Selecting a yacht watermaker by litres per hour alone leaves several questions unanswered. The plant must match actual water demand, available operating hours, feed-water conditions, electrical capacity and the physical installation.
This guide explains how to build a practical capacity requirement, compare AC and DC options, assess energy recovery and identify installation issues before ordering equipment. It also uses published Sea Recovery, Spectra and Schenker specifications to show the range of available outputs.
Build the requirement from actual water use
Start with the number of people aboard and how they use water. Yacht length does not establish demand because crew numbers, guest use, itinerary and climate can differ substantially between vessels of similar size.
Spectra gives a general recommendation of 5 to 20 US gallons per person per day. Treat that as a planning range rather than selecting one figure without checking the vessel's operation.
Prepare a demand log covering:
- People aboard: Separate normal crew demand from periods with guests aboard.
- Showers: Record the demand created by the vessel's expected daily routine.
- Laundry: Include the planned laundry schedule rather than treating it as an occasional extra.
- Deck washing: Account for water used outside the accommodation.
- Guest use: Compare normal operation with the higher-use periods expected during the itinerary.
The result should be a documented daily requirement. It can then be compared with the hours during which the watermaker can realistically operate and the production measured during commissioning.
Match litres per hour to planned run time
A watermaker's hourly output only becomes useful when paired with an operating schedule. Spectra says many owners run their plants for three to four hours at a time, with a maximum of 12 hours per day.
Use the run window the yacht can actually support. Do not base the selection on continuous operation if the charging plan, generator schedule or yacht routine will not provide that operating time.
Published capacities show how widely systems differ. The Sea Recovery range includes small-yacht and higher-demand equipment, while Schenker watermakers include energy-recovery models with different voltage and wattage specifications.
| Range or model | Nominal production | Electrical specification | Selection context |
|---|---|---|---|
| Sea Recovery Aqua Whisper Mini | 27, 55, 87 or 117 L/h | Model-specific | Small-yacht reference point |
| Sea Recovery Aqua Matic XL | 8,300 to 12,000 L/day | Model-specific | Midsize to large leisure boats |
| Spectra DC range | 24.6 to 1,590 L/h | Designed for 12/24 V batteries | Low-voltage range |
| Spectra Ventura 150C | More than 24 L/h | 24 V | Concrete small-system example |
| Schenker Zen 30 | 30 L/h | 110 W, 12/24 VDC | Energy-recovery model |
| Schenker Zen 100 | 100 L/h | 400 W, 12/24/48 VDC or AC | DC or AC option |
These figures are comparison points, not guaranteed production in every sea condition. EchoTec states that reverse-osmosis performance varies with feed-water temperature and salinity. Its DML range, for example, is rated at 26°C and 33 g/L NaCl, so the conditions behind any quoted output matter.
Choose between AC, DC and energy recovery
Check the yacht's available electrical supply before settling on capacity. The assessment should include the DC or AC source, charging strategy, generator strategy and the selected model's voltage and wattage.
Some low-voltage systems are intended for battery-based designs. Spectra says its DC range is designed for 12/24 V batteries, while the 24 V Ventura 150C produces more than 24 litres per hour. Schenker lists the Zen 30 at 110 W and 12/24 VDC, and the Zen 100 at 400 W with 12/24/48 VDC or AC.
Energy recovery changes how the high-pressure load is handled. Spectra describes a design that transfers pressure from the brine stream to incoming water, avoiding the energy penalty of conventionally pressurising the entire seawater flow. Schenker's Zen range is also an energy-recovery option, with listed capacities from 30 to 300 L/h across its single and twin models.
Individual model voltage and wattage still need checking. Where the installation involves high-current cabling, AC/DC conversion or generator-load assessment, involve an engineer and assess the yacht's marine electrical system as part of the project.
Check space, intake and feed-water conditions
Reverse osmosis needs prefiltration and high pressure. Sea Recovery describes seawater passing through semi-permeable membranes at about 60 bar after prefiltering, with optional post-treatment including pH neutralisation or UV.
The installation therefore needs more than enough space for the main unit. Spectra requires a dry, ventilated and accessible location, including access for cartridge-filter changes. It also warns against sharing the intake through-hull with other equipment.
The intake needs particular attention on a high-speed or planing yacht. Spectra warns that high hull-water velocity can create a vacuum and accelerate pump wear. Underway operation and intake placement should be assessed rather than assumed to be benign.
Feed-water conditions also belong in the commissioning record. Temperature and salinity affect production, so record them alongside pressure, product flow and power draw. That provides a measured operating reference for the installed plant rather than relying only on nominal output.
What crew can check safely
Crew can collect the operating information needed for selection without modifying the watermaker or its electrical and seawater systems.
- Prepare a demand log: Record people aboard, showers, laundry, deck washing and guest use. Compare daily demand with actual operating hours and measured water production.
- Review available services: Check whether the yacht has the required DC or AC supply and how the selected operating period fits the charging or generator strategy.
- Inspect the proposed location: Confirm that it is dry, ventilated and accessible, with practical access for cartridge-filter changes.
- Review the intake proposal: Identify the through-hull location and confirm that the design does not assume a shared intake with other equipment.
- Record commissioning data: Note temperature, salinity, pressure, product flow and power draw. Keep the readings tied to the conditions in which they were recorded because output varies with temperature and salinity.
When to call an engineer
Some choices affect the yacht's electrical distribution, tanks, hull fittings or control arrangements. These should be resolved before equipment is ordered.
Call an engineer when:
- A new seawater intake is required: The design may involve a dedicated through-hull and safe below-waterline or inlet arrangements.
- Electrical changes are needed: High-current cabling, AC/DC conversion and generator-load assessment need to be included in the installation plan.
- Tank or control work is involved: Tank modification or product-water diversion controls make the project more than a simple equipment replacement.
- The proposed location is unsuitable: A space that cannot meet the specified dry, ventilated and accessible requirements needs a different installation design.
- The yacht is high-speed or planing: Intake position and proposed underway operation require an engineering assessment because hull-water velocity can create a vacuum and accelerate pump wear.
Blueward Marine can assess capacity, electrical supply, intake placement and installation access through its yacht watermaker service. To send fault details and photos, use the online technical booking form; for an urgent fault in Mallorca, call the 24/7 line on +34 971 251 374.
Frequently asked questions
How big should a yacht watermaker be?
Start with documented water demand rather than yacht length. Spectra gives a general guide of 5 to 20 US gallons per person per day, with crew, itinerary and climate affecting the requirement. Match that demand against realistic operating periods, which Spectra describes as three to four hours at a time or a maximum of 12 hours per day.
Can a yacht watermaker run from batteries or solar?
Some low-voltage, energy-recovery systems may suit a battery or solar design. Spectra says its DC range is designed for 12/24 V batteries. Schenker specifies its Zen 30 at 110 W and 12/24 VDC. Check the selected model's voltage and wattage against the vessel's charging strategy, available supply and planned operating hours.
Why can actual watermaker output differ from the brochure?
Feed-water temperature and salinity affect reverse-osmosis performance. EchoTec rates its DML range at 26°C and 33 g/L NaCl, so its quoted output is tied to those conditions. During commissioning, record temperature, salinity, pressure, product flow and power draw to establish how the installed system performs under the vessel's actual operating conditions.
Sources and further reading
These references informed this guide. Follow the procedures and limits for the equipment installed on board.