Read more about the importance of filtration in a rainwater harvesting system

Read more about the water quaity from of our rainwater harvesting systems.

Not sure which tank you need?
Use our calculator to find out.

Learn about looking after a rainwater harvesting system.

Wisy Sigma logo
Sigma - The Elegant, Energy-efficient Solution
Fully WRAS Approved Rainwater Control Unit
Use Me For
Easy-Rain tank with Sigma rainwater system
  • Class-leading low energy consumption (as low as £3 per house per year)
  • Easy to install
  • No mains back up to main storage tank
  • WRAS Approved
  • Simple maintenance
  • Quiet operation
  • Highly suited to retro-fit systems
  • Shallow excavation
Sigma WRAS Approved rainwater unit
Energy saving rainwater system
Energy Saving
BS8518 Compliant Rainwater systems
BS8518 Compliant
Easy to clean filter
Easy to Clean
0.2mm Fine Mesh Filter
0.28mm Mesh Filter

The WISY® Sigma rainwater unit is extremely versatile and is suitable for most domestic installations, both for new properties and also to retro-fit into an existing one. It can be used with underground or above ground tanks and is very simple to install.

Mains water back up is achieved via a small break tank built into the Sigma unit. This mini break tank accepts the mains water supply and provides the required statutory air gap to prevent the cross contamination of mains water supply. As of April 2016, all Sigma units are WRAS Approved.

Having the mains water supply go to the pumping unit rather than to the main storage tank has certain advantages, and saves on having to provide ‘top-up’ to the main tank.The system can be switched to run from the mains supply only should you wish and is extremely quiet in operation.

The Sigma unit is built from the best possible components and with the quality engineering that is typical of WISY® AG.

Combined with one of our Easy-Rain shallow-dig tanks, we offer a simple solution for most domestic properties. And being WRAS Approved means installers and householders have peace of mind.

Read more about the importance of filtration in a rainwater harvesting system

Read more about the water quaity from of our rainwater harvesting systems.

Not sure which tank you need?
Use our calculator to find out.

Learn about looking after a rainwater harvesting system.