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 38 Gallon Marine Holding Tank | B311

    20 Gallon Marine Fresh Water Tank | B193

    This 20-gallon Ronco marine fresh water tank (B193) is built for onboard potable water storage on boats and watercraft. Measuring 51" x 18" x 13", it fits a wide range of vessel layouts and provides reliable fresh water capacity for extended trips on the...

    $327.38
    Add to Cart
  • An image of a 35 Gallon Marine Fresh Water Tank | BOAT6W

    20 Gallon Marine Fresh Water Tank | B187

    This 20-gallon Ronco marine fresh water tank (B187) is built for onboard potable water storage on boats and watercraft. Measuring 31" x 26" x 13", it fits a wide range of vessel layouts and provides reliable fresh water capacity for extended trips on the...

    $327.38
    Add to Cart
  • An image of a 22 Gallon PP Ronco White Rectangular Open Top Tank | 24X8X30PP

    20 Gallon Marine Fresh Water Tank | B185

    This 20-gallon Ronco marine fresh water tank (B185) is built for onboard potable water storage on boats and watercraft. Measuring 57" x 11" x 11", it fits a wide range of vessel layouts and provides reliable fresh water capacity for extended trips on the...

    $339.43
    Add to Cart
  • An image of a 100 Gallon Marine Holding Tank | B313

    20 Gallon Marine Fresh Water Tank | B181

    This 20-gallon Ronco marine fresh water tank (B181) is built for onboard potable water storage on boats and watercraft. Measuring 30" x 18" x 10 1/2", it fits a wide range of vessel layouts and provides reliable fresh water capacity for extended trips on...

    $268.13
    Add to Cart
  • An image of a 34 Gallon PE Ronco White Rectangular Open Top Tank | 30X24X12PE

    20 Gallon Marine Fresh Water Tank | B165

    This 20-gallon Ronco marine fresh water tank (B165) is built for onboard potable water storage on boats and watercraft. Measuring 28 1/2" x 11 1/2" x 18", it fits a wide range of vessel layouts and provides reliable fresh water capacity for extended...

    $327.38
    Add to Cart
  • An image of a 32 Gallon Marine Fresh Water Tank | B127

    20 Gallon Marine Fresh Water Tank | B164

    This 20-gallon Ronco marine fresh water tank (B164) is built for onboard potable water storage on boats and watercraft. Measuring 44" x 13" x 12", it fits a wide range of vessel layouts and provides reliable fresh water capacity for extended trips on the...

    $327.38
    Add to Cart
  • An image of a 16 Gallon Marine Holding Tank | B364

    20 Gallon Marine Fresh Water Tank | B152

    This 20-gallon Ronco marine fresh water tank (B152) is built for onboard potable water storage on boats and watercraft. Measuring 48" x 19 1/2" x 12 3/4", it fits a wide range of vessel layouts and provides reliable fresh water capacity for extended...

    $327.38
    Add to Cart
  • An image of a 18 Gallon Marine Fresh Water Tank | B294

    20 Gallon Marine Fresh Water Tank | B146

    This 20-gallon Ronco marine fresh water tank (B146) is built for onboard potable water storage on boats and watercraft. Measuring 36" x 17 1/2" x 9 3/4", it fits a wide range of vessel layouts and provides reliable fresh water capacity for extended trips...

    $304.28
    Add to Cart
  • An image of a 20 Gallon Marine Holding Tank | B137

    20 Gallon Marine Fresh Water Tank | B137

    This 20-gallon Ronco marine fresh water tank (B137) is built for onboard potable water storage on boats and watercraft. Measuring 29 1/2" x 13 1/4" x 14", it fits a wide range of vessel layouts and provides reliable fresh water capacity for extended...

    $281.18
    Add to Cart
  • An image of a 32 Gallon Marine Holding Tank | B127

    20 Gallon Marine Fresh Water Tank | B103

    This 20-gallon Ronco marine fresh water tank (B103) is built for onboard potable water storage on boats and watercraft. Measuring 34" x 13" x 14", it fits a wide range of vessel layouts and provides reliable fresh water capacity for extended trips on the...

    $281.18
    Add to Cart
  • 20 Gallon Marine Water Tank MW-95. Technical drawing of a polyethylene water tank designed for marine vessels.

    20 Gallon Marine Water Tank MW-95

    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 20 Gallon Marine Water Tank, Part# MW-95, is engineered to meet the requirements of mobile...

    MSRP: $252.57
    $240.13
    Add to Cart
  • 20 Gallon Marine Water Tank MW-81. Technical drawing of a polyethylene water tank designed for marine vessels.

    20 Gallon Marine Water Tank MW-81

    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 20 Gallon Marine Water Tank, Part# MW-81, is engineered to meet the requirements of mobile...

    MSRP: $266.50
    $253.38
    Add to Cart
  • 20 Gallon Marine Water Tank MW-80. Technical drawing of a polyethylene water tank designed for marine vessels.

    20 Gallon Marine Water Tank MW-80

    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 20 Gallon Marine Water Tank, Part# MW-80, is engineered to meet the requirements of mobile...

    MSRP: $230.11
    $218.78
    Add to Cart
  • 20 Gallon Marine Water Tank MW-535. Technical drawing of a polyethylene water tank designed for marine vessels.

    20 Gallon Marine Water Tank MW-535

    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 20 Gallon Marine Water Tank, Part# MW-535, is engineered to meet the requirements of mobile...

    MSRP: $374.25
    $355.82
    Add to Cart
  • 20 Gallon Marine Water Tank MW-523. Technical drawing of a polyethylene water tank designed for marine vessels.

    20 Gallon Marine Water Tank MW-523

    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 20 Gallon Marine Water Tank, Part# MW-523, is engineered to meet the requirements of mobile...

    MSRP: $309.83
    $294.58
    Add to Cart
  • 20 Gallon Marine Water Tank MW-51. Technical drawing of a polyethylene water tank designed for marine vessels.

    20 Gallon Marine Water Tank MW-51

    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 20 Gallon Marine Water Tank, Part# MW-51, is engineered to meet the requirements of mobile...

    MSRP: $215.84
    $205.21
    Add to Cart
  • 20 Gallon Marine Water Tank MW-455. Technical drawing of a polyethylene water tank designed for marine vessels.

    20 Gallon Marine Water Tank MW-455

    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 20 Gallon Marine Water Tank, Part# MW-455, is engineered to meet the requirements of mobile...

    MSRP: $236.13
    $224.51
    Add to Cart
  • 20 Gallon Marine Water Tank MW-423. Technical drawing of a polyethylene water tank designed for marine vessels.

    20 Gallon Marine Water Tank MW-423

    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 20 Gallon Marine Water Tank, Part# MW-423, is engineered to meet the requirements of mobile...

    MSRP: $243.27
    $231.30
    Add to Cart
  • 20 Gallon Marine Water Tank MW-368. Technical drawing of a polyethylene water tank designed for marine vessels.

    20 Gallon Marine Water Tank MW-368

    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 20 Gallon Marine Water Tank, Part# MW-368, is engineered to meet the requirements of mobile...

    MSRP: $226.39
    $215.25
    Add to Cart
  • 20 Gallon Marine Water Tank ML-4. Technical drawing of a polyethylene water tank designed for marine vessels.

    20 Gallon Marine Water Tank ML-4

    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 20 Gallon Marine Water Tank, Part# ML-4, is engineered to meet the requirements of mobile...

    MSRP: $269.18
    $255.93
    Add to Cart
  • An image of a 80 Gallon Marine Fresh Water Tank | B299

    21 Gallon Marine Fresh Water Tank | B503

    This 21-gallon Ronco marine fresh water tank (B503) is built for onboard potable water storage on boats and watercraft. Measuring 16" x 17 3/4" x 24", it fits a wide range of vessel layouts and provides reliable fresh water capacity for extended trips on...

    $397.67
    Add to Cart
  • An image of a 90 Gallon Marine Fresh Water Tank | B314

    21 Gallon Marine Fresh Water Tank | B490

    This 21-gallon Ronco marine fresh water tank (B490) is built for onboard potable water storage on boats and watercraft. Measuring 30" x 18" x 11 7/8", 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 5 Gallon Marine Holding Tank | B377

    21 Gallon Marine Fresh Water Tank | B396

    This 21-gallon Ronco marine fresh water tank (B396) is built for onboard potable water storage on boats and watercraft. Measuring 37 3/4" x 20" x 10 3/4", 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 15 Gallon Marine Holding Tank | B264

    21 Gallon Marine Fresh Water Tank | B355

    This 21-gallon Ronco marine fresh water tank (B355) is built for onboard potable water storage on boats and watercraft. Measuring 53 1/2" x 16 3/4" x 6", it fits a wide range of vessel layouts and provides reliable fresh water capacity for extended trips...

    $326.38
    Add to Cart
  • An image of a 14 Gallon Marine Fresh Water Tank | B265

    21 Gallon Marine Fresh Water Tank | B281

    This 21-gallon Ronco marine fresh water tank (B281) is built for onboard potable water storage on boats and watercraft. Measuring 9 7/8" x 16 7/8" x 16 3/8", it fits a wide range of vessel layouts and provides reliable fresh water capacity for extended...

    $315.32
    Add to Cart
  • An image of a 80 Gallon Marine Holding Tank | B299

    21 Gallon Marine Fresh Water Tank | B219

    This 21-gallon Ronco marine fresh water tank (B219) is built for onboard potable water storage on boats and watercraft. Measuring 59 3/4" x 17 3/4" x 7 1/4", 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 52 Gallon Marine Fresh Water Tank | B295

    21 Gallon Marine Fresh Water Tank | B151

    This 21-gallon Ronco marine fresh water tank (B151) is built for onboard potable water storage on boats and watercraft. Measuring 41 1/2" x 17 1/2" x 11", it fits a wide range of vessel layouts and provides reliable fresh water capacity for extended...

    $327.38
    Add to Cart
  • An image of a 21 Gallon Marine Holding Tank | B151

    21 Gallon Marine Fresh Water Tank | B148

    This 21-gallon Ronco marine fresh water tank (B148) is built for onboard potable water storage on boats and watercraft. Measuring 27 1/2" x 13 3/4" x 19 1/4", it fits a wide range of vessel layouts and provides reliable fresh water capacity for extended...

    $304.28
    Add to Cart
  • An image of a 30 Gallon Marine Holding Tank | B140

    21 Gallon Marine Fresh Water Tank | B110

    This 21-gallon Ronco marine fresh water tank (B110) is built for onboard potable water storage on boats and watercraft. Measuring 28" x 13 1/4" x 20", it fits a wide range of vessel layouts and provides reliable fresh water capacity for extended trips on...

    $304.28
    Add to Cart