Large Water Tanks, 20,000L to 150,000L
Underground fibreglass (FRP) water storage tanks in sizes from 20,000L to 150,000L, and larger volumes from connected tanks. Made in Australia by Mullaly.
Large fibreglass water tanks that go underground
Most results for a 50,000 litre water tank, or for huge water storage tanks in general, are round above-ground tanks in poly or corrugated steel. Mullaly tanks are different. They are ribbed fibreglass tanks built to go underground, with select designs for above-ground installation. The water is stored out of sight and the surface stays free for buildings, yards, car parks and landscaping.
Single tanks run from 5,000L up to 150,000L for some applications, in diameters up to 3.28m, with single or double walls. That covers the common large sizes people search for, such as a 30,000 litre water tank, a 50,000L water tank or a 100,000 litre water tank. Where a site needs more than one tank holds, several tanks are connected with PVC or fibreglass pipework.
Large water tank capacities
| Capacity | Kilolitres | Cubic metres | Rain on a 1,000m² roof to fill it |
|---|---|---|---|
| 20,000L | 20kL | 20m³ | 20mm |
| 30,000L | 30kL | 30m³ | 30mm |
| 50,000L | 50kL | 50m³ | 50mm |
| 85,000L | 85kL | 85m³ | 85mm |
| 100,000L | 100kL | 100m³ | 100mm |
| 150,000L | 150kL | 150m³ | 150mm |
One kilolitre is 1,000L, and one cubic metre is also 1,000L, so engineers' storage figures in m³ convert directly. Each millimetre of rain on a square metre of roof gives one litre before losses. The largest single-tank sizes are for some applications only; tell us the volume and we will confirm whether it is one tank or a set of connected tanks.
Tank options
Construction
- Fibreglass (FRP) with integral, high-profile ribs
- Single wall or double wall
- Resin with no fillers, and no lining or coating needed
- Designed to be 100% watertight
Installation
- Underground, and select above-ground installations
- Not limited by the water table
- Ribs designed for the soil and surface loads on each site
- Single tanks, or several tanks connected with PVC or fibreglass pipework
Fittings
- Access risers and manways
- Inspection ports and FRP inspection ladders
- Baffles
- Inlet, outlet, overflow and vent points
What large water tanks are used for
Mullaly large water tanks hold water and wastewater for councils, utilities, commercial and industrial sites, and remote projects. Common uses are:
- Fire water storage for sprinkler systems and dry-hydrant connections
- Rainwater harvesting and reuse for toilet flushing and irrigation
- Stormwater retention and detention
- Overflow and emergency storage for sewage pump stations
- Potable water. Mullaly tanks are certified to AS/NZS 4020 for contact with drinking water
- Factory wash-down and other non-potable water
- Water storage for remote sites and accommodation villages
Mullaly FRP emergency storage tanks are covered by the same WSAA product appraisal (PA 1020 Issue 4, current to 2031) as our sewage pump stations.
Why fibreglass for a large tank
Rust and corrosion proof
Fibreglass resists both the stored water and the surrounding soil, so there is no steel to rust and no coating to repair.
Watertight
Designed to be 100% watertight, which keeps stored water in and groundwater out.
Ribbed for strength
Integral, high-profile fibreglass ribs are part of the tank wall and are designed for the soil and surface loads on each site.
High groundwater
Mullaly underground tanks are not limited by the water table.
No ongoing maintenance
The tank structure needs no ongoing maintenance or inspections.
Light for its size
A large-capacity tank ships on one truck bed and is easy to install in remote places and tight footprints.
Getting a large tank to site
A tank of 50,000L or more is a big object to move, so transport and lifting are part of the choice. Because fibreglass is light for its size, a large-capacity Mullaly tank goes on one truck bed. At Sydney Airport Pier B, two 85kL overflow storage tanks and a combined wet well, valve pit and macerator pump station arrived on three semi-trailers. They were lifted into place once excavation was done, then ballasted and backfilled.
Tell us the groundwater level, soil conditions and any surface loads over the tank when you ask for a quote. Installation follows the Mullaly water storage tank installation manual. If you are comparing a fibreglass tank with precast, see fibreglass vs concrete water tanks.
Water storage tank photos
Large water tank questions
What is the largest water tank Mullaly makes?
Single tanks go up to 150,000L for some applications, in diameters up to 3.28m. Larger volumes are made up of several tanks connected with PVC or fibreglass pipework.
Do you make a 50,000 litre water tank?
Yes. 50,000L sits within the Mullaly single-tank range of 5,000L to 150,000L, as do 30,000L and 100,000L tanks. Tell us the volume and use, and we will recommend the tank.
Are these above-ground tanks?
Mullaly tanks are designed mainly for underground installation, with select designs for above ground. If you need a round above-ground tank in poly or steel, this is a different product.
How many litres is 50kL or 50m³?
Both are 50,000L. One kilolitre and one cubic metre each equal 1,000L.
Can a large tank hold drinking water?
Mullaly tanks are certified to AS/NZS 4020 for contact with drinking water. See our potable water tanks page for details.
Can large tanks be connected together?
Yes. Single-tank and multiple-tank installations are available, connected with PVC or fibreglass pipework.
How is a large tank delivered?
Fibreglass is light for its size, so a large-capacity tank ships on one truck bed and can be installed in remote places and tight footprints.
Downloads
- FRP water storage tank technical data sheet (PDF)
- Single-wall water storage tank installation manual (PDF)
More on the range is on our underground water tanks and industrial water tanks pages, and in the resource centre.
Download the water storage tank brochure
Enter your email and the brochure opens straight away. We will also email you the link.
Request a quote for a large water tank
Tell us the volume, how the water will be used and the site conditions, and we will recommend a tank or set of tanks. We reply to every enquiry within 2 business days.
Or call 02 4964 8270 or email sales@mullaly.com.au