Twinstore works by using a system of lightweight, helically wound galvanised steel pipes in a range of diameters (0.6m to 3.6m) installed within a lined excavation and backfilled. Instead of being sealed, the pipe joints are designed to pass water into the granular fill.
This balances water freely between the pipes and the backfill contained within an impermeable membrane. Twinstore reduces the overall footprint of the pipe system – a critical factor in many applications – by balancing the void ratio between the tank and the granular fill. The excavation is lined with either an impermeable membrane (GCL or fully welded liner) or a geotextile liner, depending on the site requirements. Water is cleaned as it passes in and out of the tank.