The Norwesco 500 Gallon Above Ground Septic Holding Tank is a black polyethylene holding tank built for above-ground septic and wastewater collection where a buried tank is not the right answer. It is a holding tank, not a treatment or leaching tank - it collects effluent and is pumped out on a schedule, it does not treat or disperse. The number that matters most here is the 1.9 specific gravity rating. At 500 gallons of plain water the contents weigh roughly 4,170 lb, but the 1.9 SG rating means the shell is engineered to safely contain contents up to about 7,923 lb. A standard 1.0-SG water tank rated only to the ~4,170 lb water weight would be under-spec for dense septic effluent, sludge, and solids-laden wastewater, where contents routinely run heavier than water. That extra rated headroom is exactly why this tank is the correct choice for this service.
Will it work for your install?
This is a low-profile holding tank: 22 in tall, 52 in wide, and 130 in long, giving a 52.0 x 130.0 in footprint. The low 22-inch height keeps it stable and makes gravity-fed inlet plumbing manageable, while the long footprint spreads the load. The drawing shows a thread for an 8" lid, so that threaded port is your single point of access - every inlet, outlet, vent, and pump-out connection has to adapt to or pass through it. Confirm the thread spec and the seal that ships with the 8" lid against the technical drawing on this page before you order any adapters. Use the Tank Sizing Calculator and Tank Sizing Guide to confirm 500 gallons matches your daily flow and pump-out schedule. Because this sits above ground, the supporting surface carries the full loaded weight: design your pad for the full rated load of about 7,923 lb, not the ~4,170 lb water figure. Our guide on concrete pad sizing for above-ground polyethylene tanks walks through the ACI framework for that.
The mistake to avoid
The most common error on a septic holding tank is treating capacity as the only number. The 8" threaded lid is your single point of access, so any pump-out connection, vent, and inlet has to be planned through or around it - retrofitting a second penetration in the field is far harder than specifying it correctly up front. If this tank crosses into Canadian jurisdiction or you need a code-approved septic install, verify the approval scope first; our write-up on Norwesco IAPMO and CSA B66 septic tank approvals covers US plumbing-code versus cross-border scope. For operators tracking throughput, the tank gauge calibration guide adapts UST accountability discipline to above-ground poly tanks. And if you are still weighing whether this should sit above or below grade, above-ground vs below-ground tank selection lays out the decision by service type.
Freight
This 500 gallon Norwesco septic holding tank ships LTL freight, quoted live to your ZIP from the nearest stocking plant - either Fairfield, TX or St. Bonifacius, MN. Use the Freight Cost Estimator for a freight estimate to your address, or call us at 866-418-1777 and we will route it from the closest plant to keep transit and cost down. Listed before freight; LTL is quoted separately per ZIP.
