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 36 Gallon Marine Holding Tank | B428

    36 Gallon Marine Fresh Water Tank | B158

    This 36-gallon Ronco marine fresh water tank (B158) is built for onboard potable water storage on boats and watercraft. Measuring 30 1/2" x 21 1/2" x 13 3/4", it fits a wide range of vessel layouts and provides reliable fresh water capacity for extended...

    $373.57
    Add to Cart
  • 36 Gallon Marine Water Tank MW-531. Technical drawing of a polyethylene water tank designed for marine vessels.

    36 Gallon Marine Water Tank MW-531

    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 36 Gallon Marine Water Tank, Part# MW-531, is engineered to meet the requirements of mobile...

    MSRP: $503.25
    $478.48
    Add to Cart
  • 36 Gallon Marine Water Tank MW-503. Technical drawing of a polyethylene water tank designed for marine vessels.

    36 Gallon Marine Water Tank MW-503

    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 36 Gallon Marine Water Tank, Part# MW-503, is engineered to meet the requirements of mobile...

    MSRP: $334.42
    $317.96
    Add to Cart
  • 36 Gallon Marine Water Tank MW-469. Technical drawing of a polyethylene water tank designed for marine vessels.

    36 Gallon Marine Water Tank MW-469

    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 36 Gallon Marine Water Tank, Part# MW-469, is engineered to meet the requirements of mobile...

    MSRP: $398.69
    $379.07
    Add to Cart
  • 36 Gallon Marine Water Tank MW-3. Technical drawing of a polyethylene water tank designed for marine vessels.

    36 Gallon Marine Water Tank MW-3

    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 36 Gallon Marine Water Tank, Part# MW-3, is engineered to meet the requirements of mobile...

    MSRP: $377.57
    $358.99
    Add to Cart
  • An image of a 30 Gallon Marine Fresh Water Tank | B502

    37 Gallon Marine Fresh Water Tank | BOAT17W

    This 37-gallon Ronco marine fresh water tank (BOAT17W) is built for onboard potable water storage on boats and watercraft. Measuring 40 1/2" x 24" x 10", it fits a wide range of vessel layouts and provides reliable fresh water capacity for extended trips...

    $397.67
    Add to Cart
  • An image of a 27 Gallon Marine Holding Tank | B342

    37 Gallon Marine Fresh Water Tank | B489

    This 37-gallon Ronco marine fresh water tank (B489) is built for onboard potable water storage on boats and watercraft. Measuring 45 7/8" x 18 1/2" x 13 7/8", 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 9 Gallon Marine Fresh Water Tank | B288

    37 Gallon Marine Fresh Water Tank | B372

    This 37-gallon Ronco marine fresh water tank (B372) is built for onboard potable water storage on boats and watercraft. Measuring 42 1/2" x 17" x 12 3/4", it fits a wide range of vessel layouts and provides reliable fresh water capacity for extended...

    $397.67
    Add to Cart
  • 37 Gallon Marine Water Tank MW-478. Technical drawing of a polyethylene water tank designed for marine vessels.

    37 Gallon Marine Water Tank MW-478

    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 37 Gallon Marine Water Tank, Part# MW-478, is engineered to meet the requirements of mobile...

    MSRP: $462.51
    $439.74
    Add to Cart
  • 37 Gallon Marine Water Tank MW-452. Technical drawing of a polyethylene water tank designed for marine vessels.

    37 Gallon Marine Water Tank MW-452

    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 37 Gallon Marine Water Tank, Part# MW-452, is engineered to meet the requirements of mobile...

    MSRP: $285.80
    $271.73
    Add to Cart
  • 37 Gallon Marine Water Tank MW-259. Technical drawing of a polyethylene water tank designed for marine vessels.

    37 Gallon Marine Water Tank MW-259

    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 37 Gallon Marine Water Tank, Part# MW-259, is engineered to meet the requirements of mobile...

    MSRP: $300.45
    $285.66
    Add to Cart
  • An image of a 23 Gallon Marine Fresh Water Tank | B429

    38 Gallon Marine Fresh Water Tank | B403

    This 38-gallon Ronco marine fresh water tank (B403) is built for onboard potable water storage on boats and watercraft. Measuring 48" x 21 1/2" x 18", 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 70 Gallon Marine Fresh Water Tank | B401

    38 Gallon Marine Fresh Water Tank | B362

    This 38-gallon Ronco marine fresh water tank (B362) is built for onboard potable water storage on boats and watercraft. Measuring 32 3/4" x 20 1/4" x 20 3/4", it fits a wide range of vessel layouts and provides reliable fresh water capacity for extended...

    $421.77
    Add to Cart
  • An image of a 12 Gallon RV Holding Tank | RV41H

    38 Gallon Marine Fresh Water Tank | B346

    This 38-gallon Ronco marine fresh water tank (B346) is built for onboard potable water storage on boats and watercraft. Measuring 37" x 28" x 9", it fits a wide range of vessel layouts and provides reliable fresh water capacity for extended trips on the...

    $408.72
    Add to Cart
  • An image of a 100 Gallon Marine Fresh Water Tank | B249

    38 Gallon Marine Fresh Water Tank | B311

    This 38-gallon Ronco marine fresh water tank (B311) is built for onboard potable water storage on boats and watercraft. Measuring 37 3/4" x 16" x 16", it fits a wide range of vessel layouts and provides reliable fresh water capacity for extended trips on...

    $431.82
    Add to Cart
  • 38 Gallon Marine Water Tank MW-516. Technical drawing of a polyethylene water tank designed for marine vessels.

    38 Gallon Marine Water Tank MW-516

    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 38 Gallon Marine Water Tank, Part# MW-516, is engineered to meet the requirements of mobile...

    MSRP: $605.71
    $575.89
    Add to Cart
  • 38 Gallon Marine Water Tank MW-453. Technical drawing of a polyethylene water tank designed for marine vessels.

    38 Gallon Marine Water Tank MW-453

    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 38 Gallon Marine Water Tank, Part# MW-453, is engineered to meet the requirements of mobile...

    MSRP: $439.77
    $418.12
    Add to Cart
  • 38 Gallon Marine Water Tank MW-406. Technical drawing of a polyethylene water tank designed for marine vessels.

    38 Gallon Marine Water Tank MW-406

    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 38 Gallon Marine Water Tank, Part# MW-406, is engineered to meet the requirements of mobile...

    MSRP: $522.62
    $496.89
    Add to Cart
  • 38 Gallon Marine Water Tank MW-255. Technical drawing of a polyethylene water tank designed for marine vessels.

    38 Gallon Marine Water Tank MW-255

    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 38 Gallon Marine Water Tank, Part# MW-255, is engineered to meet the requirements of mobile...

    MSRP: $388.34
    $369.22
    Add to Cart
  • 38 Gallon Marine Water Tank MW-240. Technical drawing of a polyethylene water tank designed for marine vessels.

    38 Gallon Marine Water Tank MW-240

    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 38 Gallon Marine Water Tank, Part# MW-240, is engineered to meet the requirements of mobile...

    MSRP: $388.99
    $369.84
    Add to Cart
  • 38 Gallon Marine Water Tank MW-227. Technical drawing of a polyethylene water tank designed for marine vessels.

    38 Gallon Marine Water Tank MW-227

    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 38 Gallon Marine Water Tank, Part# MW-227, is engineered to meet the requirements of mobile...

    MSRP: $487.74
    $463.73
    Add to Cart
  • 38 Gallon Marine Water Tank MW-202. Technical drawing of a polyethylene water tank designed for marine vessels.

    38 Gallon Marine Water Tank MW-202

    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 38 Gallon Marine Water Tank, Part# MW-202, is engineered to meet the requirements of mobile...

    MSRP: $341.54
    $324.73
    Add to Cart
  • An image of a 93 Gallon Marine Holding Tank | BOAT66W

    39 Gallon Marine Fresh Water Tank | B469

    This 39-gallon Ronco marine fresh water tank (B469) is built for onboard potable water storage on boats and watercraft. Measuring 33 1/4" x 25 3/4" x 17 3/8", it fits a wide range of vessel layouts and provides reliable fresh water capacity for extended...

    $480.02
    Add to Cart
  • 39 Gallon Marine Water Tank MW-416. Technical drawing of a polyethylene water tank designed for marine vessels.

    39 Gallon Marine Water Tank MW-416

    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 39 Gallon Marine Water Tank, Part# MW-416, is engineered to meet the requirements of mobile...

    MSRP: $491.97
    $467.74
    Add to Cart
  • 39 Gallon Marine Water Tank MW-258. Technical drawing of a polyethylene water tank designed for marine vessels.

    39 Gallon Marine Water Tank MW-258

    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 39 Gallon Marine Water Tank, Part# MW-258, is engineered to meet the requirements of mobile...

    MSRP: $392.02
    $372.73
    Add to Cart
  • 39 Gallon Marine Water Tank MW-257. Technical drawing of a polyethylene water tank designed for marine vessels.

    39 Gallon Marine Water Tank MW-257

    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 39 Gallon Marine Water Tank, Part# MW-257, is engineered to meet the requirements of mobile...

    MSRP: $494.72
    $470.37
    Add to Cart
  • An image of a 35 Gallon Marine Fresh Water Tank | B460

    40 Gallon Marine Fresh Water Tank | B456

    This 40-gallon Ronco marine fresh water tank (B456) is built for onboard potable water storage on boats and watercraft. Measuring 37 3/4" x 22 1/4" x 12 5/8", it fits a wide range of vessel layouts and provides reliable fresh water capacity for extended...

    $431.82
    Add to Cart