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How to Choose Between Retention and Detention Tank

How to Choose Between Retention and Detention Tank

Retention and Detention Tanks may sound similar but they perform different functions. One is for long-term use while the other is for short-term use. Both tanks are used to collect rainwater and stormwater.

The major difference between the two is this: retention tanks are built to store water for later use while detention tanks drains water in a short while after it is collected. So what is a retention tank? And what is a detention tank? Read on to find out.

What Is a Water Retention Tank?

What Is a Water Retention Tank

A Water retention tank is designed to capture and store both rainwater and stormwater and retain the water for future use. You can use the harvested rainwater for:

  • Watering plants
  • Flushing toilets
  • Filling swimming pool
  • Washing cars and driveways
  • Washing clothes
  • Drinking (water needs treatment and must be well-maintained)

How a Water Retention Tank Works

The water retention tank collects water from rain or storms and stores it until such time that you’re ready to use it instead of merely draining it. This means you can keep the water for use in the near future. The water retention tank comes in various sizes so you can customize depending on your needs.

What Is a Water Detention Tank?

The water detention tank also captures water from rain or storms but it detains water for a limited time only. It is designed to drain water and built to stay empty, except during rainstorms and for a short time after that.
What Is a Water Detention Tank

How a Water Detention Tank Works

The water detention tank helps lower storm waterflows from small buildings and houses. It limits the flow of storms with short duration by storing water temporarily and releasing it through a restricted throttle, although at a risk of increased flow duration.

Water detention tanks have a large inlet pipe and a smaller outlet, preventing sudden surges of water runoff by controlling the flow. Water detention tanks also prevent flooding.

At Rotational Plastics NZ Ltd, we have developed detention tank as a multi-use, underground tank, either as a detention tank (slow release of water into storm water drain or other runoff), retention tank (used for reuse) or alternatively a combination of both.

In a recent survey in Sydney, 90% of all detention tanks were blocked or had been disabled (the office plate has been removed to eliminate blockages). Our tank is designed to alleviate these problems with a double filter system – one for large debris at the inlet point that can be removed and cleaned in a similar fashion to that of a swimming pool filter or pond filter and a secondary filter box on by the outlet of the tank to catch smaller debris.


Whether you’re looking for short-term or long-term water storage you can go no wrong with Rotational Plastics’ retention tanks and detention tanks. Our tanks are sturdy and built to last through many rainstorms. Choose from a wide range of products to suit your needs.

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