Watermakers / Compare systems / How much water
How much water do you need?
Output per hour, times the hours you'll run it. Here's how our systems compare, and how to work out what your crew needs.
Output Per Day
Litres per hour, times the hours you run it.
| System | Output | 1 hour a day | 2 hours a day | 3 hours a day |
|---|---|---|---|---|
| DC High-Output | 70 L/h | 70 L | 140 L | 210 L |
| Engine Drive or AC, 1 membrane | 80 L/h | 80 L | 160 L | 240 L |
| High-output short vessel | 115 L/h | 115 L | 230 L | 345 L |
| Engine Drive or AC, 2 membranes | 160 L/h | 160 L | 320 L | 480 L |
| Engine Drive or AC, 3 membranes | 240 L/h | 240 L | 480 L | 720 L |
Rated output, with seawater at 25 °C and 35,000 ppm.
How much does your crew use?
It depends on how you live aboard: drinking and cooking, showers, dishes and rinsing gear.
The most reliable number is your own. Note what you use over a week aboard, then size for that, with some to spare.
What changes the output?
- Water temperature and salinity. Our figures are for 25 °C seawater at 35,000 ppm, so expect less in colder or saltier water.
- Membrane age. Water quality changes as the membrane ages: about 120 ppm total dissolved solids when new, about 300-400 ppm at 3-4 years.
- Filters. A dirty seawater filter cuts the flow. Clean or replace it as part of your routine.
Start small, add later
Engine-driven and AC systems start at 80 L/h with one membrane, and take a second or third to reach 160 or 240 L/h. Adding a second or third membrane.
Already have a system? Measure its real output with a measuring cup and a stopwatch.
Talk to us about your boat
Tell us how your boat is powered and how much water you use. Pete will point you at the right setup.