500 Gallon Doorway Water Tank (31" x 68"): Complete Buyer's Guide
500 Gallon Doorway Water Tank (31" x 68") from Norwesco.
Technical Drawing
Official Norwesco technical drawing — 500 Gallon Doorway Water Tank (31" x 68")
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.
Installation and Setup Guide
The 500-gallon doorway tank is the largest of the through-the-door reserves, and at 31 inches across it is the one to measure carefully: that width clears most standard 32-inch and wider openings but leaves little margin on a tight 30-inch door, so checking the access route is not optional here, it is the first task. Walk the full path, measure the narrowest door and corner, and confirm a 31-inch body will pass before the tank ever arrives.
Site Preparation
Five hundred gallons is the most water of any doorway tank in this group — well over four thousand pounds full — so the indoor surface it lands on must be genuinely rated for that load. A ground-floor or basement slab is the safe choice; a framed floor needs an engineer's blessing before you fill. Set the 68-inch body on a flat, level base so the load spreads evenly across the bottom rather than concentrating on a leaning edge.
Placement and Connections
Indoor installs reward tidy plumbing, and at 500 gallons the discharge carries real flow. Take it off the lowest fitting, use a flexible connector on the first run so the filling tank can move slightly without loading the bulkhead, and route the line directly to what it feeds. Hand-tighten the threads a quarter turn past snug; in the close quarters of an indoor job, a wrench is a temptation that ends in a cracked fitting.
Venting
An enclosed 500-gallon tank moves a lot of air as it cycles, so venting is critical. Keep the lid vent open and screened so the shell pulls air in on draw-down — the largest air exchange of any doorway tank here — and pushes it out on fill. A blocked vent on a tank this size will deform the wall fast under a hard pump-out, even indoors, so keep that screen clear.
Maintenance and Long-Term Care
A 500-gallon doorway tank gives you a substantial indoor reserve with the low-maintenance benefits of living out of the weather. The routine is about keeping that larger volume fresh and confirming the heavier load still has sound support beneath it.
Quarterly Inspection Checklist
- Wall sweep: Look over the 68-inch body for any bulge or weeping; the larger the doorway tank, the more its lower wall carries, so watch that region.
- Outlet check: Hand-snug the discharge fitting if it has loosened, keeping wrenches off the poly threads.
- Support audit: Verify the indoor floor or slab still carries the full four-thousand-plus-pound load with no sagging or cracking.
- Vent clearance: Confirm the screened vent is open and clear so the largest doorway tank can breathe through every cycle.
Cleaning
Drain all 500 gallons through the bottom outlet annually, rinse the interior, then sanitize on the refill with about a quarter cup of unscented bleach per fifteen gallons, two hours of contact, then flush until the chlorine smell clears. The larger volume means more water sitting between turnovers, so for an indoor potable supply this annual reset is the habit that keeps it drinkable.
UV and Weather Protection
Kept indoors, this 500-gallon tank is shielded from the UV that ages outdoor tanks, which lets it run for many years with little wear. The exception is a sun-drenched window or greenhouse; in a normal indoor space, sunlight plays no role in its service life.
Alternatives and Comparisons
At 500 gallons, this is the high-capacity end of the doorway line, holding twice the 250-gallon model while still clearing standard openings. If you need more and can store outdoors, the wider yard tanks hold far greater volumes; if access is the real constraint, this tank is the most water you can reasonably move through a door. Choose by your narrowest opening first.
Doorway/Slimline vs. Standard: Doorway tanks sacrifice some structural efficiency for a narrow profile that fits through standard 32-inch doors. The rectangular footprint is less structurally efficient than a cylinder, so wall thickness is heavier for the same capacity. If you don't need to move the tank through a doorway, a standard vertical tank gives you more capacity per pound of material.
Other -Gallon Options
Frequently Asked Questions
How long will the 500 Gallon Doorway Water Tank (31" x 68") last?
Indoors and protected from sun and freeze, a 500-gallon doorway tank easily lasts well beyond fifteen years; sheltering it from the elements is the biggest reason these tanks last so long. The one-piece wall has no seam to fail, and the usual culprits behind early failure — UV and incompatible contents — are simple to avoid in an indoor install.
What chemicals can I store in this tank?
It is made for potable water and food-grade liquids, the standard duty for an indoor reserve. Keep fuels, solvents, and flammables out — especially in an enclosed space — and check any other liquid on a poly compatibility chart, since the resin handles most acids and bases but a few oxidizers attack it.
Does this tank come with a warranty?
Yes — the manufacturer backs it against defects in materials and workmanship under normal use, covering factory faults rather than chemical damage, impact, or inadequate support. Retain the receipt and a picture of the finished install for any warranty claim.
Can I install this tank underground?
No. This is an above-ground doorway tank whose flat wall cannot resist soil pressure; burying it would collapse it and void the warranty. The doorway design is for indoor placement — use a ribbed underground cistern for any below-grade storage.
Buying Considerations
Measure the tightest door and corner on the route — 31 inches needs a genuine 32-inch-plus opening with some margin. Confirm the indoor floor is rated for a full 500-gallon load, place the tank near the plumbing it serves, and arrange a couple of hands for the move, since even empty it is the heaviest doorway tank to maneuver.
Related Products You May Need
Questions? Call (866) 418-1777 — our team knows these products inside and out and can help you select the right tank for your application.
Recommended Tanks for This Guide
Live pricing, updated automatically · estimate freight to your ZIP.
