Marine water makers primarily work by using a process called reverse osmosis to turn saltwater into fresh, potable water.
Understanding the Process: Reverse Osmosis
At its core, a marine water maker utilizes reverse osmosis to remove dissolved salts and impurities from seawater. Unlike standard filtration, which separates larger particles, reverse osmosis uses pressure to push water through a highly selective membrane.
Here's a breakdown of the process:
- Pre-filtration: Seawater is typically passed through pre-filters first. This step removes larger sediments, sand, and other particles that could damage the high-pressure pump or clog the delicate reverse osmosis membrane.
- Pressurization: The filtered saltwater is then subjected to significant pressure. As the reference states, reverse osmosis marine water makers produce fresh water by pressurizing salt water to around 800psi. This high pressure is crucial to overcome the natural osmotic pressure that would otherwise prevent pure water from moving out of the concentrated salt solution.
- Membrane Separation: The highly pressurized saltwater is forced against a semi-permeable membrane. This membrane acts like a very fine filter. Forcing it through a semi-permeable membrane (a very small filter screen) allows pure water molecules to pass through.
- Impurity Rejection: The key characteristic of the semi-permeable membrane is that practically all contaminants such as salt, bacteria, viruses and grit are left behind. These rejected impurities, along with some concentrated saltwater (often called brine or reject water), are flushed away.
- Freshwater Collection: The pure water that successfully passes through the membrane is collected as fresh water, ready for use on the boat.
Key Components
A typical marine water maker system includes:
- Pre-filters: To protect the main components.
- High-Pressure Pump: Generates the high pressure needed for reverse osmosis (around 800psi for seawater).
- Membrane Housing: Contains the semi-permeable membrane(s).
- Semi-Permeable Membrane: The core element that separates water from salts and contaminants.
- Control System: Manages pressure, flow rates, and monitors the process.
- Post-filtration/Treatment (Optional): Some systems may include post-filters or UV sterilizers for added water quality assurance.
| Input | Process | Output | Rejected Items |
|---|---|---|---|
| Saltwater | High-Pressure Reverse Osmosis (≈800psi) | Freshwater | Salt, Bacteria, Viruses, Grit, etc. |
By effectively forcing water molecules through a microscopic barrier while leaving impurities behind, marine water makers provide a reliable source of fresh water for cruising yachts and other vessels.
