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

  • 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

    This 34-gallon Ronco marine fresh water tank (B538) is built for onboard potable water storage on boats and watercraft. Measuring 26" x 22" x 20", it fits a wide range of vessel layouts and provides reliable fresh water capacity for extended trips on the...

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

    34 Gallon Marine Fresh Water Tank | B471

    This 34-gallon Ronco marine fresh water tank (B471) is built for onboard potable water storage on boats and watercraft. Measuring 34" x 31" x 16", it fits a wide range of vessel layouts and provides reliable fresh water capacity for extended trips on the...

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

    34 Gallon Marine Fresh Water Tank | B381

    This 34-gallon Ronco marine fresh water tank (B381) is built for onboard potable water storage on boats and watercraft. Measuring 34" x 26" x 9 1/2", it fits a wide range of vessel layouts and provides reliable fresh water capacity for extended trips on...

    $350.48
    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

    This 35-gallon Ronco marine fresh water tank (BOAT7W) is built for onboard potable water storage on boats and watercraft. Measuring 30" x 22" x 14", it fits a wide range of vessel layouts and provides reliable fresh water capacity for extended trips on...

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

    35 Gallon Marine Fresh Water Tank | BOAT6W

    This 35-gallon Ronco marine fresh water tank (BOAT6W) is built for onboard potable water storage on boats and watercraft. Measuring 48 3/8" x 14 3/8" x 13 1/4", it fits a wide range of vessel layouts and provides reliable fresh water capacity for...

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

    35 Gallon Marine Fresh Water Tank | BOAT38W

    This 35-gallon Ronco marine fresh water tank (BOAT38W) is built for onboard potable water storage on boats and watercraft. Measuring 45" x 18 1/2" x 11 1/4", it fits a wide range of vessel layouts and provides reliable fresh water capacity for extended...

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

    35 Gallon Marine Fresh Water Tank | BOAT1W

    This 35-gallon Ronco marine fresh water tank (BOAT1W) is built for onboard potable water storage on boats and watercraft. Measuring 32 1/8" x 19 1/2" x 15", it fits a wide range of vessel layouts and provides reliable fresh water capacity for extended...

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

    35 Gallon Marine Fresh Water Tank | B460

    This 35-gallon Ronco marine fresh water tank (B460) is built for onboard potable water storage on boats and watercraft. Measuring 36 1/2" x 37 3/8" x 11 1/4", it fits a wide range of vessel layouts and provides reliable fresh water capacity for extended...

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

    35 Gallon Marine Fresh Water Tank | B445

    This 35-gallon Ronco marine fresh water tank (B445) is built for onboard potable water storage on boats and watercraft. Measuring 44" x 16 7/8" x 23", it fits a wide range of vessel layouts and provides reliable fresh water capacity for extended trips on...

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

    35 Gallon Marine Fresh Water Tank | B431

    This 35-gallon Ronco marine fresh water tank (B431) is built for onboard potable water storage on boats and watercraft. Measuring 54" x 16" x 16", it fits a wide range of vessel layouts and provides reliable fresh water capacity for extended trips on the...

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

    35 Gallon Marine Fresh Water Tank | B371

    This 35-gallon Ronco marine fresh water tank (B371) is built for onboard potable water storage on boats and watercraft. Measuring 67" x 14" x 10", it fits a wide range of vessel layouts and provides reliable fresh water capacity for extended trips on the...

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

    35 Gallon Marine Fresh Water Tank | B203

    This 35-gallon Ronco marine fresh water tank (B203) is built for onboard potable water storage on boats and watercraft. Measuring 48" x 17" x 13 3/4", it fits a wide range of vessel layouts and provides reliable fresh water capacity for extended trips on...

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

    35 Gallon Marine Fresh Water Tank | B147

    This 35-gallon Ronco marine fresh water tank (B147) is built for onboard potable water storage on boats and watercraft. Measuring 48" x 17" x 10", it fits a wide range of vessel layouts and provides reliable fresh water capacity for extended trips on the...

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

    35 Gallon Marine Fresh Water Tank | B116

    This 35-gallon Ronco marine fresh water tank (B116) is built for onboard potable water storage on boats and watercraft. Measuring 28" x 22" x 15", it fits a wide range of vessel layouts and provides reliable fresh water capacity for extended trips on the...

    $362.53
    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

    This 36-gallon Ronco marine fresh water tank (B478) is built for onboard potable water storage on boats and watercraft. Measuring 24" x 22" x 19", it fits a wide range of vessel layouts and provides reliable fresh water capacity for extended trips on the...

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

    36 Gallon Marine Fresh Water Tank | B428

    This 36-gallon Ronco marine fresh water tank (B428) is built for onboard potable water storage on boats and watercraft. Measuring 46" x 36" x 6", it fits a wide range of vessel layouts and provides reliable fresh water capacity for extended trips on the...

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

    36 Gallon Marine Fresh Water Tank | B383

    This 36-gallon Ronco marine fresh water tank (B383) is built for onboard potable water storage on boats and watercraft. Measuring 32" x 32" x 9 1/4", it fits a wide range of vessel layouts and provides reliable fresh water capacity for extended trips on...

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

    36 Gallon Marine Fresh Water Tank | B340

    This 36-gallon Ronco marine fresh water tank (B340) is built for onboard potable water storage on boats and watercraft. Measuring 26 1/2" x 21 1/8" x 18", it fits a wide range of vessel layouts and provides reliable fresh water capacity for extended...

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

    36 Gallon Marine Fresh Water Tank | B330

    This 36-gallon Ronco marine fresh water tank (B330) is built for onboard potable water storage on boats and watercraft. Measuring 22" x 23" x 22 1/2", it fits a wide range of vessel layouts and provides reliable fresh water capacity for extended trips on...

    $421.77
    Add to Cart
  • An image of a 135 Gallon RV Fresh Water Tank | B300

    36 Gallon Marine Fresh Water Tank | B254

    This 36-gallon Ronco marine fresh water tank (B254) is built for onboard potable water storage on boats and watercraft. Measuring 28 3/8" x 17 7/8" x 17 3/4", it fits a wide range of vessel layouts and provides reliable fresh water capacity for extended...

    $373.57
    Add to Cart