500 Gallon Doorway Water Tank - White (31" x 70"): Complete Buyer's Guide
500-gallon white doorway tank built for tight-access indoor liquid storage. Manufactured by Norwesco from virgin linear polyethylene (HDPE) rated to handle liquids up to 12.5 pounds per gallon. FDA approved for contact with potable water, ensuring safe storage for drinking water and food-grade liquids.
Specifications at a Glance
Every figure below is pulled straight from the live product record for this exact tank — the same data on the product page, so what you read here and what you buy never disagree.
Standards & Materials
- ASTM D1998 — Standard Specification for Polyethylene Upright Storage Tanks. Governs wall-thickness and hydrostatic design for vertical rotomolded poly tanks of this class.
- FDA 21 CFR 177.1520 — Olefin polymers. The food-contact regulation the FDA-grade resin in this tank is compounded to meet.
- Specific gravity rating 1.5 — the tank is engineered for liquids up to 1.5× the density of water (water is about 8.34 lb/gal). Confirm your fluid’s SG before storage.
Product Overview
The 500 Gallon Doorway Water Tank solves a problem that defeats ordinary tanks: getting real storage capacity into a finished building. At just 31 inches wide it slips through a standard 32-inch doorway, so you can roll it into a basement, a utility room, a barn stall, or an interior mechanical space that a round 500-gallon tank could never enter. The narrow, upright rectangular form is engineered specifically for that move.
Norwesco rotationally molds it in one seamless piece of virgin linear polyethylene, rated to 1.5 specific gravity, which means it holds water and water-based liquids up to 12.5 pounds per gallon — a broader rating than a typical water-only tank. The translucent natural-white wall lets you read the level at a glance and reflects light to keep the contents cooler, with molded-in UV stabilizers and a 120 F / 48 C service ceiling for the occasions it lives outdoors.
The tank measures 74 inches long, 31 inches wide, and 70 inches tall, weighs 194 pounds empty, and reaches about 6,449 pounds full at 1.5 SG. A factory 1.25-inch NPT outlet feeds your line, and the 16-inch lid opens for filling, venting, and access. Norwesco backs it with a 3-year warranty against manufacturing defects, and we inspect each unit before it ships.
Technical Drawing
Official Norwesco technical drawing — 500 Gallon Doorway Water Tank - White (31" x 70")
Key Features and Specifications
- 500-gallon capacity — sized for tight-access indoor liquid storage
- Constructed from virgin linear polyethylene (HDPE) with 1.5 specific gravity rating — handles liquids up to 12.5 lbs/gal
- 74" long x 31" wide x 70" tall
- 194 lbs empty, approximately 6,449 lbs when full at rated specific gravity
- 1.25 NPT outlet fitting — factory installed and leak-tested
- 16" lid opening for fill, venting, and interior access
- FDA approved for potable water and food-grade liquid contact
- 3 Year Warranty from Norwesco against manufacturing defects
- Translucent white walls allow visual level monitoring without opening the tank and reflect sunlight to keep contents cooler
- Rated for continuous service up to 120 F / 48 C
- Seamless one-piece rotational molding — no seams, no welds, no leak points
- Manufactured by Norwesco — a leading name in rotomolded polyethylene tanks
- Place on a firm, level surface free of rocks or sharp objects that could damage the tank bottom. Ensure adequate ventilation if stored chemicals produce vapors
- Ships via LTL freight on a pallet — residential delivery with lift gate available
Installation and Setup Guide
Everything distinctive about installing this tank flows from its 31-inch width. The whole reason to buy a doorway tank is to put storage where storage normally cannot go, so the installation begins not at the pad but at the path you will take to reach it.
Plan the Route In
Before delivery, walk the route from the truck to the final spot and measure every pinch point: door openings, hallway turns, stair widths, and ceiling height for the 70-inch tank. The tank clears a standard doorway with its 31-inch width, but a tight 90-degree turn in a narrow hall can still stop it. Empty it weighs 194 pounds, so two people can carry or dolly it through, but only if the path is clear.
Setting It Indoors
Full, the tank presses down at about 6,449 pounds over a small rectangular footprint, so confirm the floor can carry that load — a concrete slab handles it easily, but a wood-framed upper floor may not. Set it on a firm, level surface swept clean of debris, and leave room at the lid and the outlet for filling and service. The flat-sided form lets it sit flush against a wall, which is part of its space-saving appeal.
Plumbing and Venting
Connect the 1.25-inch outlet with a flexible first foot so the wall can move with temperature, and add a shutoff valve for isolation. Fit a screened vent in the 16-inch lid so air replaces liquid as you draw down; even indoors a closed tank will dent under a hard pump if it cannot breathe. The screen keeps the stored water clean.
Maintenance and Long-Term Care
As a water tank, this unit takes genuine potable maintenance, and its indoor home actually makes upkeep easier — no weather, no sun, and a tank you can reach without going outside.
Routine Checks
- Wall and fittings: Backlight the translucent white wall now and then to read the level and spot any bulge, and hand-snug the 1.25-inch outlet if it has loosened.
- Floor and footprint: Confirm the tank still sits level and the floor beneath shows no sign of distress under the load.
- Lid and vent: Make sure the 16-inch lid seats fully and the vent screen is clear so nothing enters the water.
Annual Sanitizing
For drinking-water service, drain and flush the tank yearly to clear sediment, then disinfect before refilling using the potable standard — a quarter cup of unscented household bleach per fifteen gallons, held in the filled tank for two hours, then drained and rinsed until the chlorine smell is gone. If you store a water-based solution instead, follow that product's cleaning guidance before switching contents.
Indoor Advantage
Kept inside, the translucent white wall sees no UV and the molded-in stabilizers go essentially untaxed, so the resin ages very slowly. There is no freeze risk in a heated space, and the cooler indoor temperatures keep stored water fresher longer than an outdoor tank in summer sun.
Alternatives and Comparisons
The defining specification of this tank is its 31-inch width, and that is the lens for every comparison.
Doorway tank vs. standard round tank: A conventional 500-gallon tank is wider than most doorways and simply cannot be brought inside a finished building — it has to live outdoors or be installed before walls go up. This doorway tank trades the round profile for a narrow rectangular one so it fits through the door after the building exists, which is the entire point. The trade-off is footprint efficiency: a round tank packs more gallons into less floor area, so if your storage is going outdoors anyway, the round tank is the better value. Indoors, the doorway form is often the only option that works.
Other 500-Gallon Options
Frequently Asked Questions
How long will the 500 Gallon Doorway Water Tank - White (31" x 70") last?
Indoors, where most doorway tanks live, this tank can well exceed the typical 15-to-20-year span because it is shielded from sun and weather entirely. The molded-in UV stabilizers see little load behind walls, and the seamless rotomolded body has no joint to fail. Used within its 1.5 SG and 120 F ratings and kept clean, it is a very long-lived tank.
What chemicals can I store in this tank?
It is a water tank rated to 1.5 specific gravity, so its primary role is potable and general water storage, and it can also hold water-based liquids up to 12.5 pounds per gallon within that density. Fuels, solvents, and flammables are out of bounds. For anything beyond water, confirm the specific liquid against a polyethylene compatibility chart before filling.
What kind of foundation does a 500-gallon tank need?
A full 500-gallon doorway tank weighs about 6,449 pounds over a compact rectangular footprint. Indoors, a concrete slab carries that without issue; on a framed floor, verify the structure can bear the concentrated load. The surface must be flat and clear of debris so the tank bottom is evenly supported.
Does this tank come with a warranty?
Yes. Norwesco backs it with a 3-year warranty against manufacturing defects in materials and workmanship under normal use — molded-in faults such as pinholes, cracks, and fitting defects. It does not cover damage from overloading beyond the rated specific gravity, an unsound floor, incompatible liquids, or impact. Keep your receipt and a photo of the install.
Can I install this tank underground?
No. This is an above-ground tank and its walls are not engineered to resist soil pressure; burying it would risk collapse and void the warranty. For below-grade water storage, our underground cisterns are reinforced specifically for that load.
Buying Considerations
Three things decide whether this 500-gallon doorway tank works for you. First and most important, the access route: measure every doorway, turn, and stair between the truck and the final position, since the 31-inch width is its whole purpose. Second, the floor, which must carry roughly 6,449 pounds when the tank is full — straightforward on a slab, worth checking on a framed floor. Third, your fittings, matched to the 1.25-inch outlet. Listed at $1,295.94 before freight, with delivery quoted to your ZIP.
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