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 28 Gallon Marine Holding Tank | BOAT69W

    40 Gallon Marine Fresh Water Tank | B439

    This 40-gallon Ronco marine fresh water tank (B439) 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...

    $597.52
    Add to Cart
  • An image of a 13 Gallon Marine Holding Tank | B476

    40 Gallon Marine Fresh Water Tank | B432

    This 40-gallon Ronco marine fresh water tank (B432) is built for onboard potable water storage on boats and watercraft. Measuring 28" x 23" x 16", 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 44 Gallon Marine Fresh Water Tank | BOAT9W

    40 Gallon Marine Fresh Water Tank | B347

    This 40-gallon Ronco marine fresh water tank (B347) is built for onboard potable water storage on boats and watercraft. Measuring 34 3/4" x 26" x 11", 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 15 Gallon Marine Fresh Water Tank | B475

    40 Gallon Marine Fresh Water Tank | B339

    This 40-gallon Ronco marine fresh water tank (B339) is built for onboard potable water storage on boats and watercraft. Measuring 26 1/2" x 23" x 18", it fits a wide range of vessel layouts and provides reliable fresh water capacity for extended trips on...

    $432.83
    Add to Cart
  • An image of a 17 Gallon Marine Fresh Water Tank | B325

    40 Gallon Marine Fresh Water Tank | B309

    This 40-gallon Ronco marine fresh water tank (B309) is built for onboard potable water storage on boats and watercraft. Measuring 39" x 18" x 14", 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 10 Gallon Marine Fresh Water Tank | B389

    40 Gallon Marine Fresh Water Tank | B305

    This 40-gallon Ronco marine fresh water tank (B305) is built for onboard potable water storage on boats and watercraft. Measuring 54" x 20" 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 17 Gallon Marine Holding Tank | B325

    40 Gallon Marine Fresh Water Tank | B301

    This 40-gallon Ronco marine fresh water tank (B301) is built for onboard potable water storage on boats and watercraft. Measuring 75" x 18" x 10 1/4", it fits a wide range of vessel layouts and provides reliable fresh water capacity for extended trips on...

    $432.83
    Add to Cart
  • An image of a 25 Gallon Marine Fresh Water Tank | B408

    40 Gallon Marine Fresh Water Tank | B256

    This 40-gallon Ronco marine fresh water tank (B256) is built for onboard potable water storage on boats and watercraft. Measuring 29 7/8" x 20 7/8" x 16 5/8", it fits a wide range of vessel layouts and provides reliable fresh water capacity for extended...

    $408.72
    Add to Cart
  • An image of a 105 Gallon Marine Holding Tank | B427

    40 Gallon Marine Fresh Water Tank | B252

    This 40-gallon Ronco marine fresh water tank (B252) is built for onboard potable water storage on boats and watercraft. Measuring 26 1/2" x 21 1/4" x 18", it fits a wide range of vessel layouts and provides reliable fresh water capacity for extended...

    $408.72
    Add to Cart
  • An image of a 25 Gallon Marine Fresh Water Tank | B224

    40 Gallon Marine Fresh Water Tank | B241

    This 40-gallon Ronco marine fresh water tank (B241) is built for onboard potable water storage on boats and watercraft. Measuring 40 1/2" x 15 1/2" x 15 1/2", 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 20 Gallon Marine Holding Tank | B152

    40 Gallon Marine Fresh Water Tank | B240

    This 40-gallon Ronco marine fresh water tank (B240) is built for onboard potable water storage on boats and watercraft. Measuring 58" x 13 3/4" x 12", 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 3 Gallon RV Fresh Water Tank | RV13W

    40 Gallon Marine Fresh Water Tank | B222

    This 40-gallon Ronco marine fresh water tank (B222) is built for onboard potable water storage on boats and watercraft. Measuring 42" x 26 3/4" x 9 1/2", it fits a wide range of vessel layouts and provides reliable fresh water capacity for extended trips...

    $408.72
    Add to Cart
  • An image of a 13 Gallon Marine Fresh Water Tank | B476

    40 Gallon Marine Fresh Water Tank | B221

    This 40-gallon Ronco marine fresh water tank (B221) is built for onboard potable water storage on boats and watercraft. Measuring 23 1/2" x 23" x 18", it fits a wide range of vessel layouts and provides reliable fresh water capacity for extended trips on...

    $385.62
    Add to Cart
  • An image of a 12 Gallon RV Fresh Water Tank | RVB441

    40 Gallon Marine Fresh Water Tank | B150

    This 40-gallon Ronco marine fresh water tank (B150) is built for onboard potable water storage on boats and watercraft. Measuring 36 1/2" x 18" x 24", it fits a wide range of vessel layouts and provides reliable fresh water capacity for extended trips on...

    $421.77
    Add to Cart
  • 40 Gallon Marine Water Tank MW-500. Technical drawing of a polyethylene water tank designed for marine vessels.

    40 Gallon Marine Water Tank MW-500

    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 40 Gallon Marine Water Tank, Part# MW-500, is engineered to meet the requirements of mobile...

    MSRP: $627.65
    $596.75
    Add to Cart
  • 40 Gallon Marine Water Tank MW-484. Technical drawing of a polyethylene water tank designed for marine vessels.

    40 Gallon Marine Water Tank MW-484

    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 40 Gallon Marine Water Tank, Part# MW-484, is engineered to meet the requirements of mobile...

    MSRP: $392.02
    $372.73
    Add to Cart
  • 40 Gallon Marine Water Tank MW-443. Technical drawing of a polyethylene water tank designed for marine vessels.

    40 Gallon Marine Water Tank MW-443

    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 40 Gallon Marine Water Tank, Part# MW-443, is engineered to meet the requirements of mobile...

    MSRP: $392.02
    $372.73
    Add to Cart
  • 40 Gallon Marine Water Tank MW-296. Technical drawing of a polyethylene water tank designed for marine vessels.

    40 Gallon Marine Water Tank MW-296

    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 40 Gallon Marine Water Tank, Part# MW-296, is engineered to meet the requirements of mobile...

    MSRP: $380.23
    $361.52
    Add to Cart
  • 40 Gallon Marine Water Tank MW-295. Technical drawing of a polyethylene water tank designed for marine vessels.

    40 Gallon Marine Water Tank MW-295

    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 40 Gallon Marine Water Tank, Part# MW-295, is engineered to meet the requirements of mobile...

    MSRP: $461.34
    $438.64
    Add to Cart
  • 40 Gallon Marine Water Tank MW-294. Technical drawing of a polyethylene water tank designed for marine vessels.

    40 Gallon Marine Water Tank MW-294

    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 40 Gallon Marine Water Tank, Part# MW-294, is engineered to meet the requirements of mobile...

    MSRP: $383.14
    $364.28
    Add to Cart
  • 40 Gallon Marine Water Tank MW-293. Technical drawing of a polyethylene water tank designed for marine vessels.

    40 Gallon Marine Water Tank MW-293

    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 40 Gallon Marine Water Tank, Part# MW-293, is engineered to meet the requirements of mobile...

    MSRP: $324.58
    $308.61
    Add to Cart
  • 40 Gallon Marine Water Tank MW-291. Technical drawing of a polyethylene water tank designed for marine vessels.

    40 Gallon Marine Water Tank MW-291

    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 40 Gallon Marine Water Tank, Part# MW-291, is engineered to meet the requirements of mobile...

    MSRP: $362.25
    $344.42
    Add to Cart
  • 40 Gallon Marine Water Tank MW-284. Technical drawing of a polyethylene water tank designed for marine vessels.

    40 Gallon Marine Water Tank MW-284

    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 40 Gallon Marine Water Tank, Part# MW-284, is engineered to meet the requirements of mobile...

    MSRP: $371.26
    $352.98
    Add to Cart
  • 40 Gallon Marine Water Tank MW-270. Technical drawing of a polyethylene water tank designed for marine vessels.

    40 Gallon Marine Water Tank MW-270

    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 40 Gallon Marine Water Tank, Part# MW-270, is engineered to meet the requirements of mobile...

    MSRP: $461.78
    $439.05
    Add to Cart
  • 40 Gallon Marine Water Tank MW-256. Technical drawing of a polyethylene water tank designed for marine vessels.

    40 Gallon Marine Water Tank MW-256

    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 40 Gallon Marine Water Tank, Part# MW-256, is engineered to meet the requirements of mobile...

    MSRP: $353.07
    $335.69
    Add to Cart
  • 40 Gallon Marine Water Tank MW-248. Technical drawing of a polyethylene water tank designed for marine vessels.

    40 Gallon Marine Water Tank MW-248

    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 40 Gallon Marine Water Tank, Part# MW-248, is engineered to meet the requirements of mobile...

    MSRP: $344.05
    $327.11
    Add to Cart
  • 40 Gallon Marine Water Tank MW-231. Technical drawing of a polyethylene water tank designed for marine vessels.

    40 Gallon Marine Water Tank MW-231

    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 40 Gallon Marine Water Tank, Part# MW-231, is engineered to meet the requirements of mobile...

    MSRP: $408.45
    $388.34
    Add to Cart