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1350 Gallon Low-Profile Underground Water Tank for High Groundwater Areas
The Graf Platin 1350 Gallon Underground Cistern is the ideal rainwater storage solution when deep digging isn't an option. Designed for minimal excavation and high groundwater tables, this low-profile tank is ultra-durable, easy to install, and guaranteed not to collapse when empty if installed correctly. Whether you're harvesting rainwater for landscape irrigation, toilets, or backup supply, this tank makes water storage simple, safe, and efficient, even in tight or rocky conditions.
It’s filter-ready, vehicle-load compatible, and includes a telescopic riser and childproof locking lid for a complete turnkey solution.
Features and Benefits of the Graf Platin 1350 Underground Tank
✓ No Deep Digging Required – Holds 1350 usable gallons with a shallow installation depth, saving time and avoiding excavation headaches.
✓ Stable in High Water Tables – Built to stay strong in challenging soil or wet environments. Groundwater stable up to the shoulder of the tank.
✓ Ready for Vehicle Loading (Optional) – Add a cast iron lid and heavy-duty riser to safely install the tank under driveways or parking areas.
✓ Tool-Free Setup – Telescopic riser tilts up to 5° and adjusts to grade, while the modular design simplifies placement and alignment.
✓ Large 26" Manway Access – Makes inspection and maintenance easy. Includes hose-ready lid access for simple garden use.
✓ Filter-Compatible – Add the Minimax Pro or Internal Basket Filter for clean, low-maintenance rainwater collection from roof areas up to 3,750 sq. ft.
✓ Rugged and Sustainable – Made from ultra-strong materials, easy to transport, and backed by a 15-year warranty.
Specifications for the Graf Platin 1350 Gallon Cistern
Capacity
1350 Gallons (Fully Usable)
Weight
Approx. 530 lb
Length
114 inches
Width
91 inches
Height to Tank Shoulder
37 inches
Height of Dome Collar
12.5 inches
Manway Opening
26 inches
Dome Diameter
31.5 inches
Riser Included
14-inch Telescopic Riser
Lid Type
Childproof PE Locking Lid
Groundwater Stability
Up to the tank shoulder
Vehicle Load Rated
Optional, up to 2.2 tons axle load
Installation Depth
Low-profile, shallow burial
Warranty
15 Years (Manufacturer)
Tank
400 Gallons
800 Gallons
1350 Gallons
2000 Gallons
Part No.
390000
390001
390002
390005
Weight (approx)
175 lb.
375 lb.
530 lb.
795 lb.
Length (l)
83"
96"
114"
142"
Width (w)
49"
83"
91"
89"
Height of tank shoulder (h)
28"
29"
37"
49"
Height of dome collar (hc)
12.5"
12.5"
12.5"
12.5"
Ø Manway opening (m)
26"
26"
26"
26"
Ø Tank dome (d)
31.5"
31.5"
31.5"
31.5"
Platin Tank Features
15 Year manufacturer's warranty
Minimal installation depth
Suitable for vehicle loading (when combined with cast iron lid option)
Groundwater stable to the tank shoulder
Internal pre-filtration option
Grass green telescopic riser and latching lid included
Easy to transport and install
Convenient 26" manway opening
Easy-open access in lid for garden hose connection
1350 fully-usable gallons
Ease of installation:
Minimum installation depth greatly reduces installation time and cost, while modular components and integrated filter technology make the system easy to assemble.
Ultra-high strength materials and design enable a wide variety of installation options like high groundwater tables, underneath driveways and areas where rock and other obstructions prevent deeper burial.
Telescopic riser tilts up to 5°, making it easy to match existing grade.
Warranty: 15-Year Manufacturer Guarantee when installed according to specifications.
Customers are saying
5.00 ★ (5)
Verified
Is this easy to use? I haven’t had a system like this before.
Yes, it’s designed to be simple and beginner-friendly. If you’re just using a tank or a basic bundle, it works passively, rainwater flows from your roof into the tank through a downspout diverter. There’s no need for electricity or complicated setup. If you need to add a tank to an already established rainwater system, it’s just as easy, most tanks can be connected in series or used as additional storage with a few basic fittings. We can help you choose the right components to make the expansion seamless.
How do I know what tank size I need for my home or garden?
A simple way to estimate the right tank size is by calculating how much rainwater your roof can collect. Multiply your roof’s surface area (in square feet) by your average annual rainfall (in inches), then multiply by 0.62, this gives you the total gallons you could collect in a year. For example, a 1,000 sq ft roof with 30 inches of rainfall can collect around 18,600 gallons annually. From there, we can help you choose the right tank size based on your water use and how much storage you want on hand, whether you're using it for irrigation, home use like toilets or laundry, or even potable water with proper filtration.
Can I bury this tank underground?
Yes and no, not all tanks are designed to be buried. Only tanks that are specifically rated for underground installation should be placed below ground. Always check the product specifications or reach out to us before burying any tank to ensure it’s safe and properly supported.
Is this tank safe for long-term water storage?
Absolutely. Our tanks are made from high-quality, UV-stabilized, food-grade polyethylene or reinforced materials designed for long-term rainwater storage. They resist algae growth and won’t leach chemicals into your water.
Can I collect rainwater from just one downspout?
Yes. Many basic systems start with a single downspout diverter, especially for smaller tanks. This setup is easy to install and still collects a significant amount of water, especially in areas with frequent rainfall or large roof sections.
What’s the difference between above-ground and underground tanks?
Above-ground tanks are easier to install, inspect, and move. Underground tanks save space and are often used when visual impact or limited yard space is a concern. We offer both, and we’re happy to help you decide what fits your space and needs best.
Will the tank overflow if it fills up?
No worries, each tank includes an overflow port that directs excess water safely away from the tank when it’s full. You can connect this to a drain, second tank, or garden area to make use of the overflow.
Can I connect this tank to a pump later on?
Yes. All of our tanks are compatible with add-on pumps, filters, and automation systems. You can start simple and upgrade later with no problem, just let us know your goals and we’ll help future-proof your setup.
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