Water Tank Sizes and Dimensions: A Chart for Every Capacity and Shape

How big is a 5,000 litre water tank? It depends on the shape. A squat round tank is 2,175mm across and 1,750mm high. A slimline holding the same amount is just 940mm wide but 3,080mm long and 2,170mm high. An underground tank is only 950mm high, but it takes up 2,780 × 3,500mm of ground. Water tank sizes vary just as much at every other capacity. This guide lists the nominal dimensions of every tank we sell, from a 360 litre round tank to a 34,000 litre one, so you can check what fits before you choose the right water tank for you.

Most people start with a capacity in mind, such as 3,000, 5,000 or 10,000 litres, and then work out which shape fits. This chart puts the main options at each capacity side by side.

Water tank sizes by capacity: every shape compared (nominal dimensions, width × length × height)

Capacity	Round poly	Slimline poly	Underdeck / underground poly	Steel (Kingspan Water)
About 1,000L	R1200 round: 1,070mm diameter × 1,555mm high	SL1180UR: 600 × 1,350 × 2,130mm	UD1000 underdeck: 1,200 × 1,720 × 710mm	Steel slimline 1,000L: 550 × 1,300 × 1,560mm
About 2,000L	R1800sq round: 1,560mm diameter × 1,220mm high	SL2000UR: 625 × 2,250 × 1,930mm	UD2000 underdeck: 1,200 × 2,350 × 870mm	Round 2,000L: 1,200mm diameter × 1,860mm high
3,000L	R3000 round: 1,600mm diameter × 1,850mm high	SL3000UR: 700 × 2,660 × 2,130mm	LU3000 / LUD3000: 2,420 × 2,520 × 900mm	Round 3,000L: 1,500mm diameter × 1,860mm high
5,000L	R5000sq: 2,175mm diameter × 1,750mm high R5000ur: 1,800mm diameter × 2,470mm high	SL5000UR: 940 × 3,080 × 2,170mm ML5000SQ: 1,160 × 3,160 × 1,850mm	LU5000 / LUD5000: 2,780 × 3,500 × 950mm	Round 5,000L: 1,900mm diameter × 1,860mm high
About 10,000L	R10000 round: 2,510mm diameter × 2,350mm high	Not available	Not available	Round 10,000L: 2,700mm diameter × 1,860mm high
About 20,000L	R18200: 3,400mm diameter × 2,540mm high R22700ur: 3,550mm diameter × 2,835mm high R22700sq: 4,180mm diameter × 2,220mm high	Not available	Not available	Round 20,000L: 3,400mm diameter × 2,250mm high Round 22,900L: 3,550mm diameter × 2,320mm high

The squat and upright choice matters most around 5,000 and 22,700 litres:

• At 5,000 litres: the R5000sq is 375mm wider than the R5000ur, but 720mm lower. That height difference can decide whether a tank fits under eaves or a window.
• At 22,700 litres: the squat version is 4,180mm across and the upright is 3,550mm. The upright needs 630mm less width but stands 615mm taller.

For capacities above 10,000 litres, also check delivery access before you commit. The R22700sq and R34000 are delivered by trailer only and need 5m of overhead clearance. Our round water tank prices guide has the full delivery details for each model.

Slimline tanks are rectangular. They’re designed to sit flat against a wall or fence, where a round tank would take up too much of the path.

Water tank sizes: slimline poly tanks, width, length and height (nominal)

Model	Capacity	Width	Length	Height
SL450	450L	600mm	1,170mm	920mm
SL650SQ	650L	600mm	1,350mm	1,250mm
SL1180UR	1,180L	600mm	1,350mm	2,130mm
SL1650SQ	1,650L	700mm	2,660mm	1,250mm
SL2000UR	2,000L	625mm	2,250mm	1,930mm
SL3000UR	3,000L	700mm	2,660mm	2,130mm
SL3000SQ	3,000L	760mm	3,040mm	1,865mm
SL4000UR	4,000L	920mm	2,600mm	2,170mm
SL4000SQ	4,000L	955mm	3,090mm	1,890mm
SL5000UR	5,000L	940mm	3,080mm	2,170mm
ML5000SQ	5,000L	1,160mm	3,160mm	1,850mm

Width is usually the measurement that decides it. The narrowest slimlines, the SL450, SL650SQ and SL1180UR, are 600mm wide. At 3,000 litres, you can choose between 700mm and 760mm wide, and at 5,000 litres between 940mm and 1,160mm.

The “UR” (upright) and “SQ” (squat) models work the same way as the round tanks. The SL3000UR is 2,130mm high, while the SL3000SQ is 265mm lower but 60mm wider and 380mm longer. For prices on each model, see our slimline water tank prices guide.

When there’s no room above ground, these tanks go under a deck or into the ground. They’re low and flat, so their footprint is larger than other shapes for the same capacity.

Water tank sizes: underdeck and underground poly tanks (nominal)

Model	Capacity	Width	Length	Height
UD1000 underdeck	1,000L	1,200mm	1,720mm	710mm
UD2000 underdeck	2,000L	1,200mm	2,350mm	870mm
LUD3000 underdeck	3,000L	2,420mm	2,520mm	900mm
LU3000 underground (yard or driveway)	3,000L	2,420mm	2,520mm	900mm
LUD5000 underdeck	5,000L	2,780mm	3,500mm	950mm
LU5000 underground (yard or driveway)	5,000L	2,780mm	3,500mm	950mm

The LU (underground) and LUD (underdeck) tanks share the same dimensions at 3,000 and 5,000 litres. The UD1000 and UD2000 are smaller underdeck options, and at 710mm and 870mm high, they suit lower decks. The UD2000 is also designed to fit between the piers of existing decks.

For an underground tank, the hole needs to be bigger than the tank to allow for bedding and backfill. Follow the installation instructions for your model. Our underground water tank prices guide covers the yard and driveway versions.

We also supply round and slimline steel tanks made by Kingspan Water. Round steel tanks run from 2,000 to 27,000 litres. Most sizes are 1,860mm or 2,020mm high, so a larger capacity in steel usually means a wider tank rather than a taller one.

Water tank sizes: round steel tanks by Kingspan Water, diameter and height (nominal)

Capacity	Diameter	Height
2,000L	1,200mm	1,860mm
3,000L	1,500mm	1,860mm
4,000L	1,700mm	1,860mm
5,000L	1,900mm	1,860mm
10,000L	2,700mm	1,860mm
15,000L	3,100mm	2,020mm
18,000L	3,400mm	2,020mm
20,000L	3,400mm	2,250mm
22,900L	3,550mm	2,320mm
27,000L	3,400mm	3,010mm

The 27,000 litre steel tank is the exception. At 3,010mm high, it fits 27,000 litres onto the same 3,400mm diameter as the 20,000 litre tank. Slimline and Modline steel tanks run from 1,000 to 7,000 litres in 20 shapes, from 550mm wide. Our steel water tank prices guide lists the dimensions and price of every round, slimline and Modline steel model.

Before you order, measure your space and compare it with the chart:

1. Measure the full footprint. For a round tank, compare the diameter with the shortest side of your space. For a slimline, check the width and the length.
2. Check the height. Look for eaves, windows, gutters, fences and anything overhead. Remember the tank sits on a base, which adds to its height.
3. Allow room around the tank. You’ll need space for the inlet, overflow, outlet, pump and access for maintenance. Our base preparation guide explains what the tank needs to sit on.
4. Check the delivery path. The tank has to get to the spot. Measure gates, side passages and overhead clearance on the way in.
5. Allow for small variations. All dimensions here are nominal. Rotomoulded tanks can vary slightly from the listed size, as our note on why tank dimensions are nominal explains.

If you’re still deciding how many litres you need, start with our guide to what size water tank to buy, then come back to this chart to find the shape that fits.

It depends on the shape. A round squat tank (R5000sq) is 2,175mm in diameter and 1,750mm high. A round upright (R5000ur) is 1,800mm across and 2,470mm high. A slimline (SL5000UR) is 940mm wide, 3,080mm long and 2,170mm high.

Our R10000 round poly tank is 2,510mm in diameter and 2,350mm high. A 10,000 litre round steel tank is 2,700mm in diameter and 1,860mm high.

The R3000 round tank is 1,600mm in diameter and 1,850mm high. The SL3000UR slimline is 700mm wide, 2,660mm long and 2,130mm high. The LU3000 underground tank is 2,420 × 2,520mm and 900mm high.

Our narrowest poly slimlines are 600mm wide, from 450 to 1,180 litres. In steel, the Standard Slimline (1,000 and 1,500 litres) and the 2,000 litre Skinny are 550mm wide.

About 22,700 litres. The R22700 is sold as a 5,000 gallon tank, using imperial gallons of about 4.55 litres each.

Found the size that fits? Browse the full water tank range or call 1300 826 532 to check dimensions and delivery access for your site.