Norwesco 305 Gallon Vertical Water Tank (40702)
Norwesco makes rotomoulded polyethylene water storage tanks. The black and green vertical tanks are a cylinder with a domed or coned top on a flat base, with gallon marks moulded into the wall. Norwesco publishes dimensions and drawings but no inches-to-gallons chart.
| Model | Norwesco Black or Green Vertical Water Storage Tank, 305 gal (46" dia) |
| Part / model number | 40702 (Black), 41362 (CA Green), 40863 (Dark Green) |
| Rated capacity | 305 US gal |
| Diameter | 46 in |
| Overall Height | 50 in |
| Diameter (drawing, Ø46) | 46 in |
| Overall height (drawing) | 49 in |
| Top cone/shoulder height (drawing) | 12 in |
| Inside or outside? | not stated (web table: 'Diameter', 'Overall Height'; drawings unlabeled outside/inside — appear to be outside) |
“305 46" 50" 16"-(63485) 2"-(63481) 1 1/2"-(63931) Black CA Green Dark Green 40702 41362 40863 (columns: Gallon Capacity, Diameter, Overall Height, Fill Opening, Bottom Fitting, Top Fitting, Color, Part No.)” — Norwesco, retrieved 2026-11-01
Dimension drawing
Gallons by the inch
Norwesco publishes no inches-to-gallons chart. Across the straight part of the wall, each inch of depth in a 46 in diameter tank holds about 7.2 gal — an approximation, because the printed diameter is an outside figure and rotomoulded walls are not perfectly straight. Near the top the dome holds less per inch. The moulded gallon marks on the tank wall are the maker's own reference.
What we found checking the maker's documents
- Drawing overall height 49 in vs web/catalog Overall Height 50 in — discrepancy as printed.
Related: water tank sizes · vertical tank calculator · all manufacturer tanks. Dimensions differ from your tank? Measure it and use the tank volume calculator.
Other sizes: all Norwesco vertical tank sizes.
How to measure the level in this tank
- Open the lid on the top of the tank.
- Put a clean, straight stick through the opening until it touches the floor of the tank. Keep the stick vertical.
- Remove the stick and read the wet line in inches.
- Find the depth in the table below.
- If the tank has moulded gallon marks, compare the result with the marks.
- Close the lid to keep out light, dirt and insects.
Approximate gallons by depth
We modelled the tank from the maker's drawing. The model is a 46 in cylinder with a 37 in straight wall and a 12 in sloped shoulder up to the 16 in lid. The straight wall is the drawing overall height (49 in) minus the top shoulder (12 in). The drawing gives outside sizes, so we scaled every value by 0.989. After this, the full tank equals the rated 305 gal. The scale corrects for the wall on average. It cannot correct for ribs or an irregular dome, so the top rows are the least accurate.
| Depth | Approx. US gallons | % of rated |
|---|---|---|
| 6 in | 43 | 14% |
| 12 in | 85 | 28% |
| 18 in | 128 | 42% |
| 24 in | 171 | 56% |
| 30 in | 213 | 70% |
| 36 in | 256 | 84% |
| 42 in | 290 | 95% |
| 48 in | 304 | 100% |
| 49 in (top) | 305 | 100% |
These values are approximate. If the tank has moulded gallon marks, they are the better reference. For your own measurements, use the dome top tank calculator.
Weight and fill time
At its nominal 305 gal, the water alone weighs about 2,545 lb (1,155 kg). The base under the tank must carry this load over the full footprint.
| Flow rate | Time |
|---|---|
| 5 gal/min | 61 min |
| 10 gal/min | 30 min |
| 20 gal/min | 15 min |
Cite this page
Copy a reference for this page. The data on this page comes from the maker's own documents. Also cite the document in the sources list.
Sri Murugan Systems. (2026, November 1). Norwesco 305 gallon vertical water tank (40702) dimensions. tankvolumecalc.com. https://tankvolumecalc.com/tanks/norwesco/305-gallon-vertical-water-tank-40702/
@misc{srimurugansystems2026norwesco305gallonverticalwatertank40702,
author = {{Sri Murugan Systems}},
title = {{Norwesco 305 Gallon Vertical Water Tank (40702) Dimensions}},
year = {2026},
month = nov,
howpublished = {\url{https://tankvolumecalc.com/tanks/norwesco/305-gallon-vertical-water-tank-40702/}},
url = {https://tankvolumecalc.com/tanks/norwesco/305-gallon-vertical-water-tank-40702/},
note = {tankvolumecalc.com, accessed 2026-11-01}
}Last updated 1 November 2026.
Sources and standards
- Black or Dark Green Water Tanks — 'Black or Green Vertical Water Storage Tanks' table (Norwesco)Norwesco — manufacturerhttps://www.norwesco.com/products/above-ground-tanks/vertical-black-greennot shown
- Norwesco Liquid Storage Tanks catalog (LSTcatalog2024-1.pdf), 'Above Ground Water Only Storage Tanks' table, p.11Norwesco — manufacturerhttps://www.norwesco.com/_site_components/uploads/pdfs/catalogs/LSTcatalog2024-1.pdf2024 (per filename)
- 305 GALLON VERTICAL TANK (Norwesco drawing)Norwesco — manufacturerhttps://www.norwesco.com/_site_components/uploads/pdfs/Vertical/305%20Gallon%20Vertical%20Tank.pdfRev B, REDRAWN 7/3/2013
- Methodology — partial-fill formulas used for the geometric figurestankvolumecalc.comhttps://tankvolumecalc.com/methodology/
Every linked source above was retrieved and checked on 2026-11-01.