A 5000 gallon tank occupies an unusual middle ground that is neither standard domestic rooftop tank nor widespread, but is more prevalent in villas, small commercial buildings, labor camps and irrigation systems throughout the UAE. The water quality and structural requirements are reality at about 19,000 liters, and it’s at this size that the distinction between a well-designed precast reinforced concrete tank and a cheaper one becomes apparent. So, what does matter and why has the reinforced precast method become the preferred manner of construction for a 5000 gallon pre-cast concrete tank throughout the region?
The Advantages of Precast Reinforced Concrete at this Capacity
Because a tank at 5000 gallons will contain a considerable static load of water (about 19 tonnes when full) it cannot be constructed of a container which happens to be watertight, but must be strong enough to resist compression and be suitably reinforced.
Why the UAE’s summer heat can’t melt the plastic/fibre glass, and why UV exposure doesn’t eat away at concrete like it does over time on metal tanks, are all reasons why concrete is well suited here.
In addition to the material, there is an added benefit of precast manufacturing.
Manufacture of the tank will ensure control and uniformity of the concrete mix, reinforcement and the curing cycle; the tank will also be cured to the designated strength in the factory, rather than relying on the conditions at the project site.
If the water collected inside the tank containing potable or process water will be under constant hydrostatic pressure, this consistency will decide whether the tank will remain watertight for decades or will begin to show hairline cracks in a few years.
1. Wall Thickness and Reinforcement Design
The pressure against the wall of a 5000 gallon tank is always pushing outwards and is greatest at the bottom and decreases along the way to the top when the tank is full.
The thickness of the wall should be designed for that pressure profile and the spacing of reinforcement steel should be determined in that way, not as a uniform thickness all over.
Typical structural issues begin at the base of the walls, usually when they are smaller than the tank or there is not enough reinforcement.
2. Concrete Grade and Water-Tightness
Not every type of concrete is suitable for use in water storage.
A tank should be made of a low percolating, high strength concrete, with controlled water-cement ratio, so that the concrete itself prevents the water from percolating through it, and does not rely solely on the application of a separate coat.
This is significant more than it seems — a tank which relies heavily on the water-tightness of its internal lining is as water-tight as its internal lining, whereas a well-mixed structural concrete tank is water-tight in itself.
3. Internal Lining and Potable Water Suitability
When the tank is used for potable water, the inside surface must be coated or finished with a potable water contact surface (unless the tank is new) and this must be verified, not assumed.
The requirement does not apply to irrigation water, fire suppression water supplies, or process water, although it can be a challenge to change usage after the tank has been cast.
You should check with your water supplier if you intend to use the water for your production, to ensure the right internal finish is applied at the beginning.
4. Building the Concrete Base
A full 5000 gallon tank is a large concentrated load, and requires a base with the capacity to distribute it evenly throughout the entire area of the tank’s footprint.
One of the more frequent reasons for cracking in concrete tanks is an uneven or under-compacted base – any settlement under the tank creates stress points which the tank was not designed for.
The base preparation (compacted sub-base or poured concrete slab) should be sized and weighted to match the actual size and weight of the tank, and not be installed after the tank is delivered.
5. Access, Inlet and Outlet Fittings
A tank should have a suitable access area for inspection and cleaning and have inlet, outlet and overflow connections properly sized and located in relation to the plumbing on site.
These should be designed prior to casting, as adding a new penetration to a completed concrete tank wall will be more difficult and may affect the water-tightness of the tank.
Correct fitment is the first time, saving rework costs after the tank is installed and connected.
6. Above-Ground vs. Underground Installation
Depending on the structural design, a 5000-gallon precast tank can be installed above ground or, in the case of under ground installation, buried below grade — and they require different engineering.
Unlike the greater load that an above-ground tank would be subjected to from the interior water pressure, an underground tank must withstand the external pressure from the soil and groundwater acting inward.
This should be clearly indicated at the beginning as a tank that is above ground will not necessarily be suitable to be buried without making adjustments to its structural capacity.
7. Certification and Manufacturer Quality Control
The precast concrete tank must be sourced from a company that has their production processes and documentation certified.
That is originally due to Dubai Municipality’s Administrative Decision No. 316 of 2012 for precast concrete factories and a Certificate of Conformity issued by Dubai Central Laboratory’s Certification and Quality Control of Products Section (DCLD-CQPS).
In a tank that will be filled with water for years, making sure that this documentation is correct is much more economical than having to correct a failure post installation.
Standards That Tie It Together
The UAE precast concrete water tanks are usually designed to British Standards for structural concrete and water-retaining structures and also include the requirements of the municipality for potable water storage tanks when necessary.
If they cannot explain which standards their tank design meets, and provide certification upon request, that should be considered a red flag before ordering a tank from them.
The Real Challenge is Not Just Matching the Tank to How it Will Be Used
The 5000-gallon tank is a standard, off-the-shelf product, in some respects.
However, the correct specification will greatly depend on the intended use of the tank, potable water, irrigation water, above ground or underground, constant level storage versus repeated full-empty cycles.
Two tanks that have the same specifications on the spec sheet can have vastly different performance characteristics in different applications.
The Bottom Line on Precast Reinforced Concrete Water Tank
A 5000 gallon precast reinforced concrete water tank is a proven and reliable choice for water storage solutions in the UAE – but only when the tank wall design, concrete mix, foundation and fittings are designed specifically for the intended use of the tank.
Get all that information up front and a properly engineered precast tank at this scale will provide a long, trouble-free life of water storage for many years.
If you are considering a 5000-gallon tank for your project, it is beneficial to talk with your intended use and type of installation before you finalize your order.
