The Norwesco 300 Gallon Above Ground Septic Holding Tank (SKU N-44234-CA) is a low-profile black polyethylene holding tank built for above-ground septic and wastewater containment. At just 16 inches of overall height with a 56" x 95" footprint, it sits low enough to fit under decks, in crawl-tight equipment yards, and in tight setbacks where a vertical tank will not clear an opening. The 300-gallon capacity and 1.5 specific gravity rating make it a working choice for septic holding, pump-out service, and seasonal or remote sites that need a reliable above-ground reservoir.
Does it work for your site?
This is a 300 gallon holding tank measuring 16" high, 56" wide, and 95" long, molded in black polyethylene with a 1.5 specific gravity rating. The 1.5 SG rating means the wall is built to carry contents heavier than water, which already covers typical septic effluent. Measure your clearance against the 16-inch overall height before you commit to a spot, then plan your contents weight before you fill. Design the pad for the loaded weight: 2,502 lb full of water, and up to 3,753 lb at the maximum rated contents weight against the 1.5 SG rating. Use the Tank Sizing Calculator and Tank Sizing Guide to confirm 300 gallons matches your inflow and pump-out cadence. You can also see the technical drawing on this page for the overall dimensions.
Plumbing and base — the two mistakes to avoid
The first mistake is ordering without confirming how the tank is plumbed. Inlet, outlet, and lid/fitting configuration drive how this tank ties into your inflow and pump-out lines, so confirm the configuration for your plumbing before ordering — call 866-418-1777 and we will verify it with you. The second mistake is undersizing or under-leveling the base. With up to 3,753 lb of rated contents resting on a 56" x 95" footprint, a poured pad or compacted, level support across the full footprint is not optional — point loading or an uneven base stresses the shell. Our guide on concrete pad sizing for above-ground polyethylene tanks walks the ACI 360R-10 framework, and if you track volume for pump-out scheduling or audit records, the tank gauge calibration guide shows how to keep readings defensible.
Approvals and placement
Septic approvals are jurisdiction-specific, so confirm requirements with your local authority before installing. For Canadian cross-border or IAPMO/CSA questions, our writeup on Norwesco IAPMO and CSA B66 septic tank approvals covers the scope difference between Canadian and US plumbing codes. If you are still weighing whether to go above-ground or below, the above-ground vs below-ground selection guide lays out the trade-offs for septic and holding service.
This tank ships LTL freight, quoted live to your ZIP. Get your number with the Freight Cost Estimator or call 866-418-1777 and we will quote the delivery for you. Whether you are searching for a 300 gallon septic tank, a Norwesco holding tank, or a low-profile 300 gallon tank for above-ground service, this one is sized to do the job.
