Norwesco 325 Gallon Plastic Underground Water Storage Cistern Tank

Where a 325 gallon cistern earns its place

This size suits a household rainwater catch under two or three downspouts, a buffer between a slow well and a pressure pump, a reserve at a cabin or a remote site, or a greywater holding point ahead of treatment. Buried polyethylene stays cool, keeps light off the water so algae does not get a start, and does not take up yard or freeze in a hard winter when it is set below the frost line. The trade is that a buried tank is only as good as its hole: it needs a bed of compacted sand or pea gravel, backfill brought up in lifts around the sides, and a site where groundwater will not float an empty tank out of the ground. Our notes on rainwater and reuse water storage layouts and fire water reserves for rural and remote sites cover how a cistern fits into each system. For the volume, run the tank sizing calculator and read the tank sizing guide.

What to check before you buy

1. Burial depth and the riser. The manway is 20 inches across. Norwesco makes one of five parts to bring it to grade, each sold separately and one per manhole: a 6 inch extension (N-63832), a 15 inch extension (N-63833), a 24 inch extension (N-63834), a 23 inch riser with a 12 inch lid (N-63831) or a 36 inch riser with a 6 inch lid (N-63830). Measure from the top of the tank at its set depth to finished grade and pick the one that lands the lid where you want it.
2. Openings. No outlet fitting is listed for this tank, so the inlet, outlet and overflow are cut and fitted on site to suit your plumbing. Tell us the pipe sizes you are running and we will put the bulkhead fittings on the same order.
3. The hole. Flat, level bedding, no rock in contact with the shell, backfill compacted in lifts as the tank is filled with water to keep the walls supported evenly. Keep vehicles off the area unless a slab designed for the load is poured over it.
4. Drawing. Norwesco's drawing for this cistern is linked under Technical Drawing on this page and shows the manway position and the overall shape for laying out the excavation.

Sizes nearby

One step down: the 250 gallon underground cistern. One step up: the 575 gallon underground cistern. All three take the same riser and extension parts, so a site with two tanks at different depths still orders from one list.

Shipping and receiving

The tank ships LTL freight, 54 by 54 by 54 inches on a pallet, 164 lb as packed, from the nearest of Norwesco's plants in Griffin, Georgia, Hanford, California, Lancaster, Ohio, Owego, New York, Shawnee, Oklahoma, St. Bonifacius, Minnesota, Tooele, Utah or Washougal, Washington. The listed price is before freight; the freight cost estimator gives the lane cost to your ZIP, or request a written quote. Risers and fittings ordered with the tank travel with it. At the tailgate, check the part number against 41321 on the bill of lading and look over the whole shell for transit damage before the driver leaves. Before backfilling, fill with water and hold it; our guide to water-fill acceptance testing of a new tank gives the method, and a leak found in an open hole is a nuisance where the same leak under backfill is a dig.

Questions before you order? Call 866-418-1777.