SPECTRA Clark Pump Technology | How do marine watermakers recover pressure and reduce power consumption?
When evaluating a watermaker on a boat, the production capacity only answers half the question. The other half is: how much power do the boat's batteries, generators, and renewable energy systems need to expend to produce that fresh water?
Traditional reverse osmosis watermakers must generate high pressure for seawater to pass through the reverse osmosis membrane. After separation, the discharged brine still carries a significant amount of pressure; if this energy is directly returned to the sea, the next batch of seawater must have pressure re-established by the motor.
In 1997, SPECTRA Watermakers introduced the Clark Pump, which precisely changed this long-wasted energy. It recovers the pressure retained in the brine and uses it to drive the next water production cycle, significantly reducing the power demand for marine watermakers performing the same task.
Understanding the Clark Pump in 30 Seconds
What it recovers: The high-pressure energy still retained in the brine after reverse osmosis.
What it provides: According to original manufacturer data, some systems can reduce energy consumption by up to approximately 75% compared to traditional reverse osmosis watermakers.
What it changes: It reduces the load on the vessel's electrical system, allowing batteries, solar, or wind power to support watermaking with suitable models and configurations.
Precise understanding: "Reduces energy consumption by approximately 75%" does not equate to "75% more efficient"; it means the energy required to perform the same watermaking task is significantly reduced.
Where is energy consumed in traditional watermakers?
The salinity of seawater creates high osmotic pressure. A reverse osmosis system must push seawater through the membrane with high pressure for water molecules to pass, while salts and other dissolved solids remain on the brine side.
Traditional systems typically use a high-pressure pump to continuously generate this pressure; after separation, the concentrated brine is discharged through a throttling valve, and the residual pressure is lost. The high-pressure pump must therefore constantly re-supply the energy needed for the next cycle.
Clark Pump: Returning Brine Pressure to the System
The Clark Pump hydraulically connects the brine end with the incoming seawater end. The pressure still retained in the brine after leaving the reverse osmosis membrane is no longer wasted directly, but instead drives an internal piston in the pump, helping the next batch of incoming water build the pressure required for reverse osmosis.
A low-pressure feed pump is still responsible for delivering seawater into the system, but a significant portion of the energy-intensive high-pressure work is completed by the recovered pressure. This is key to SPECTRA's ability to maintain practical water production at lower power.
The feed pump consistently delivers pre-filtered seawater into the system.
The concentrated brine drives the Clark Pump piston, transferring existing pressure to the incoming fresh seawater.
High-pressure seawater enters the membrane housing, producing two streams: fresh water and concentrated brine.
The concentrated brine transfers its pressure to the next cycle again before being discharged overboard.
Why is this technology particularly suitable for vessels?
Sailboats and long-distance cruising vessels have limited energy budgets. Navigation instruments, refrigerators, autopilots, lighting, communications, and living equipment all use the same power supply; if a watermaker requires a large high-pressure motor to run for extended periods, it directly impacts battery capacity, charging time, and generator run hours.
The Clark Pump ensures that water production no longer relies entirely on high-power high-pressure pumps. For boat owners, the value is not abstract "power saving," but rather obtaining more fresh water with existing power, and reducing situations where watermaking competes with other onboard equipment.
Actual energy planning still depends on the model: SPECTRA's different series use 12V, 24V, 48V DC, or AC power. Whether solar, wind, or battery can support daily water production needs must be calculated based on the model's power, estimated operating time, available battery capacity, and actual charging conditions.
Clark Pump vs. Pearson Pump: Different Positions
The Clark Pump primarily serves small to medium-sized low-energy watermaking systems. When production volume and flow demands increase, SPECTRA adopts the Pearson Pump based on the product architecture. Both focus on recovering brine pressure, but they are not simply a high-low tier relationship; rather, they correspond to different flow rates, production scales, and task requirements.
System Automatically Maintains Operating Conditions When Water Temperature and Salinity Change
Water temperature and salinity in different sea areas can alter the pressure required for reverse osmosis. SPECTRA's official documentation states that the hydraulic design of the Clark Pump and Pearson Pump allows them to adapt their operating status to changes in incoming water conditions, eliminating the need for users to continuously manually adjust traditional high-pressure valves.
This feature is particularly important for cross-sea voyages. When a watermaker moves from warm coastal waters to colder seas, or encounters water with different salinity, the operating procedure remains consistent, reducing the risk of incorrectly setting pressure.
The Real Advantage Lies in the Entire System Working Together
While the Clark Pump is important, a reliable marine watermaker still includes water intake, pre-filtration, feed pump, reverse osmosis membrane, salinity sensor, product water switching, freshwater flush, and control system. Incorrect installation or maintenance of any component can affect final water production and membrane lifespan.
Therefore, when choosing SPECTRA, one should not just compare individual pumps. The vessel type, daily water demand, existing power, installation space, maintenance access, and cruising area must all be evaluated as part of an integrated plan.
Learn about SPECTRA Watermakers water production equipment
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SPECTRA Watermakers: Our Technology
SPECTRA Watermakers: Manuals, Specifications, Piping Diagrams, and Wiring Diagrams Download