How 12V Marine Desalination Units Work (Real-World Guide)

A 12V marine desalination unit is one of the simplest ways to produce freshwater on smaller boats without a generator. Here’s how they work and what you can realistically expect on the water.

How Reverse Osmosis Works

All portable watermakers follow this sequence:

  1. A high-pressure pump draws seawater.

  2. The pump forces water through a reverse osmosis membrane.

  3. Salt is rejected.

  4. Freshwater flows into your tank.

  5. Brine is discharged back overboard.

The process is simple, reliable, and ideal for small boats with limited power.

Real-World Power Draw

A typical 12V unit draws 10–25 amps, depending on design.
This pairs well with:

  • Solar setups

  • AGM or lithium house batteries

  • Alternator charging

A system like the Scout SW20 is designed specifically for this power profile.
https://lediwatermaker.com/products/scout-sw20

Water Output Expectations

Factors influencing output include:

  • Water temperature

  • Membrane health

  • Pump efficiency

  • Salinity levels

Expect ~20 L/hr from compact 12V systems in warm Australian water.

Noise, Heat, and Durability

Quality units minimise pump noise and vibration. Look for stainless steel pumps and marine-rated seals — essential for long-term reliability.

When to Choose a 12V Unit

Choose 12V desalination if you want:

  • No generator requirement

  • Low power consumption

  • Lightweight gear

  • Portable freshwater production


FAQ

Can I run a 12V watermaker on solar only?

Yes, with sufficient panel and battery capacity.

How often should I flush the membrane?

After every use for best longevity.

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