120 Gallon Plastic Water Storage Tank: Complete Buyer's Guide
120 Gallon Plastic Water Storage Tank from Norwesco.
Technical Drawing
Official Norwesco technical drawing — 120 Gallon Plastic Water Storage Tank
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.
- FDA 21 CFR 177.1520 — Olefin polymers. The food-contact regulation the FDA-grade resin in this tank is compounded to meet.
- Specific gravity rating 1.1 — the tank is engineered for liquids up to 1.1× the density of water (water is about 8.34 lb/gal). Confirm your fluid’s SG before storage.
Installation and Setup Guide
The 120-gallon water tank is small enough to install single-handed and modest enough in weight that no special foundation is required. The job is simply to give the bottom firm, level, continuous support so the water load presses straight down rather than concentrating on a high point.
Where to Put It
Set the tank on a hard, level surface free of rocks and sharp debris — a swept concrete floor indoors, or a small slab or compacted, drained pad outdoors. Check the surface with a level before the tank goes down; even a small tank tips its water line and presses unevenly on the wall if the base slopes. Choose a spot that drains so standing water never works under the tank.
Connections
Plumb your draw line to the outlet and, if you fill from the top, a float valve through the lid keeps it from overflowing. Keep the first foot of the outlet connection flexible so the polyethylene can move with temperature without stressing the fitting, and add a shutoff valve so you can isolate the tank for cleaning.
Venting
If the tank is plumbed closed, fit a screened breather in the lid so air can enter as you draw water out. Even a 120-gallon tank can dent if a pump empties it faster than air comes in, so size the vent to your draw and keep the screen clear to protect the stored water.
Maintenance and Long-Term Care
A small potable tank is the simplest of all to keep clean, because the modest volume turns over fast and the whole tank is light enough to drain and refill in minutes.
Quick Checks
- Wall and fitting: Glance over the wall for any bulge and the outlet for weeping every so often, and hand-snug the fitting if it has loosened.
- Lid and screen: Confirm the lid seats fully and the vent screen is intact so nothing reaches the water.
- Base: Make sure the tank still sits level and has not shifted on its surface.
Sanitizing
With only 120 gallons you can refresh the tank often. Empty and rinse the floor, then disinfect using the potable dose of a quarter cup of unscented bleach per fifteen gallons, let it stand two hours in the filled tank, and flush until the chlorine odor is gone. For a reserve tank that sits idle, run this at least yearly and rotate the water so it stays fresh.
Indoor and Outdoor Use
Kept indoors, the tank sees no sunlight and essentially never ages from UV. Outdoors, the molded-in UV package carries it for years; an occasional look at the sun-facing side is plenty. In freezing weather a small tank ices quickly, so drain it or keep it warm where winters bite.
Alternatives and Comparisons
At 120 gallons the decision is how much reserve you need versus how little space you can give it.
Sizing around it: A 120-gallon tank is a tidy step up from barrels and jugs, giving you a single sealed, plumbed supply instead of a row of containers to refill by hand. If you find yourself topping it off constantly, a 165- or 220-gallon tank adds buffer for only a little more footprint. If even this is more than your space allows, a smaller upright drops in. Where light blocking and a sealed lid matter — for drinking water especially — a proper tank beats open or translucent containers every time.
Other -Gallon Options
Frequently Asked Questions
How long will the 120 Gallon Plastic Water Storage Tank last?
With a level base and use as a water tank within normal polyethylene temperature limits, this tank gives 15 to 20 years and often more, since small tanks lead an easy life. The molded-in UV protection resists sun whether the tank is indoors or out, and the one-piece body has no seam to fail. Periodic draining and sanitizing keeps the water fresh across that span.
What chemicals can I store in this tank?
It is an FDA-approved potable-water tank, suited to drinking water, livestock, and small-scale irrigation, plus water-based liquids within its rating. It is not for fuels, solvents, or harsh chemistry. For chemical storage, use a dedicated 1.5-SG liquid tank and verify the product against a compatibility chart — a water tank is the wrong vessel for chemicals.
Does this tank come with a warranty?
Yes. Under normal use Norwesco's 3-year warranty handles molded-in manufacturing faults, but not damage from a poor base, overfilling, incompatible chemicals, or impact. Keep your receipt for any claim.
Can I install this tank underground?
No. The tank wall is not engineered to resist soil pressure, so burying it would risk collapse and void the warranty. For below-grade water storage, choose one of our reinforced underground cisterns.
Buying Considerations
Three quick points before this 120-gallon tank ships. First, access: it is compact, but measure your path if it is headed indoors or into a tight utility space. Second, your plumbing — confirm the outlet thread and plan a top fill or a tee for filling. Third, delivery: a tank this small ships easily on a pallet and one person can handle it on arrival. Listed at $390.00 before freight, with a quote to your ZIP.
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