305 Gallon Plastic Water Storage Tank: Complete Buyer's Guide
A compact 305-gallon black potable-water tank in a squat, stable 50-by-46-inch body — the right size for a cabin, a small household backup, or a livestock trough supply. FDA-approved Norwesco polyethylene, pigmented black to block light and algae, with a 2-inch outlet and a 1.5-inch inlet installed and ready to plumb.
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.
Product Overview
The 305 Gallon Plastic Water Storage Tank is the small, easy-to-place potable tank for modest water needs: a weekend cabin's supply, a household emergency backup, a small irrigation buffer, or stock watering. At 50 inches tall on a 46-inch base it sits low and steady, and at just 64 pounds empty one or two people can position it without equipment.
The black wall does real work at any size — blocking sunlight to discourage algae and keep the stored water clearer between uses. Even at 305 gallons the tank ships ready to connect, with a factory 2-inch outlet near the base and an included 1.5-inch inlet, and the 16-inch lid is generous for its size, easily accepting a float valve or a small pump.
Filled with water at the rated 1.1 specific gravity — about 9.2 pounds per gallon — the tank reaches roughly 2,862 pounds, around a ton and a half over the small, broad base. Because water is light, the squat shape stays very stable when full. The factory does not require you to add fittings — fill and draw are already in place.
With no seam to fail, FDA approval for potable and food-grade use, and Norwesco's 3-year defect warranty, the tank is built to last. Every unit is checked before dispatch.
Technical Drawing
Official Norwesco technical drawing — 305 Gallon Plastic Water Storage Tank
Key Features and Specifications
- 305-gallon capacity — sized for safe potable water storage
- Constructed from virgin linear polyethylene (HDPE) with 1.1 specific gravity rating — handles liquids up to 9.2 lbs/gal
- 50" tall x 46" diameter — compact vertical footprint
- 64 lbs empty, approximately 2,862 lbs when full at rated specific gravity
- 2 NPT outlet fitting — factory installed and leak-tested
- 1.5 NPT inlet fitting included
- 16" lid opening for fill, venting, and interior access
- FDA approved for potable water and food-grade liquid contact
- 3 Year Warranty from Norwesco against manufacturing defects
- UV-resistant black pigmentation provides maximum outdoor durability and inhibits algae growth in stored liquids
- Rated for continuous service up to 120 F / 48 C
- Seamless one-piece rotational molding — no seams, no welds, no leak points
- Manufactured by Norwesco — a leading name in rotomolded polyethylene tanks
- Place on a firm, level surface free of rocks or sharp objects that could damage the tank bottom. Ensure adequate ventilation if stored chemicals produce vapors
- Ships via LTL freight on a pallet — residential delivery with lift gate available
Installation and Setup Guide
The 305 water tank is simple to set thanks to its low, light, stable form, and the main extra consideration is keeping the drinking water clean through good connections and protection from contamination.
Site Preparation
Set it on a firm, flat surface that supports the 46-inch base — a slab, a paver bed, or a compacted pad. Keep it level so the squat tank loads its base evenly, and clear any grit from beneath. Site it where surface runoff drains away from the lid and connections rather than toward them, protecting the stored water.
Placement and Connections
Use the factory 2-inch outlet for draw and the included 1.5-inch inlet for fill, with potable-rated NSF-listed PVC or food-grade fittings and a short flex section before rigid pipe. Fit a screened, insect-proof vent in the lid and keep the fill point protected. A foot and a half of clearance is plenty for inspection at this size.
Venting
The tank must breathe through fill and draw while keeping insects and dust out of the potable supply. A small screened lid vent sized to your flow rates handles both, ensuring no vacuum forms on the wall during a quick draw.
Maintenance and Long-Term Care
A little routine care keeps the water safe to drink. The small size makes turnover easy, which itself helps keep the water fresh.
Quarterly Inspection Checklist
- Water quality: Check for cloudiness, sediment, or odor that would signal stagnation in a small backup tank.
- Shell and base: Look for any bulge or a flat spot at the base, and confirm the pad stays level.
- Fittings: Examine the 2-inch outlet and the 1.5-inch inlet for dampness and hand-tighten as required.
- Vent and lid: Check that the screen is sound and the lid seals to keep insects and debris out.
Cleaning
Drain and sanitize at least annually — easy on a tank this size. After clearing sediment, sanitize with a chlorine solution at about a quarter cup of unscented household bleach per fifteen gallons, hold it a couple of hours, then drain and flush with fresh water until no chlorine odor remains. Refill with clean potable water; on a small backup tank, refreshing the water periodically keeps it ready when you need it.
UV and Weather Protection
The black pigment provides UV protection and algae defense in one. In freezing climates, protect exposed plumbing and do not let a full tank freeze solid, since ice expansion can stress the shell. A small tank like this is also easy to move under cover for the winter if needed.
Alternatives and Comparisons
This small black water tank is the easy, stable choice for modest potable storage. A slim 305 chemical tank exists in white at 1.5 specific gravity, but it is built for chemicals and not finished for drinking water — choose this black water tank for water. For more reserve, step up to a 550 or 1,550 black water tank. The rule stays constant: water in black to fight algae, chemicals in white at the heavier rating.
Frequently Asked Questions
How long will the 305 Gallon Plastic Water Storage Tank last?
Fifteen to twenty years of dependable potable service is realistic with a level base and routine sanitizing. The seamless mold has no joints to fail, and the black pigment gives UV protection and algae resistance. The usual life-shorteners are a poor foundation, freezing a full tank, or impact; chemical attack is not a concern with clean water.
What chemicals can I store in this tank?
It is made and FDA-approved for potable water and food-grade liquids, which is exactly what it is for. Rated to 1.1 specific gravity, it is not built for heavier agricultural or industrial chemicals; for those, choose a white liquid-storage tank rated for them rather than this water tank.
What kind of foundation does a 305-gallon tank need?
A full load is about 2,862 pounds over the small 46-inch base. A firm, level slab, paver bed, or compacted pad that supports the diameter is sufficient. Keep the surface flat and clear of grit, and grade the area so runoff drains away from the connections.
Does this tank come with a warranty?
Yes — a three-year manufacturer warranty from Norwesco covers material and workmanship problems, pinholes included. It excludes damage from freezing a full tank, a poor base, or impact. Retain proof of purchase and a few setup photos to back any future claim.
Can I install this tank underground?
No. This is an above-ground water tank; its flat walls cannot resist burial pressure and would collapse. For below-grade drinking-water storage, choose an underground cistern with ribbed, reinforced walls.
Buying Considerations
Confirm three points before placing your order. First, placement — at 50 inches tall and 64 pounds empty it goes nearly anywhere, but give it a flat, supportive base. Second, plumbing — confirm the included 2-inch outlet and 1.5-inch inlet suit your setup, with potable-rated connections. Third, delivery — it ships on a pallet and a lift gate handles unloading. Call us to arrange delivery.
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