Marine Water or Waste Holding Tanks - 251 to 500 Gallons
The Best Marine Water Tanks & Waste Holding Tanks for Boaters Salt. Spray. Motion. Pressure. Plumbing a boat or marine vehicle isn’t just about finding a tank that fits — it’s about choosing one that can handle life at sea. But those same elements—corrosive salt, relentless UV rays, and the constant pounding stress from waves—are absolutely brutal on your boat's equipment. This is especially true for your holding tanks. A thin, brittle, or poorly-made tank isn't just an inconvenience; it's a ticking time bomb for a catastrophic leak or a smell you can't get rid of....
That’s exactly why these tanks exist. This is our premier line of marine water and waste holding tanks, engineered to pull double duty and built to survive. Whether you need a safe, robust marine water tank for your galley or a bulletproof marine waste holding tank for black water, this is your 'buy it once' solution. Built from heavy-duty, rotationally molded, corrosion-proof polyethylene, these plastic boat tanks with sizes sizes from 3 gallons to 260 gallons are designed to fit your hull, withstand the sea, and give you one less thing to worry about. With blank tank options, pre-installed fittings, and fully customizable configurations, you’re in control of your system — down to the last thread.
Key Applications of Marine Fresh Water & Waste Holding Tanks
These tanks are the foundation of a reliable marine plumbing system, giving you the flexibility to build it right for any application.
Trust Your Water Supply
When you're miles from shore, you need a safe source. Our boat water tanks are manufactured from FDA-approved, food-grade, BPA-free resin, ensuring your water is 100% potable, safe, and taste-free.
Built for All Onboard Needs
These tanks are the perfect potable water tank for boat systems. They are built to reliably feed your galley water systems, supply deck rinse stations, and serve as durable potable water reserves on day or offshore boats.
Lock in Odors for Good
A boat holding tank for waste cannot fail. Our marine waste tanks feature a seamless, thick wall marine holding tank construction (up to 3/8-inch thick) that is impermeable to waste, permanently locking in odors and preventing leaks.
Meet All Waste Compliance Needs
Engineered as the ultimate marine black water tank, these versatile tanks are also perfect for galley or shower grey water holding. They are designed to meet the rigorous standards of boats requiring Coast Guard-compliant waste systems, giving you total peace of mind.
Why Choose Tank Depot for your Marine Fresh Water Tanks and Marine Waste Holding Tanks
When you're outfitting your vessel, you need two things: a product that can survive the sea and a partner who understands the complexity of a boat. Here’s why we are the top choice for boaters who demand reliability.
Unmatched Durability
Our tanks are rotationally molded into a single, seamless piece. This process, combined with heavy-duty polyethylene construction (up to 3/8" thick), means there are no weak points to leak, crack, or fail. They are 100% corrosion-proof, won't rust like metal, and are impervious to the stresses of salt, waste, and constant hull vibration.
Installation Flexibility
We know "one-size-fits-all" doesn't work on a boat. Many of our tanks ship "blank," allowing you to drill and place fittings to match your exact plumbing lines. Need something more? Our "Build Your Own Tank" service makes you the designer.
The Right Fit for Your Hull
Don't compromise on capacity. Our inventory is one of the largest available, with tanks from a compact 3 gallons to a massive 260 gallons.Our marine tanks are designed to maximize storage in the tight, irregular spaces of a hull.
Compliance and Peace of Mind
Sail with confidence. Our Trionic marine waste holding tanks are built to meet or exceed all U.S. Coast Guard standards, including FDA 177.1520, giving you peace of mind for inspections, pump-outs, and safe operation on the water.
Expert Support
We understand the unique challenges of marine plumbing. Our expert team can review your drawings, help you plan your system, and ensure you get the right tank and the right fittings for your specific build, the first time.
The Complete System in One Stop
A tank is just the beginning. We also stock marine and RV tank accessories, including the specific fitting kits, pump-out kits, and gauges you need to complete your installation like a pro.
Start Your System with a Marine Water & Waste Tank That’s Built for the Water — and Built to Last
From the bilge to the bow, every inch of your boat or marine vehicle serves a purpose. Your water and waste systems should be no different. At Tank Depot, we carry a full selection of marine-rated plastic holding tanks designed to make your install smoother, your system safer, and your time on the water cleaner and more reliable.
Whether you're piecing together a full marine sanitation system, upgrading an aging boat water storage tank, or starting fresh with a 50-gallon rectangular marine tank, we've got the right options to match your space, your specs, and your standards.
Not sure what size you need? Want help mapping out your fittings? Our team has helped thousands of boat owners, van lifers, and RV techs build smarter plumbing systems — and we’re here when you’re ready. Browse all options below.
