The Decision in Front of You
You have a fire flow number from your sprinkler designer, a plan reviewer who wants a tank that satisfies NFPA 22, and a site plan with a finite amount of room. Now you have to pick a material — bolted corrugated steel, FRP (fiberglass) panel, or above-ground polyethylene — and commit to a capacity. That single choice drives your foundation design, your lead time, and how much maintenance the owner inherits.
Here’s how we help buyers sort it out.
Corrugated Steel vs. FRP Panel vs. Poly
Bolted Corrugated Steel Tanks With a Potable/Fire Liner
Corrugated steel tanks are the default for dedicated fire protection storage above roughly the point where poly tanks stop making sense. Panels ship on a truck and assemble on site, so you can build capacities that would be impossible to deliver as a one-piece tank. The water is held by an interior liner rather than the steel itself, and the roof options let you keep debris and sunlight out. We supply bolted steel from SBS Tanks and Pioneer Water Tanks.
Choose this when: you need large-volume dedicated fire storage, your site can accommodate a wide flat footprint and an engineered ring or slab foundation, and you want the most cost-effective dollars-per-gallon at scale.
FRP Panel Tanks
Bolted fiberglass panel tanks are also field-assembled, but the panels themselves are the water barrier. FRP is attractive where corrosion is a long-term concern, where the tank sits in a humid or chemically aggressive environment, or where the owner wants to minimize repainting and coating maintenance over decades of standby service.
Choose this when: corrosion resistance and low long-term maintenance outrank first cost, or when panelized delivery through a tight access route matters more than the lowest price per gallon.
Above-Ground Polyethylene Tanks
Above-ground poly tanks arrive complete, set on a prepared pad, and go into service quickly with no field assembly crew. For smaller fire flow demands, tank farms of multiple manifolded poly tanks, or supplemental storage feeding a fire pump alongside a well, they are the fastest and simplest option. We stock molded poly from Snyder Industries, and the Thintank vertical water tanks solve the case where the pad is long but narrow.
Choose this when: your required volume is modest, you want a short install window, or you are combining fire reserve with irrigation or process water in one straightforward vessel.
Underground fiberglass is a fourth path worth asking about if the fire marshal will accept buried storage and you cannot give up the surface area — but confirm suction lift and pump arrangement before you go that direction.
Sizing: Work From Flow and Duration, Not From a Round Number
Your fire protection engineer’s hydraulic calculation gives you two numbers: required flow in gpm and required duration in minutes for your hazard classification. Multiply them to get the effective volume the tank must deliver. Example arithmetic only: 500 gpm for 60 minutes is 30,000 gallons of usable water.
Then adjust for reality:
Usable vs. Gross Capacity. Water below the pump suction and above the maximum operating level does not count. Size the shell so the usable band meets the calc, not so the nameplate does.
Refill Credit. Some jurisdictions allow an automatic refill source to reduce stored volume. Get that in writing from the AHJ before you shrink the tank.
Suction Connection. Coordinate the outlet size, elevation, and anti-vortex arrangement with your fire pump supplier so the tank fittings match the pump’s suction requirement.
NFPA 22 Fittings. Plan for overflow, drain, level indication, access, and vent provisions as part of the order — not as an afterthought. Our level indicators and altitude valves cover the level and fill-control side of that list.
Confirm Before You Order
- Required flow (gpm) and duration (minutes) from the stamped hydraulic calculation
- Usable volume between low suction level and high water level
- AHJ position on refill credit, seismic, and any local amendments to NFPA 22
- Foundation type available: engineered slab, ring wall, or prepared pad
- Site access for panel trucks or a one-piece delivery, plus crane or forklift availability
- Suction, overflow, drain, and fill connection sizes and elevations
- Freeze protection and whether the tank will be indoors, outdoors, or partially shielded
- Roof and liner requirements if the tank also serves potable or irrigation use
Let Us Size It With You
Send us your hydraulic calculation, your site constraints, and any comments from the fire marshal. We will come back with a material recommendation, a usable-capacity check, and a CAD drawing you can drop into your submittal set. There is no charge for the sizing review.
