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underground storage taNks

RotoTankTM is a manufacturer of underground storage tanks, water tanks, chemical tanks, transport tanks, septic tanks and silos. We are a national brand with branches around the country. We sell directly to the public and deliver for free.







Underground Tank Product Gallery


Underground Tank Technical Download List

300 L UN300 17kg 840mm 770mm n/a n/a 430mm Download
600 L UN600 30kg 1040mm 900mm n/a n/a 450mm Download
1000 L UN1000 40kg 1210mm 1100mm n/a n/a 450mm Download
1750 L UN1750 55kg 1430mm 1300mm n/a n/a 450mm Download
2500 L UN2500 110kg 1780mm 1440mm n/a n/a 450mm Download
5000 L UN5000 250kg n/a 1480mm 2200mm 2380mm 450mm Download
6000 L UN6000 275kg 2120mm 1885mm n/a n/a 450mm Download
8000 L UN8000 440kg n/a 1830mm 1830mm 3800mm 450mm Download
**12500 L UN12500 500kg 2800mm 2700mm n/a n/a 450mm Download
12500 L UN12500 500kg 2800mm 2120mm n/a n/a 450mm Download

Modular Underground Tanks - Dual & Multi Chambers

2500 L 2500L
Dual Chamber
110kg n/a 1400mm 1760mm 1760mm 450mm x 2 Download
4300 L 4300L
Multi Chamber
175kg n/a 1400mm 1760mm 2650mm 450mm x 3 Download
6100 L 6100L
Multi Chamber
240kg n/a 1400mm 1760mm 3540mm 450mm x 4 Download
7900 L 7900L
Multi Chamber
305kg n/a 1400mm 1760mm 4430mm 450mm x 5 Download

** 12500 L - 12500S - This Tank is only Available in the Cape Region

Rainwater Storage Tank Recommendations

Some homeowners and facility managers prefer to harvest rainwater and store it underground as opposed to utilising vertical tanks above ground. It might be an aesthetical requirement or as a consequence of limited space. 

Underground storage tanks from RotoTank™ can be used for storage of municipal water, rainwater harvesting, grey water, conservancy water waste or any other liquid which may be stored underground legally. It is critical that installation instructions be strictly followed.

The Tanks are fitted with a screw-on threaded 450 mm manhole lid included for easy access and inspection. It can be installed in series for large installations.

Storage Tanks have thicker and stronger walls to prevent it from collapsing. The materials are food safe (FDA approved plastic for potable water).

Storage Tank Recommendations

Benefits of an Underground Plastic Tank

The following considerations may assist a prospective customer in his / her decision to install an underground storage tank as opposed to an above ground rainwater harvesting tank. Some of these considerations are:

  1. Preservation of open spaces. It is true that rainwater tanks by nature of their design takes up a lot of space. The rounded shape does not normally fit in easily in confined domestic yards and often urban areas have limited space for such tanks. An underground tank will provide a reasonable amount of water storage space while being out of sight of the occupant.
  2. Underground tanks are not exposed to ultraviolet radiation of sunlight. This means that an underground plastic tank, if installed correctly will last a very long time.

3. RotoTank™ underground storage tanks are equipped with child safe manholes and it may be covered completely with a decorative manhole cover if needed.

4. Because the tank is completely sealed and buried it cannot be infested with any contaminants which may often be found in vertical tanks.

5. RotoTank™ has a large variety of sizes and can provide its customer with any size of tank ranging from 300lt up to 12500lt for underground use.

6. A plastic underground tank is less costly to install than brick-built tanks. It is unlikely ever to leak if installed correctly, while mortar and brick tanks does crack over time.

Installing an Underground Storage Tank

Installing an underground water storage tank is simple when you have the right tools for the job. In this article, you will learn a simple 6-step installation method that includes an explanation of the recommended materials and machinery to be used. Using the correct backfill material to bury a polyethylene tank is particularly important as it will lengthen the life of the tank significantly. Because these tanks are getting buried, you must also be extra cautious about where you are installing them. The geographical  elements of certain areas may require you to consider extra cautionary steps.

Backfill Material Instructions:

Using the correct backfill material will minimize the possibility of the tank collapsing. This is an extremely critical part of installation and must be followed. A one-to-six ration of river and cement mix is required to encapsulate the tank. If the geographical area is prone to high water table levels during the raining season this ratio may be increased. When mixed care should be taken not to ad water and make a wet mix, it should be a dry mix for filling the bottom of the hole and around the tank. It is important that all material must be free of sharp objects that could cause damage to the tank.

7-Step Installation Guide for Underground Water Storage Tanks:
  1. Excavate – Measure the length and width of the tank. Add at least 250mm on both ends and sides of the tank and mark those dimensions on the ground. Excavate to a depth that will provide a minimum of 200mm and a maximum of 350mm of cover over the top of the tank. Topsoil may be placed over the filling after the filling have been lightly compacted and hardened.
  2. Prepare Base – Remove any roots and rake the bed flat. The preferred tank bedding material is the filling material described above. After measuring and filling in the base layer of 250mm of filling, lightly compact and level before setting the tank. Ensure there are NO SHARP OBJECTS mixed filling. This could puncture the tank without you knowing.
  3. Set the Tank – Place the tank in the middle of the hole. Begin pushing the tank back and forth to allow the base filling to fill in the ribs along the bottom of the tank. If you are lowering the tank in the hole using a crane or excavator, level the tank before removing the straps in case further excavation is needed.
  4. Install Connections – Install bulkhead fittings in tank. You MUST plumb with a flexible hose directly from the bulkhead fitting. This prevents any movement that could break the fitting and put extra stress on the tank. Extra fittings that are installed in this tank are the responsibility of the owner. Underground tanks must be vented to prevent them sucking in when water is being pumped out.
  5. Add Risers – Remove lid and gasket that is supplied with the tank. A RotoTank™ riser varying from 300mm to 900mm may be installed on top of the tank to secure access to the tank. More risers may be added to accommodate the depth of the hole. Add lid and gasket to the top riser installed.
  6. Backfill – Begin filling in the space around the tank with the recommended filling material and compact in layers of 200-300mm. Make sure all gaps under the tank are completely filled. ALWAYS COMPACT EVENLY AROUND THE ENTIRE TANK. Make sure to compact backfill under pipes. Carry on layering the filling until a layer of at least 200mm is lightly compacted over the tank.
  7. Finishing off the installation – Once the tank is installed in the ‘sand/cement powder mix’ it can be finished off by adding topsoil over the tank. The vent or risers should be properly secured.

    Quick Summary:

    Now you have a basic idea of how to install an underground water storage system, you’re set to go! Regular checks of an under-ground tank is recommended to ensure nothing out of the ordinary has happened. If you are using your underground tank for drinking or potable water, you should also make an effort to monitor the water quality to be sure no debris has entered through the tank lid.

Install your Own Underground Storage Tank
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