Concrete vs Plastic Underground Detention Tanks

Stormwater Detention Tanks can be made from many materials, such as plastic, concrete, fibreglass and steel. Many residential homeowners are choosing to install underground storm water Detention Tanks so they do not have to look at unsightly above ground tanks and to save valuable space on their properties. For underground tanks the main choice of construction materials is between plastic and concrete.

Does Concrete Make Sense Underground?

Concrete is widely regarded as strong and durable, which makes it seem like a sensible choice for underground detention and retention tanks. The Canterbury earthquakes of 2010 and 2011 showed otherwise. Rigid, inflexible underground structures can perform poorly in earthquakes, so does it make sense to install concrete tanks underground as a long-term strategy? Realistically, no.

Why Polyethylene Is the Better Choice

The material of choice for underground Detention or Retention of water, is in fact Polyethylene (or PE for short), the most common plastic because PE, when formed into pipes or tanks is remarkably tough and strong, while maintaining its flexibility, which means it is far more likely to withstand ground movement without failure compared to concrete.

Other Advantages of Polyethylene (PE)

• PE is not porous so will not allow water loss over time.
• PE is much lighter than concrete and therefore easier to handle at installation reducing installation costs.
• PE is 100% recyclable allowing future disposal if required, with minimal impact on the environment.
• PE will not rust, rot, crack or corrode like other materials and therefore has very low maintenance requirements because regular expensive inspections aren’t required.
• PE has a very long life span because it is very inert, making it the choice of material for use with storm water, drinking water and chemicals.

Getting the Volume You Actually Need

APD tanks are made from PE which can easily be worked so Detention Tanks can be fabricated to any desired volume, whereas Detention Tanks made of concrete are restricted to multiples of the volume of the pipes used to form the tank. This is because concrete pipes are pre-formed to certain diameters and lengths and cannot be easily cut to a required length.

For example, if concrete pipes are 1 metre internal diameter and 2.5 metres long, then each pipe can contain a maximum volume of 1.96 cubic metres of water, (1960 Litres) and concrete Detention Tanks made from these pipes, must be multiples of this volume. If a 5 cubic metre Detention Tank is required using concrete, you will require installation of a 5.88 cubic metre tank (1.96 x 3) involving higher initial purchase price and higher installation costs. Contrast that with PE, which can be easily cut and welded to produce a tank of the required volume, minimising the initial purchase price of the tank as well as installation costs.

Call APD today to discuss your requirements .