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The Stormsaver Active Attenuation system combines Attenuation and Rainwater Harvesting in one system which can be either an above or below ground arrangement. The Stormsaver Active Attenuation system counts towards 100% of attenuation volumes on-site at the same time as Harvesting Rainwater.

This is made possible by connecting your Rainwater Harvesting tank and attenuation system via pipework allowing stored rainwater to be drained down before a storm event. Your Rainwater Harvesting System becomes part of your attenuation capacity, meaning you can reduce the number of attenuation crates/tanks used.

Half of the attenuation tank collects surface water run-off and acts just as a regular attenuation tank, while the other half collects roof run-off and stores it within the Rainwater Harvesting System. The Active Attenuation technology is directly linked to a highly accurate, short to medium term Met Office Rain Prediction System. When rainfall is predicted, Stormsaver’s telemetry recognises the anticipated rainfall event.

The system measures the water levels with the integrated level sensor in the storage tank, then controls water levels within the attenuation and Rainwater Harvesting tanks, by controlling a low level valve or attenuation pumps. This is linked to the Rainfall Prediction algorithm housed in the Stormsaver Active Attenuation control panel. The water is then lowered to a safe level so when the rainfall event arrives the necessary attenuation capacity is available within the tank, while also allowing Rainwater Harvesting capacity to service the buildings water demand.

The system has a built-in fail safe so that the total attenuation capacity is available for all events that the system is designed for. Utilising mandatory flood protection infrastructure in this way the Stormsaver system provides all new commercial buildings with a source of valuable recycled rainwater without the need for additional, expensive infrastructure.


Active Attenuation is one of the best ways to manage stormwater.

Not only does Active Attenuation provide a non-potable water supply through recycled rainwater, but it can also reduce stormwater discharge rates by reusing rainwater stored in the attenuation capacity.

Think of the technology as a 2-in-1!

Why this is important…

  • A water deficit of 5 billion litres every day by 2050, according to the Environment Agency.
  • Many areas in the Southeast are considered seriously water stressed, hindering further development.
  • UK Government targets to reduce non-household use of public water supplies by 9% by 2038.
  • An ageing combined sewer network transports stormwater and foul water, causing untreated sewage to overflow into waterways during heavy storms.
  • The natural drainage cycle is being increasingly disrupted by ongoing construction, preventing the natural infiltration of stormwater.

Active Attenuation produces a non-potable water supply. Non-potable water supplies can be used for…

  • Toilet flushing
  • Vehicle washing
  • Manufacturing processes
  • Irrigation
  • Laundry
  • Cooling

Active Attenuation is suited for high water-using properties looking to improve water efficiency standards, including…

  • Manufacturing sites
  • Distribution centres
  • Mixed-use developments
  • Leisure facilities
  • Supermarkets
  • Hospitals
  • Stadiums
  • Offices

Our System Types 

Active Attenuation can be achieved in many ways. The type of system will depend on your project requirements, including water demand needs, and attenuation requirements.

Our team of experts is on hand to propose the best system type for your water-saving requirements. See our solutions below.

 a diagram of a combined rainwater harvesting and attenuation system reusing rainwater within a commercial building

Below Ground

  • A common method of achieving attenuation.
  • Available in crates, tanks, and tunnels.
  • Achieve optimal water quality by segregating roof and surface water into two capacities, connected via a non-return valve.
  • Includes a small rainwater tank, connected to the attenuation capacity, for filtration, pumping, and maintenance requirements.
  • Attenuation capacity should be positioned slightly higher for efficient drainage into the rainwater tank.
  • Can incorporate a maintenance control box within the crates for cleaning.

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 a diagram of a combined rainwater harvesting and attenuation system in an above ground format.

Above Ground

  • Ideal for urban areas with limited below-ground space.
  • Sectional storage tanks are ideal for installation in basements and can be utilised for both rainwater harvesting and attenuation.
  • Compatible with concrete tanks where there is sufficient space for a pre-tank filter and maintenance access.
  • Where drainage is located at a lower level than the attenuation tank, Active Attenuation can control booster sets for pumping excess stormwater.
  • Can be used as a retrofit solution for where flooding is a concern.

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 A rainwater harvesting system recycling rainwater from a blue roof for non-potable use within a building

Blue Roofs

  • Blue or blue-green roofs are ideal for cities.
  • Save space on the ground by utilising the roof space for attenuation.
  • Contribute to biodiversity net gain, higher water efficiency, and reduced flooding.
  • Reuse rainwater from the blue roof system for a non-potable water supply.
  • Reduce pumping requirements by taking advantage of a gravity feed.
  • Active Attenuation controls the transportation of the stormwater, either to the drain or to the rainwater harvesting system for reuse.
  • Reduce the size of the internal rainwater storage tank.

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 a diagram of a combined rainwater harvesting, greywater recycling and active attenuation system

Combined Systems

  • Ideal for large developments in densely populated areas.
  • Integrates Active Attenuation, rainwater harvesting, and greywater recycling in one smart system.
  • Combined systems offer a consistent supply of recycled water, not dependent on the weather.
  • Meet a larger volume of your non-potable water demands through reusing both rainwater and greywater.
  • Tailored to your specifications.
  • Involve us early in the design process for correct sizing, filtration, and maintenance considerations.

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Technical Features

IOT Monitoring: Ease of monitoring of stored water levels and system health through a real-time customer portal.

Smart Weather Prediction: Autonomous monitoring of weather patterns 72 hours ahead, ensuring 100% of capacity is always available.

Safe-to-fail Operation: Includes battery backup and will default to a standard attenuation system in a failure scenario.

PLC Controls: Smart system with easy-to-replace components, minimising downtime compared to more common PCB controllers.

BMS Connectivity: Custom-designed to easily monitor storage levels, water consumption, faults, salinity levels, and temperature.

Mains Water Backup: Always prioritises rainwater but will automatically switch to mains water when necessary for a steady supply.

Mains Water Protection: Prevents mains water wastage with automatic shutoff valves and alerts, avoiding high water bills in valve failure scenarios.

Further Information

Maintenance – make it easy! The Active Attenuation System will be in operation for decades; therefore, it is important to ensure the arrangement specified is easy to maintain.

Cleaning of the attenuation crates – Stormsaver systems can be supplied with a maintenance control box for easy cleaning of the attenuation crates.

Collection surfaces – for the best water quality, only reuse rainwater from the roof area. This will mean separating the roof and hardstanding attenuation capacities and connecting them via a non-return valve.

Maintenance access – Stormsaver systems take advantage of a small rainwater storage tank which is attached to the attenuation capacity. Essentially, this tank acts as a pumping, filtration, and valve chamber. This arrangement ensures ease of cleaning and maintenance.

Why Choose Stormsaver?

Our Added Value Options

Looking for additional filtration, UV disinfection, or installation services? Our added value options give you access to best-practice approaches. Learn more here. 

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