Category Archives: Harvest Rain Water

Are You Flooding? Get A Detention Tank!

If you are living in an area that is constantly being developed or re-developed, chances are you deal with street floods whenever there’s a storm or heavy rainfall. The reason for this is that urban development increases “hard surface” which doesn’t absorb water, unlike soil and grass. Examples of hard surfaces are concrete paths, roofs and paved areas.

Intense rainfall dumps large amounts of water on your property. And since stormwater is no longer being absorbed into the land, there is increased run-off into local stormwater systems. As more dwellings are built, the public infrastructure becomes considerably undersized.

A good solution to ease the pressure on existing infrastructure is installing detention tanks. In fact, this is now a mandatory requirement for new homes as well as extensions. Having a detention tank plumbed into your existing drainage system is also encouraged as it makes stormwater run-off more manageable.

What is a detention tank?

A detention tank stores water collected from your hard surfaces during a rainfall event, then releases the water into the public drains at a slow, controlled rate. The slow release of the stormwater reduces peak stormwater flows and, in turn, reduces the impact on stormwater systems as well as the chance of flooding.

Detention tanks are different from rainwater retention tanks. A retention tank is a normal water tank which simply harvests rainwater and “retains” it for domestic use. Most retention tanks can only hold so much water. In case of intense rainfall, they can quickly fill up and the water overflows into the local drains in an uncontrolled manner.

On the other hand, a detention tank is intended to remain empty to make space for stormwater runoff during periods of rainfall.

It should also be noted that stormwater is different from rainwater.

Rainwater refers to rain that falls on roofs, while stormwater refers to rain that falls on hardstand surfaces other than roofs. The distinction lies in the quality of the water. Research has proven that although rainwater harvested from a roof may contain dust or debris, the debris is likely to be organic and the quality of the water makes it excellent for use in the household. Meanwhile, stormwater may have potential contaminants such as oil drops, pet droppings and rubbish.

Detention tanks may be installed above or underground.

Detention tank solutions

A detention tank is designed to empty the required amount of water at the required rate.

How big your detention tank should be depends on the specifications required by your local council. The council will also specify the size of the orifice and the flow rate of water from your detention tank. In most cases, a certain percentage of your roof or ground area will be specified for use in harvesting stormwater.

Aside from the specified size and capacity, these are the things to consider when selecting a detention tank for your property:

  • Space and budget considerations
  • Aesthetics
  • Ease of installation
  • Maintenance

If you need help choosing the right type of detention tank, contact us on 0800 768 284 and we’ll talk you through the specification and building process.

All About Detention tanks

You maybe have been browsing our website and no doubt came across our detention tank range. There are tanks in all shapes and sizes. But what are these tanks actually for?

Detention tanks, which are sometimes called retention tanks (though this is incorrect), are generally used when storm water system in not adequate enough to deal with the job of extracting water. The detention tanks works to slow down the rain that comes off your roofs and goes into the stormwater system, to prevent overflowing. This is generally an issue in older areas where a lot of new houses are being built and a lot of strain is being put on the stormwater system. Where this is an issue, councils often require the use of detention tanks.

What happens if you have a retention tank is instead of the water flow straight into the stormwater, it comes off the roof and other areas and into the detention tank, then drains slowing through the orifice outlet into the stormwater system. The tank and orifice will be specified to drain at a certain rate, depending on what the stormwater can handle. This can take hours depending on the flow rate. The area your building is in will have specific requirements for this.

Detention tanks can be stand alone units, but often times there are combined with a retention tank. The retention tank stores water for when you need it, in contrast to the detention tank. So how this works will be if you use a 3000 litre tank, the bottom 2000 litres will be used to store your water, and the top 1000 litres for detention.

So what do you need to look for when buying a detention tank? The first thing you’ll need to look at are the council requirements in your area for water flow. You need a tank that will meet these requirements, which will determine the size your orifice you need to select. If you are going to going to be getting a combination retention tank, then you also need to take into account how much water you need for storage. You also have the choice of above ground or below ground.

We have a wide range of detention tanks on our website in all kinds of configurations, sizes and shapes. Have a look through our range and contact us if you need assistance selecting a tank for your home!




Can an underground tank be of plastic?

Concrete water tanks were once the norm in New Zealand but as the future progresses more and more people are starting to opt to go for plastic water tanks surprisingly.  Why is this?  Are there benefits to plastic over concrete? Many questions arise over this subject so let’s look into it.underground_water_tank

One of the main problems with a concrete water tank is they can be damaged surprisingly easily, for example, many tanks end up cracking after an earthquake, or if the ground moves too much from a slip etc.  In New Zealand these sorts of events are quite common, common enough that people are now looking to alternate options such as plastic which doesn’t have the same problems as concrete.  Plastic tanks wont rust, rot, crack or corrode like other materials and are easier to install.  Plastic tanks won’t get damaged by an earthquake and a generally cheaper aswell. Another advantage is plastic can be moulded into a variety of sizes and shapes to fit your home. Some ask what about a fire?  If a fire is burning hot enough to melt an underground plastic tank it would be hot enough to explode a concrete tank or melt a steel tank aswell.  Being buried adds protection to a tank as well as giving more space in your environment.

Rotational plastics storage tanks are

  • Extra strong, one piece virtually stress free moulding
  • UV stabilised to maximise outdoor life
  • Full range of colours available
  • Hygienic food grade Polyethylene resistant to most chemicals
  • Easy to install

Checkout our collection of underground water tanks as follows:

Tank 1000L with 600mm Riser and 300mm Sump.  This has a length of 1400mm, width 1200mm, height 900mm (approx.)

Tank 2000L with 600mm Riser and 300mm Sump.  This has a length of 2800mm, width 1200mm, height 900mm (approx.)

Tank 3000L with 600mm Riser and 300mm Sump.  This has a length of 4200mm, width 1200mm, height 900mm (approx.)

Tank 4000L with 600mm Riser and 300mm Sump.  This has a length of 5600mm, width 1200mm, height 900mm (approx.)

Tank 5000L with 600mm Riser and 300mm Sump.  This has a length of 7000mm, width 1200mm, height 900mm (approx.)

Tank 375L. This has a length of 1200mm, width 700mm, height 750mm (approx.)

Tank 500L. This has a length of 1190mm, width 680mm, height 980mm (approx.)

Call us for a quote or advice.

Retention/Detention tanks in demand

What are retention/detention tanks?

Simply put a detention tank holds the stormwater overflow and slowly releases it into the public system while a retention tanks stores this water and you are able to use it. You can also get a dual purpose tank that does both. The top of the tank is released into the public system and it holds what is left once it reaches a certain level.


Why the call for them?

Auckland as we are all aware is growing fast and strong.  With all the new houses being built and all the new people coming to live in Auckland there is a worry the public system will be overloaded.  So the council is asking home owners to have these tanks installed to help.

Why choose Rotational plastic tanks?

Rotational tanks are the best option as their height is only 1 metre.  Also if site conditions are struggling for falls this is the only tank that will work.  Our tanks can be manufactured to any size as we can add on 500L sections. They are capable of above ground or below ground applications.  They can be used for industrial, agricultural or residential applications.  They are made for easy maintenance. Its key features are:

  • Tanks are pre-assembled and ready to install
  • Have a unique double filter system, and easily removable catch pit filter
  • Modular 1000L increments
  • Ideal for hard to access locations
  • No special bridge requirements
  • Moulded-in inlet and outlet pipe options
  • Multiple inlet and outlet options

Our tank standards are:

  • Designed and engineered to AS/NZS requirements
  • Complies with load testing for light and medium vehicular loading
  • Plastic construction and moulding complies with AS/NZS 4766.2006 specifically for polyethylene storage tanks for water and chemicals

Other information

We suggest having leaf deflectors installed on downpipes to prevent unnecessary buildup of debris in the tanks.  The removable filter bucket is designed to reduce maintenance costs by eliminating the need for regular pumping of silt and debris.  To ensure good operation the tanks should be regularly inspected and cleaned. The envirogental detention tank system has a double filter system, the first is built for large debris at the inlet point so it can easily be removed and cleaned and an easy clean sump is incorporated into the base below the inspection riser to further collect debris.

Why Harvest Rain Water?

You may have heard of harvesting rain water before, but what are the benefits? Is it really worth the investment? And what actually is it?

harvest_rain_waterHarvesting rain water is the accumulation of rain water for later use on the property or site where it is collected. Common uses of rain water are for watering the garden, feeding livestock, indoor heating, and use in the home (with proper treatment).

One big positive of rain harvesting is it provides an independent water supply for the property, which is particularly useful in rural areas or regions with water restrictions. Harvesting systems are also very easy to install, requiring little specialised skill and are often low cost.

Where do you store the harvested water? Water tanks are the solution for storing your harvested water. There are a range of different tanks to choose from, such as above ground or below ground. The choice will depend on your application.

See our range of rain water harvest tanks here.