Marine Water Tanks

These NSF and FDA compliant marine water storage tanks are made to be incredibly strong, nearly unbreakable, and are very affordable. Plastic marine water tanks (poly) are available in nearly every size and shape. Made from one piece of thick poly, there are no seams so less opportunity for leaking, and made with a rotomold process for superior strength. You won’t find better-made marine fresh water tanks for the price. 

Made from one piece to form 3/8” thick walls using a roto-mold process to create a seamless holding tank superior in strength and performance. These custom fitted marine water tanks are built to go the distance.   

*Note: Customize the placement of the fittings when you place the order.  We spin-weld the fittings to ensure your holding tank is securely connected to your plumbing.

  • Complies with NSF 61, FDA Reg CFR 177.1520, and Coast Guard Standards
  • Made from virgin polyethylene (poly) resins
  • Seamless tank made from one piece (less likely to break or leak)
  • 3/8” thick tank walls
  • Customized fitting placement
  • Spin weld fittings
  • Outlasts the competition

For use as marine water tanks, marine fresh water tanks, plastic marine water tanks, poly marine water tanks, custom marine water tanks, and more!

We have 100’s of sizes ranging from 2 gallons, 40 gallons, 50 gallons, 100 gallon marine water tanks.  They range in size up to 250 gallons for these poly marine fresh water tanks.

Looking for something else? Chances are, we have it, and at affordable prices too!  Just call us and ask!

Pick the size and shape you need from the list. Mark up the drawing with your fittings placement. Call us with any questions!

Shop by Category

Marine Water Tanks

  • An image of a 65 Gallon Marine Holding Tank | B324

    33 Gallon Marine Fresh Water Tank | B397

    The 33 Gallon Marine Fresh Water Tank offered by One Clarion is a versatile and portable solution for your marine water storage needs. With its rectangular shape, this tank is designed to fit easily in your boat or other marine vessel. Made from durable...

    $432.83
    Add to Cart
  • 33 Gallon Marine Water Tank MW-558. Technical drawing of a polyethylene water tank designed for marine vessels.

    33 Gallon Marine Water Tank MW-558

    This tank ships in 6-8 weeks. Custom fitting placement is not available at this time. It can be ordered blank, or blank with a DIY Fitting Kit Custom Roto-Mold 33 Gallon Marine Water Tank, Part# MW-558, is engineered to meet the requirements of mobile...

    MSRP: $311.82
    $296.48
    Add to Cart
  • 33 Gallon Marine Water Tank MW-525. Technical drawing of a polyethylene water tank designed for marine vessels.

    33 Gallon Marine Water Tank MW-525

    This tank ships in 6-8 weeks. Custom fitting placement is not available at this time. It can be ordered blank, or blank with a DIY Fitting Kit Custom Roto-Mold 33 Gallon Marine Water Tank, Part# MW-525, is engineered to meet the requirements of mobile...

    MSRP: $325.47
    $309.44
    Add to Cart
  • 33 Gallon Marine Water Tank MW-332. Technical drawing of a polyethylene water tank designed for marine vessels.

    33 Gallon Marine Water Tank MW-332

    This tank ships in 6-8 weeks. Custom fitting placement is not available at this time. It can be ordered blank, or blank with a DIY Fitting Kit Custom Roto-Mold 33 Gallon Marine Water Tank, Part# MW-332, is engineered to meet the requirements of mobile...

    MSRP: $364.83
    $346.87
    Add to Cart
  • 33 Gallon Marine Water Tank MW-30. Technical drawing of a polyethylene water tank designed for marine vessels.

    33 Gallon Marine Water Tank MW-30

    This tank ships in 6-8 weeks. Custom fitting placement is not available at this time. It can be ordered blank, or blank with a DIY Fitting Kit Custom Roto-Mold 33 Gallon Marine Water Tank, Part# MW-30, is engineered to meet the requirements of mobile...

    MSRP: $306.32
    $291.24
    Add to Cart
  • 33 Gallon Marine Water Tank MW-237. Technical drawing of a polyethylene water tank designed for marine vessels.

    33 Gallon Marine Water Tank MW-237

    This tank ships in 6-8 weeks. Custom fitting placement is not available at this time. It can be ordered blank, or blank with a DIY Fitting Kit Custom Roto-Mold 33 Gallon Marine Water Tank, Part# MW-237, is engineered to meet the requirements of mobile...

    MSRP: $286.30
    $272.21
    Add to Cart
  • An image of a 40 Gallon Marine Fresh Water Tank | B439

    34 Gallon Marine Fresh Water Tank | B538

    The 34 Gallon Marine Fresh Water Tank by One Clarion is a rectangular-shaped portable tank designed for above ground use. This tank is made of high-quality polyethylene material in natural white color. It measures 26 inches in length, 22 inches in width,...

    $502.11
    Add to Cart
  • An image of a 68 Gallon RV Holding Tank | RV80H

    34 Gallon Marine Fresh Water Tank | B471

    Introducing the 34 Gallon Marine Fresh Water Tank by One Clarion. This portable tank is designed specifically for marine use, making it the perfect solution for your fresh water needs while out on the water. With a rectangular shape and a capacity of 34...

    $466.97
    Add to Cart
  • An image of a 50 Gallon Marine Holding Tank | BOAT8W

    34 Gallon Marine Fresh Water Tank | B381

    The 34 Gallon Marine Fresh Water Tank from One Clarion is a rectangular, portable tank designed for above ground use. Made from polyethylene in a natural white color, this tank is 34" in length, 26" in width, and 9 1/2" in height. It is not designed for...

    $350.48
    Add to Cart
  • Image of a 34 Gallon Trionic Marine Fresh Water Tank

    34 Gallon Trionic Marine Fresh Water Tank | WH-2034

    The 34 Gallon Trionic Marine Fresh Water Tank is a portable and above ground water tank designed specifically for marine use. Its rectangular shape allows for easy installation and placement on boats or other water vessels. Made from durable polyethylene...

    $492.07
    Add to Cart
  • 34 Gallon Marine Water Tank MW-482. Technical drawing of a polyethylene water tank designed for marine vessels.

    34 Gallon Marine Water Tank MW-482

    This tank ships in 6-8 weeks. Custom fitting placement is not available at this time. It can be ordered blank, or blank with a DIY Fitting Kit Custom Roto-Mold 34 Gallon Marine Water Tank, Part# MW-482, is engineered to meet the requirements of mobile...

    MSRP: $323.90
    $307.95
    Add to Cart
  • 34 Gallon Marine Water Tank MW-234. Technical drawing of a polyethylene water tank designed for marine vessels.

    34 Gallon Marine Water Tank MW-234

    This tank ships in 6-8 weeks. Custom fitting placement is not available at this time. It can be ordered blank, or blank with a DIY Fitting Kit Custom Roto-Mold 34 Gallon Marine Water Tank, Part# MW-234, is engineered to meet the requirements of mobile...

    MSRP: $393.45
    $374.09
    Add to Cart
  • An image of a 12 Gallon Marine Fresh Water Tank | B441

    35 Gallon Marine Fresh Water Tank | BOAT7W

    Introducing the 35 Gallon Marine Fresh Water Tank by One Clarion. This portable tank is perfect for marine environments and is designed to be used above ground. With its rectangular shape and dimensions of 30" length x 22" width x 14" height, it provides...

    $362.53
    Add to Cart
  • An image of a 25 Gallon Marine Fresh Water Tank | B180

    35 Gallon Marine Fresh Water Tank | BOAT6W

    Introducing the 35 Gallon Marine Fresh Water Tank by One Clarion. This portable tank is perfect for marine environments and is designed to be used above ground. With its rectangular shape, it offers a spacious capacity of 35 gallons. Made from...

    $362.53
    Add to Cart
  • An image of a 9 Gallon Marine Holding Tank | B341

    35 Gallon Marine Fresh Water Tank | BOAT38W

    Introducing the 35 Gallon Marine Fresh Water Tank by One Clarion. This portable tank is perfect for marine environments and is designed to be used above ground. With its rectangular shape, it offers a spacious capacity of 35 gallons. Made from...

    $362.53
    Add to Cart
  • An image of a 10 Gallon Marine Holding Tank | B365

    35 Gallon Marine Fresh Water Tank | BOAT1W

    Introducing the 35 Gallon Marine Fresh Water Tank by One Clarion. This portable tank is specifically designed for marine use, making it perfect for boats and other water vessels. With its rectangular shape, it can easily fit into tight spaces and...

    $339.43
    Add to Cart
  • An image of a 32 Gallon RV Fresh Water Tank | RVB316

    35 Gallon Marine Fresh Water Tank | B460

    The 35 Gallon Marine Fresh Water Tank by One Clarion is a rectangular-shaped portable tank designed for above ground use. This tank is made of polyethylene material and comes in a natural white color. It measures 36 1/2" in length, 37 3/8" in width, and...

    $515.18
    Add to Cart
  • An image of a 5 Gallon Marine Fresh Water Tank | B268

    35 Gallon Marine Fresh Water Tank | B445

    Introducing the 35 Gallon Marine Fresh Water Tank by One Clarion. This portable tank is perfect for marine environments and is designed to be used above ground. With its rectangular shape, it offers a spacious capacity of 35 gallons. Made from...

    $492.07
    Add to Cart
  • An image of a 65 Gallon RV Fresh Water Tank | B248

    35 Gallon Marine Fresh Water Tank | B431

    The 35 Gallon Marine Fresh Water Tank by One Clarion is a rectangular-shaped portable tank designed for above ground use. This tank is made of polyethylene material and comes in a natural white color. It measures 54 inches in length, 16 inches in width,...

    $492.07
    Add to Cart
  • An image of a 25 Gallon Marine Holding Tank | B171

    35 Gallon Marine Fresh Water Tank | B371

    Introducing the 35 Gallon Marine Fresh Water Tank by One Clarion. This portable tank is perfect for marine environments and is designed to be used above ground. With its rectangular shape, it offers a generous capacity of 35 gallons. Made from...

    $421.77
    Add to Cart
  • An image of a 11 Gallon Marine Fresh Water Tank | B286

    35 Gallon Marine Fresh Water Tank | B203

    Introducing the 35 Gallon Marine Fresh Water Tank by One Clarion. This portable tank is perfect for marine environments and is designed to be used above ground. With its rectangular shape and dimensions of 48" length x 17" width x 13 3/4" height, it...

    $480.02
    Add to Cart
  • An image of a 7 Gallon Marine Holding Tank | B287

    35 Gallon Marine Fresh Water Tank | B147

    One Clarion is proud to present the 35 Gallon Marine Fresh Water Tank. This marine water tank is designed in a rectangular shape, making it easy to fit into any space. Its portable nature allows for convenient transportation, while its above ground...

    $350.48
    Add to Cart
  • An image of a 9 Gallon Marine Holding Tank | B442

    35 Gallon Marine Fresh Water Tank | B116

    Upgrade your marine vessel with the 35 Gallon Marine Fresh Water Tank from One Clarion. This rectangular tank is designed for portability and is suitable for above ground use. Made from polyethylene in a natural white color, this tank measures 28" in...

    $362.53
    Add to Cart
  • Image of a 35 Gallon Trionic Marine Fresh Water Tank

    35 Gallon Trionic Marine Fresh Water Tank | WH-2035-1

    The 35 Gallon Trionic Marine Fresh Water Tank is a versatile and portable solution for your marine water storage needs. With its rectangular shape, this tank is designed to fit easily in any above ground environment. Made from high-quality polyethylene,...

    $492.07
    Add to Cart
  • 35 Gallon Marine Water Tank MW-412. Technical drawing of a polyethylene water tank designed for marine vessels.

    35 Gallon Marine Water Tank MW-412

    This tank ships in 6-8 weeks. Custom fitting placement is not available at this time. It can be ordered blank, or blank with a DIY Fitting Kit Custom Roto-Mold 35 Gallon Marine Water Tank, Part# MW-412, is engineered to meet the requirements of mobile...

    MSRP: $378.50
    $359.86
    Add to Cart
  • 35 Gallon Marine Water Tank MW-363. Technical drawing of a polyethylene water tank designed for marine vessels.

    35 Gallon Marine Water Tank MW-363

    This tank ships in 6-8 weeks. Custom fitting placement is not available at this time. It can be ordered blank, or blank with a DIY Fitting Kit Custom Roto-Mold 35 Gallon Marine Water Tank, Part# MW-363, is engineered to meet the requirements of mobile...

    MSRP: $479.51
    $455.91
    Add to Cart
  • 35 Gallon Marine Water Tank MW-322. Technical drawing of a polyethylene water tank designed for marine vessels.

    35 Gallon Marine Water Tank MW-322

    This tank ships in 6-8 weeks. Custom fitting placement is not available at this time. It can be ordered blank, or blank with a DIY Fitting Kit Custom Roto-Mold 35 Gallon Marine Water Tank, Part# MW-322, is engineered to meet the requirements of mobile...

    MSRP: $309.25
    $294.02
    Add to Cart
  • An image of a 42 Gallon Marine Holding Tank | B443

    36 Gallon Marine Fresh Water Tank | B478

    Introducing the 36 Gallon Marine Fresh Water Tank by One Clarion. This portable tank is perfect for marine environments and is designed to be used above ground. With its rectangular shape, it offers a spacious capacity of 36 gallons, providing ample...

    $362.53
    Add to Cart
  • An image of a 7 Gallon RV Fresh Water Tank | RVB275

    36 Gallon Marine Fresh Water Tank | B428

    Introducing the 36 Gallon Marine Fresh Water Tank by One Clarion. This portable tank is specifically designed for marine use, making it perfect for boating and other water activities. With its rectangular shape and above ground usability, it offers...

    $373.57
    Add to Cart
  • An image of a 22 Gallon RV Holding Tank | RV99H

    36 Gallon Marine Fresh Water Tank | B383

    Introducing the 36 Gallon Marine Fresh Water Tank by One Clarion. This portable tank is specifically designed for marine use, making it perfect for boating and other water activities. With its rectangular shape and above ground usability, it offers...

    $408.72
    Add to Cart
  • An image of a 29 Gallon Marine Fresh Water Tank | B423

    36 Gallon Marine Fresh Water Tank | B340

    Introducing the 36 Gallon Marine Fresh Water Tank by One Clarion. This portable tank is perfect for marine environments and is designed to be used above ground. With its rectangular shape, it offers a spacious capacity of 36 gallons, allowing you to...

    $397.67
    Add to Cart
  • An image of a 22 Gallon Marine Fresh Water Tank | B473

    36 Gallon Marine Fresh Water Tank | B330

    Introducing the 36 Gallon Marine Fresh Water Tank by One Clarion! This portable tank is perfect for marine enthusiasts who need a reliable and convenient water storage solution. With its rectangular shape and above ground usability, this tank is designed...

    $421.77
    Add to Cart