Boat Moisture Absorbers: What To Put In Your Boat

Boats are constantly battling moisture, whether they're in or out of the water. When boats are stored, moisture can cause damage to the interior, and condensation can occur when the air temperature rises and falls. To prevent this, there are a number of moisture-absorbing products available, including electric dehumidifiers and moisture absorber packs. Electric dehumidifiers can be left running 24/7 and will automatically shut down when full. Moisture absorber packs, on the other hand, are often disposable and can simply be thrown away when full.

Electric dehumidifiers

There are a few types of electric dehumidifiers available for boats, each with its own advantages and disadvantages:

• Desiccant dehumidifiers: These use a chemical, usually calcium chloride or Zeolite, to absorb moisture. They have a fan that pulls air into the unit and passes it over a wheel coated with the desiccant chemical, which dries the air. Desiccant dehumidifiers are lightweight, portable, and work better at lower temperatures than compressor dehumidifiers. However, they may use more power and can be more expensive to run.
• Compressor dehumidifiers: These work similarly to air conditioners, cooling the air over coils and condensing the water into a bucket. They are typically quieter and more energy-efficient than desiccant dehumidifiers, but may not be as effective at lower temperatures. Compressor dehumidifiers can also be used with a hose for continuous drainage, which is useful for boat winterization.
• Thermo-electric dehumidifiers: These work without moving parts, using the Peltier Effect to transfer heat between two different metals when an electric current is passed through them. They are quiet, cost-efficient, and lightweight but are slower at removing moisture than other types.

When choosing an electric dehumidifier for your boat, consider the size of the unit, its drying capacity, power consumption, noise level, and any additional features such as tilt switches or remote app control. It is also important to ensure that the unit is designed for marine use and can be safely left unattended, especially if you plan to store your boat for extended periods.

• Ebac AD850E Dehumidifier: This unit is on the higher end price-wise but offers a streamlined design that fits into almost any space on your boat. It has a two-speed fan motor and can operate at 41 degrees, making it ideal for overwinter use. It is quiet and has an automatic shut-off feature to save energy.
• Eva-Dry EVD 22000 Dehumidifier: Small and compact, this unit is perfect for a small boat or RV, or even a single room of a large boat. It offers low energy use and automatically shuts off when at capacity.
• InvisiPure Hydrowave Dehumidifier: This thermo-electric dehumidifier is super quiet and removes up to 27 ounces of moisture per day. It is lightweight and can be easily moved to different areas of the boat. It also has an automatic shut-off feature and can be attached to a hose for continuous draining.
• Ecor Pro Dehumidifier: The Ecor Pro is a stainless steel, compact, and saltwater-resistant unit designed to run 24/7. It is specially designed for marine and water-based use and can be used around pools, spas, and boats of all sizes.
• Meaco Zambezi DD 8L Desiccant Dehumidifier: The Meaco Zambezi is quiet, lightweight, and works down to 33 degrees Celsius. It has a tank and a hose for continuous draining, an anti-mold coating on the tank, a variable humidistat, three fan speeds, and a timer. It also has a sterilizing ionizer that helps to clean the air as it removes humidity.

Hanging moisture absorbers

One such product is the Better Boat hanging moisture absorber, which comes in packs of four. These hanging bags absorb moisture and water from the air, eliminating unwanted smells and controlling moisture in enclosed spaces. They are designed for convenience and can simply be hung and tossed after use.

Another option is the Star Brite No Damp Hanging Bag Moisture Absorber, which can be purchased from Defender. This product is also designed to be hung in enclosed spaces and will help to prevent mould and mildew stains and protect from moisture damage.

In addition to hanging moisture absorbers, there are also refillable moisture absorbers, such as the Refillable Fragrance-Free Moisture Absorber from Fisheries Supply, which can be used to control moisture in your boat.

Non-powered moisture absorbers

There are several non-powered moisture-absorbing products available for boats. These can be particularly useful when your boat is in storage, or if you don't have access to power.

Calcium chloride is a classic moisture absorber. This salt is very hygroscopic, drawing water into itself, and will even dissolve in the water it attracts. It typically absorbs two to three times its weight in water, depending on temperature and relative humidity. Calcium chloride is often found in disposable moisture-absorbing products, such as hanging bags, buckets, and sachets. While calcium chloride can, in theory, be dried and reused, it is usually considered impractical to do so.

Silica gel is another option. This is a reusable moisture absorber that can be dried and reused hundreds of times. Simply bake the silica gel in the oven for a couple of hours to dry it out. However, silica gel has a limited capacity and saturates quickly, so it may not be suitable for long-term storage unless used inside a sealed container or regenerated frequently.

Dri-Z-Air and NoDamp are two further chemical-based desiccants that pull water out of the air. These products capture moisture and combine it with something like calcium chloride to create a non-toxic liquid solution in the bottom of the container.

AquaSorb™ is a premium line of commercial-grade industrial desiccant dehumidifiers. These absorber pouches attract, capture, and convert moisture into crystals, preventing potential mould, mildew, or corrosion. They are safe for all surfaces and can be safely disposed of in the trash. One 500-gram bag treats 36 cubic feet (3’ x 4’ x 3’) and they are available in 4-packs or bulk-packed master cartons.

Eva-Dry offers non-powered moisture absorbers that use a renewable silica gel technology. Over time, the crystals will change from blue to pink, letting you know they've reached their full capacity. At this point, you need to plug the unit into an electrical socket to renew the crystals. After 12 to 15 hours, the crystals will have released the absorbed moisture, and the unit is ready to be used again—for up to 10 years!

Cabin heaters

Types of Cabin Heaters

There are several types of cabin heaters available, including:

• Diesel
• Propane
• Electric

These heaters come in different models depending on how much heat you want, how much power you have available, and the size of your boat.

Recommended Brands

Recommended brands of cabin heaters include:

• Dickinson
• Heatercraft
• King
• Red Dot
• Sig Marine

Portable Electric Heaters

If you're looking for something more portable, there are also portable electric heaters that can be plugged in at the dock. Caframo offers three options:

• TrueNorth: Has a low profile to prevent tipping over and an automatic thermostat to maintain the temperature. It also has an "Anti-Freeze" setting to protect your boat from freezing temperatures.
• DeltaMAX
• Pali: This is an engine compartment heater that protects your engine and bilge from freezing damage. It uses ceramic elements that self-limit to a predetermined temperature to prevent overheating.

Air Dryers

Air dryers are another way to move air around your boat and prevent moisture buildup. Fisheries stocks air dryers from trusted brands.

Air dryers

There are several types of air dryers available, each with its own advantages:

Electric Air Dryers

These devices use electricity to dry the air in enclosed spaces. Examples include the Davis Air Dryr, which comes in two sizes with prices starting at $70, and the Golden Rod Dehumidifier, which has three size options and starts at around $29. West Marine also offers an Air Dryer with Fan for about $100. These electric dryers are ideal for boats, RVs, and cabins, as they efficiently raise the ambient dew point, reducing condensation and preventing mould and mildew.

Absorbent Crystal Air Dryers

This type of air dryer uses absorbent crystals to draw moisture from the air. Star Brite's No Damp Ultra Dome, priced at approximately $18.50, and the Marykate Moisture Control Bag, at about $30, are examples of this variety. These products are excellent for natural or chemical solutions to tackle dampness.

Desiccant Air Dryers

Desiccant air dryers utilise desiccant materials, such as silica gel, to adsorb moisture from the air. They are highly effective in maintaining the efficiency and longevity of compressed air systems by preventing corrosion and damage to pneumatic tools and machinery. While these dryers may require more frequent regeneration, they are ideal for applications that demand extremely dry air, such as pharmaceutical manufacturing or food processing.

Refrigerated Air Dryers

Refrigerated air dryers are the most common type, suitable for general industrial applications. They work by cooling the compressed air to condense and separate moisture, and then reheating the dry air before use. This method effectively suppresses dew point.

Rotary Drum Air Dryers

For industries seeking a consistent dew point without using purge air, rotary drum air dryers are a highly efficient and energy-saving option. They feature a rotating drum with an internal desiccant wheel, allowing simultaneous moisture absorption and regeneration.

Membrane Air Dryers

Membrane air dryers are compact, low-maintenance solutions that use membrane fibres to remove water vapour from compressed air. They are well-suited for point-of-use applications and environments.

Frequently asked questions