The Norwesco 325 Gallon Underground Water Storage Cistern is a buried polyethylene cistern built to hold water below grade in a compact 54-inch cube footprint. If you are sizing buried storage for a rural home, a remote cabin, a fire-water reserve, or rainwater capture, this 325-gallon cistern gives you a self-contained underground water store that stays out of sight, out of the sun, and protected from freeze in cold-climate installs. The tank measures 54 inches in height, width, and length, and is molded in white polyethylene.
Will it hold your water and handle the load?
At 325 gallons of capacity, a full tank of plain water weighs roughly 2,710 lb, and the tank carries a maximum rated contents weight of 5,150 lb. Read that 5,150 lb as contents-only headroom, not a structural burial-load spec: it is the weight of liquid the tank body is engineered to bear, which is why the specific-gravity rating is listed at 1.9 rather than the 1.0 of water alone. For plain water storage you are well inside that envelope, and SG 1.9 is the high-rated point in Norwesco's water line. Footprint is 54.0 x 54.0 inches, so plan a square excavation around the 54-inch footprint plus even bedding underneath and working clearance on all sides. Burial tanks live or die on backfill discipline and even bedding support, so size your hole and bedding before the tank arrives. Our Tank Sizing Calculator and Tank Sizing Guide help you confirm 325 gallons is the right volume for your draw rate and storage goals before you dig.
Plan the install before you backfill
Because this is an underground cistern, the install sequence is the part most people get wrong. The right order is excavate to plan, bed evenly, set the tank, then fill it with water as you backfill in lifts so internal and external pressure stay balanced. Inlet, outlet, and lid or manway configuration on a buried tank can't be changed once backfill goes in, so confirm port placement by phone before you order rather than guessing from a generic diagram. Our hydrostatic test methodology guide walks through water-fill discipline, settlement monitoring, and fitting leak detection at acceptance. If this cistern feeds a rural or remote private fire-protection reserve, our fire-water reservoir design guide covers NFPA 22 sizing and cold-climate freeze protection, and our water reuse topology guide is the reference if you are aggregating grey-water, rainwater, or HVAC condensate.
The mistake to avoid
The most common error with a buried cistern is treating it like an above-ground tank. Never backfill an empty underground tank, and never leave it empty in saturated ground without following the manufacturer's burial and ballast instructions. The specific-gravity rating of 1.9 describes the contents weight the body is rated for, not a license to skip even bedding or balanced backfill. Confirm your bedding material, fill-as-you-backfill sequence, and any required surrounding support before the tank goes in the hole. Get this right and a polyethylene cistern is a low-maintenance underground water store for decades.
This Norwesco underground water storage tank ships LTL freight, quoted live to your ZIP, from the nearest of 8 Norwesco plants nationwide to keep your lane short: Griffin, GA; Hanford, CA; Lancaster, OH; Owego, NY; Shawnee, OK; St. Bonifacius, MN; Tooele, UT; and Washougal, WA. Get a real number for your address with our Freight Cost Estimator, or call 866-418-1777 and we will quote the cistern and walk through your underground install.
