Installing a pre-filter system for your watermaker
Installing a pre-filter system for your watermaker

Ensure the longevity and efficiency of your watermaker and enjoy clean, fresh water on your sailing adventures by installing a pre-filter system.

Installing a Pre-Filter System for Your Watermaker

As you embark on your sailing adventure, one of the most essential systems on your boat is the watermaker. A watermaker is a device that converts seawater into potable water through a process called desalination. This is crucial for long-term cruising, as it allows you to have a reliable source of fresh water without having to rely on shore-based water supplies.

One of the key components of a watermaker is the pre-filter system. This system is responsible for removing larger particles and debris from the seawater before it enters the main desalination unit. In this article, we will discuss the importance of a pre-filter system, the different types of pre-filters available, and how to install one on your boat.

Why You Need a Pre-Filter System

A pre-filter system is essential for the proper functioning and longevity of your watermaker. Seawater contains a wide range of particles, including sand, silt, algae, and other organic matter. If these particles are not removed before the water enters the desalination unit, they can cause damage to the delicate membranes and other components of the system.

By installing a pre-filter system, you can significantly reduce the risk of damage to your watermaker and ensure that it operates efficiently for a longer period. Additionally, a pre-filter system can help improve the taste and quality of the water produced by your watermaker, as it removes many of the impurities that can affect the water’s flavor.

Types of Pre-Filters

There are several types of pre-filters available for watermakers, each with its own advantages and disadvantages. The most common types include:

Sediment Filters

Sediment filters are designed to remove larger particles, such as sand and silt, from the water. They are typically made from pleated or spun polypropylene and are available in various micron ratings. The lower the micron rating, the smaller the particles the filter can remove. For example, a 20-micron filter will remove particles larger than 20 microns in size.

Sediment filters are relatively inexpensive and easy to replace, making them a popular choice for pre-filter systems. However, they can become clogged quickly in areas with high levels of particulate matter, requiring frequent replacement.

Activated Carbon Filters

Activated carbon filters are designed to remove organic compounds, chlorine, and other chemicals from the water. They work by adsorbing these contaminants onto the surface of the activated carbon, effectively trapping them and preventing them from passing through the filter.

Activated carbon filters can help improve the taste and odor of the water produced by your watermaker. However, they are not as effective at removing larger particles and may need to be used in conjunction with a sediment filter for optimal performance.

Dual-Stage Pre-Filter Systems

A dual-stage pre-filter system combines both a sediment filter and an activated carbon filter in a single unit. This allows for more comprehensive filtration, as the sediment filter removes larger particles while the activated carbon filter targets chemicals and organic compounds.

Dual-stage pre-filter systems are more expensive than single-stage systems but offer better overall performance and protection for your watermaker.

Installing a Pre-Filter System

Now that you understand the importance of a pre-filter system and the different types available, it’s time to install one on your boat. Follow these steps to ensure a successful installation:

1. Choose the Right Pre-Filter System

Select a pre-filter system that is compatible with your watermaker and meets your specific needs. Consider factors such as the type of water you will be sailing in (e.g., coastal waters with high levels of sediment or open ocean with fewer particles), the desired water quality, and your budget.

2. Determine the Installation Location

Find a suitable location for the pre-filter system on your boat. Ideally, it should be close to the watermaker and easily accessible for filter replacement and maintenance. Ensure that there is enough space for the pre-filter housing, as well as any additional components such as mounting brackets and hoses.

3. Install the Pre-Filter Housing

Mount the pre-filter housing to a secure surface using the provided brackets or other suitable hardware. Make sure the housing is level and properly aligned to allow for easy filter replacement and maintenance.

4. Connect the Hoses

Connect the inlet hose from the seawater source (e.g., a through-hull fitting or sea strainer) to the inlet port on the pre-filter housing. Similarly, connect the outlet hose from the pre-filter housing to the inlet port on your watermaker. Use high-quality, reinforced hoses and secure them with stainless steel hose clamps to prevent leaks and ensure a reliable connection.

5. Install the Filter Cartridges

Insert the appropriate filter cartridges (e.g., sediment filter, activated carbon filter, or both) into the pre-filter housing according to the manufacturer’s instructions. Make sure the cartridges are properly seated and secure before closing the housing.

6. Test the System

Turn on your watermaker and check for any leaks or issues with the pre-filter system. Monitor the water pressure and flow rate to ensure that the pre-filter is not causing any restrictions or performance issues. If necessary, adjust the system or consult the manufacturer for assistance.

Maintaining Your Pre-Filter System

To keep your pre-filter system functioning optimally, it’s essential to perform regular maintenance and replace the filter cartridges as needed. The frequency of replacement will depend on the type of filters used and the water conditions in your sailing area.

As a general rule, sediment filters should be replaced every 3-6 months or when the pressure drop across the filter becomes significant. Activated carbon filters should be replaced every 6-12 months or when the taste and odor of the water begin to deteriorate.

By maintaining your pre-filter system and ensuring that it is functioning correctly, you can protect your watermaker, extend its lifespan, and enjoy clean, fresh water on your sailing adventures.


Installing a pre-filter system for your watermaker is a crucial step in ensuring the longevity and efficiency of your desalination unit. By understanding the different types of pre-filters available and following the proper installation and maintenance procedures, you can enjoy the benefits of a reliable source of fresh water while exploring the open sea with your family.