is the first watermaker manufacturer to offer a practical, low maintenance solution that saves up to 50% fresh water by improving the RO product quality.

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.

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, if you leave your boat unattended you must turn off the main battery switch; 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 DC 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.

Bilge pumps should be directly connected to the batteries. There are divided opinions whether the pumps should be fused or not.

For your peace of mind, disconnect your batteries and 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 systems like the ECHOTec DML 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 ranging from 36 to 41 ppt.

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.

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.

The pH buffer/hardener post treatment system is developed by ECHOTec and replacement cartridges are presently not available anywhere else.

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

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.

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

ECHOTec watermakers are the quietest triplex plunger pump desalinators in the world.

They are about 10 dB quieter than other brands on the market.

The system 260-DML-1 creates even less noise. Due to its very low pump RPM it runs with a negligible hum.

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) Patented spring loaded automatic pressure regulators with single O-ring seal for constant flow and superior reliability vs. needle valves with packing.

2) 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.

3) ECHOTec is the only 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.

4) 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.

5) 316 stainless control panels vs. painted or anodized aluminum panels that easily corrode in contact with stainless gauges and valves (no mix of metals).

6) 316 stainless steel filter housing brackets for ultimate corrosion resistance vs. painted aluminum or mild steel.

7) Stainless steel high pressure pump heads for ultimate corrosion resistance, guaranteed for life.

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

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

10) 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.

11) Custom engineered pressure vessels guarantied for life, built with glass fiber reinforced epoxy and Duplex end plug components. No stainless steel bolts or retaining rings seize or crack in contact with supporting aluminum parts, common with standard GRP/aluminum/316SS vessels.

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

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

14) 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.

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