Building a custom watermaker installation
Building a custom watermaker installation

Discover why installing a custom watermaker on your boat is essential for long-term cruising and living aboard, providing a reliable source of fresh water from the surrounding seawater.

Building a Custom Watermaker Installation

Welcome to our latest addition to the Boat Modifications and Upgrades section of our blog! In this article, we will be discussing the process of building a custom watermaker installation for your boat. Watermakers, also known as desalination systems, are essential for long-term cruising and living aboard, as they provide a reliable source of fresh water from the surrounding seawater. This guide will walk you through the steps to create a custom watermaker installation that suits your boat and your family’s needs.

Table of Contents

Why Install a Watermaker?

Before diving into the details of building a custom watermaker installation, let’s discuss the reasons why you might want to install a watermaker on your boat in the first place. Here are some of the main benefits of having a watermaker on board:

  1. Self-sufficiency: A watermaker allows you to produce your own fresh water, reducing your reliance on marinas and shore-based water sources. This is particularly important for long-term cruisers and liveaboards who want to explore remote areas and spend extended periods at sea.

  2. Convenience: With a watermaker, you can produce fresh water whenever you need it, without having to worry about rationing your water supply or finding a place to refill your tanks.

  3. Safety: In case of an emergency, a watermaker can be a lifesaver, providing you with a reliable source of fresh water when other sources may not be available.

  4. Water quality: Watermakers produce high-quality, pure water that is free from contaminants and impurities. This can be especially beneficial for those with sensitive skin or allergies, as well as for cooking and cleaning purposes.

Types of Watermakers

There are two main types of watermakers available for boats: reverse osmosis (RO) systems and evaporative systems. Let’s take a closer look at each type:

Reverse Osmosis (RO) Systems

Reverse osmosis is the most common type of watermaker found on boats. These systems work by forcing seawater through a semi-permeable membrane, which filters out salt, minerals, and other impurities. The result is clean, fresh water that is safe to drink and use for other purposes.

RO systems come in a variety of sizes and capacities, ranging from small, portable units to large, high-capacity systems designed for liveaboard boats and long-term cruising. They can be powered by either AC or DC electrical systems, and some models even offer manual operation in case of a power failure.

Evaporative Systems

Evaporative watermakers, also known as distillation units, work by heating seawater to create steam, which is then condensed back into fresh water. These systems are less common on boats, as they tend to be larger, more expensive, and less energy-efficient than RO systems. However, they do have some advantages, such as the ability to produce very high-quality water and the potential for lower maintenance requirements.

Selecting the Right Watermaker for Your Boat

When choosing a watermaker for your boat, there are several factors to consider, including:

  1. Capacity: How much water do you need to produce per day? This will depend on the size of your boat, the number of people on board, and your daily water usage habits. As a general rule, plan for a minimum of 20-30 liters (5-8 gallons) of water per person per day.

  2. Power source: Will you be using an AC or DC electrical system to power your watermaker? Make sure to choose a model that is compatible with your boat’s electrical system.

  3. Space and weight: Consider the size and weight of the watermaker, as well as the available space on your boat for installation. Smaller, more compact units may be more suitable for boats with limited space.

  4. Ease of installation: Some watermakers are easier to install than others, with modular designs and pre-assembled components. If you’re planning to build a custom installation, look for a watermaker that offers flexibility in terms of mounting options and plumbing connections.

  5. Budget: Watermakers can range in price from a few hundred to several thousand dollars, depending on the type, size, and features. Determine your budget and choose a watermaker that offers the best value for your needs.

Installation Considerations

Before you start building your custom watermaker installation, there are several factors to consider in terms of the placement and setup of the system:

  1. Location: Choose a location for your watermaker that is easily accessible for maintenance and troubleshooting, as well as protected from the elements and potential damage. Common installation locations include engine rooms, lazarettes, and dedicated utility spaces.

  2. Ventilation: Ensure that the area where the watermaker is installed has adequate ventilation to prevent overheating and maintain optimal performance.

  3. Plumbing: Plan the plumbing connections for your watermaker, including the intake and discharge lines, as well as the fresh water output. Make sure to use high-quality, marine-grade hoses and fittings to prevent leaks and corrosion.

  4. Electrical: Determine the electrical requirements for your watermaker, including the voltage, amperage, and wiring connections. Use marine-grade electrical components and follow best practices for wiring and circuit protection.

  5. Mounting: Securely mount your watermaker to a solid surface, using appropriate brackets, fasteners, and vibration dampeners to minimize noise and vibration.

Building Your Custom Watermaker Installation

Once you’ve selected the right watermaker for your boat and considered the installation factors, it’s time to start building your custom installation. Here are the general steps to follow:

  1. Assemble the components: Unpack your watermaker and familiarize yourself with the various components, including the membrane housing, pumps, filters, and control panel. Follow the manufacturer’s instructions for any pre-assembly steps, such as installing fittings or mounting brackets.

  2. Install the watermaker: Mount the watermaker in your chosen location, ensuring that it is level and secure. Connect the plumbing lines, including the seawater intake, brine discharge, and fresh water output. Make sure to use appropriate hose clamps and sealants to prevent leaks.

  3. Connect the electrical system: Wire the watermaker to your boat’s electrical system, following the manufacturer’s instructions and best practices for marine electrical installations. Install any necessary circuit breakers, switches, and monitoring devices.

  4. Test the system: Once everything is connected, test your watermaker to ensure that it is functioning properly and producing fresh water. Check for any leaks or issues with the plumbing and electrical connections, and make any necessary adjustments.

  5. Secure and protect: Finally, secure any loose components and protect your watermaker from potential damage, such as by installing protective covers or guards.

Maintenance and Troubleshooting

Regular maintenance is essential for keeping your watermaker running smoothly and efficiently. Here are some general maintenance tips and troubleshooting advice:

  1. Check and replace filters: Regularly inspect the pre-filters and membrane for signs of wear or clogging, and replace them as needed. This will help to maintain optimal water production and prevent damage to the system.

  2. Clean and flush the system: Periodically clean and flush your watermaker to remove any buildup of salt, minerals, or other contaminants. Follow the manufacturer’s recommendations for cleaning and flushing procedures.

  3. Inspect and lubricate pumps: Check the pumps for any signs of wear or damage, and lubricate them as needed to ensure smooth operation.

  4. Monitor system performance: Keep an eye on your watermaker’s performance, such as the water production rate, pressure, and quality. If you notice any changes or issues, troubleshoot the system to identify and resolve the problem.

  5. Winterize the system: If you won’t be using your watermaker for an extended period, such as during the winter months, follow the manufacturer’s instructions for winterizing the system to prevent damage from freezing temperatures or long-term disuse.


Building a custom watermaker installation for your boat can be a rewarding and practical project, providing you with a reliable source of fresh water for your sailing adventures. By carefully selecting the right watermaker for your needs, considering the installation factors, and following the steps outlined in this guide, you can create a custom watermaker installation that will serve you well for years to come. And remember, regular maintenance and troubleshooting are essential for keeping your watermaker running smoothly and efficiently. Happy sailing!