Marine Holding Tank

Plastic Boat Tank

YatchHolding tanks are crucial to your boat’s plumbing. Our high-quality marine water tanks are the perfect choice for marine boat tanks, whether freshwater or graywater tanks, and also for RV tanks, ballast tanks, and more. Fabricated with FDA-approved virgin polyethylene plastic resin, our boat water tank is a seamless, one-piece tank that prevents water contamination and leaks. Our strong, durable marine fresh water tanks are customized to your dimensions for a perfect fit. Spin-weld fittings ensure your marine holding tank connects perfectly to your boat plumbing.

Ideal for potable water storage, all our custom holding tanks comply with FDA regulation CFR 177.1520 and Coast Guard Standards. The 3/8" thick walls completely enclose your plastic marine tank, giving it the strength it needs for extended service life. No matter the unique size or shape tank you need, we will help make sure you have the right tank fit. Talk with one of our team today!

See more details here: Marine Water Tanks (pdf)

Custom Plastic Boat Tanks

One Clarion is committed to providing you with the highest quality marine water tanks on the market! That is why our tanks are made with FDA-approved, virgin polyethylene plastic resin, making them perfect for storing potable water in boats and marine vessels such as sailboats, yachts, or deep sea fishing boats. Our one-piece marine holding tank is durable and practical, as well as seamless, so it doesn’t crack or weaken over time.

Each plastic tanks starts as a blank canvas with female NPT openings on one end, making them a great choice for any marine plumbing.  Our boat water tanks are available with spin weld fittings, making sure your tank has the perfect plumbing fit. Our cost effective and eco-friendly tanks and parts are sturdy, long lasting, and designed with your specific application in mind.

Rectangle Shaped Water Tanks

Part No. Capacity Length Width Depth
L-1 10 18 16 8
L-2 12 24 16 8
L-3 15 30 16 8
L-4 20 36 16 8
L-5 25 48 16 8
W-1 40 58 14 12
W-101 100 50 40 12
W-108 145 50 31.25 22
W-12 53 30.25 24.5 17.25
W-17 40 41 15.25 15.5
W-2 27 35 15 13
W-20 25 42 16 10

See: Full List of Rectangle Shaped Marine Tank Sizes

Bow Shaped Water Tanks

Part No. Capacity Length Width Depth
W-359 56 90 17.5 12
W-360 56 90 17.5 12
W-361 16 15 25.25 13
W-363 35 66 15.5 9.81
W-365 25 59 13.5 7.5
W-366 15 36 13.5 7.5
W-366 8 19.5 13.5 7.5
W-366 12 24 15 12

See: Full List of Bow Shaped Marine Tank Sizes

Wedge Shaped Water Tanks

Part No. Capacity Length Width Depth
W-211 72 61.75 24 13
W-215 100 78 26 14
W-224 88 73.75 24.25 12.75
W-273 70 73.75 24.25 10.75
W-274 65 69 24.25 10.75
W-281 81 70 26.75 11.75
W-303 97 73 24.75 14
W-349 82 48 40.5 11
W-350 108 76 40 10
W-353 93 59 36.5 11.375
W-358 8 19.75 17.75 8
W-374 107 76 38.5 10.125
W-375 17 24.5 22 9
W-93 150 67.5 40.5 14.25

See: Full List of Wedge Shaped Marine Tank Sizes

Why Use Roto Molding?

Our custom holding tanks are made with a roto-molding process to create a smooth, watertight product. Heat melts our virgin, polyethylene resin inside a hollow, closed mold with temperatures ranging from 260°C – 370°C. As the mold rotates, the resin coats the inside, creating tank walls with even thickness. This roto-molded tank is made to be stronger and longer lasting than other similar plastic marine tanks.

Marine Holding Tank Order Process

We are dedicated to working with you every step of the way during the process of making your custom marine water tank. Our tanks don't have pre-drilled holes, so we start with a blank canvas so we can makes holes and fittings exactly where you need them to be. Your custom boat water tank is made to fit your available space, no matter the shape or size needed.

  1. First, you will need to fill out a tank drawing with your tank specific dimensions and location.
  2. After we receive your drawings, our team will review and give you any feedback or suggestions. 
  3. We work with you until you're satisfied with the design before we processes your order.
  4. Although we encourage you to provide the most specific information available for your tank, including size and location for your tank, our team is ready to guide you through the process, making any changes you need.

*Please note, mounting straps are not included with this tank; nor is it for use with gasoline fuel storage. We have a wide range of tanks type to meet your needs. Our team will help you find the right custom tank to fit your specific needs.

Questions? We can help! Call us at 1-863-270-8118 or request a price quote.

Marine Water Tank Accessories

At One Clarion, we strive to bring you the best quality custom marine tanks to fit your specific tank needs. Our focus is making sure to meet the scope of your project, including spin mold fittings for a tight plumbing fit.  Whether your boat water tank is a unique size or shape, we will customize it to meet your requirements.

Polyethylene fittings for graywater and fresh water tanks are made with a spin welding process. Strong and durable, spin welding creates fittings that won’t leak or break. We make our fittings for your specific tank, ensuring a precise and permanent connection.


We also offer a variety of compartments, including rounded corner open ended, square corner open-ended, and square corner top and end compartments in a a wide selection of sizes.
See:List of Boat Containers Sizes



Battery boxes are available to store your marine batteries. Keep battery from tipping or accidentally shorting out, as well as protecting your battery from corrosion.
See: Battery boxes sizes


Sustainable Custom Marine Storage

Our custom marine water tank gives a sustainable solution for environmental friendly water storage. Manufactured with non-toxic material, tanks have a low carbon emission during their life cycle. Our boat tanks can withstand corrosion, are leak proof, resist UV damage, and last longer than other tanks. Reduce your carbon footprint with our flexible, cost-effective plastic marine tanks.

Questions? We can help! Call us at 1-863-270-8118 or request a price quote.

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Questions? We can help! Call us at 1-863-270-8118 or request a price quote.