Attenuation Tanks

GRP Preformed Tanks

These GRP preformed tanks are made off site ready for installation in a concrete surround. As well as Attenuation Tanks, Rainwater Harvesting Tanks can be used as part of a SUDS solution, see the Water Recycling section in our Commercial, Public & Industrial Buildings Specifier.


  • Storage applications
  • Trafficked or non trafficked applications
  • Large or small storage capacity - an unlimited size can be achieved by interconnecting tanks
  • Practically all ground conditions, even high water tables
  • Accepted for adoption
  • Where access for inspection is required

Features & Benefits

  • Easy and quick to install, no complicated on site assembly
  • Trafficked or non trafficked applications
  • Deep excavation systems to 5m
  • Suitable for all ground conditions
  • BBA certified tanks available
  • Available in 2 in line and 1 off line systems
  • Suitable for flushing and jetting maintenance
  • Single tanks up to 275,000L - can be interconnected to create larger storage volumes

GRP Attenuation Tanks Range

In-Line Attenuation Tanks

In-line systems are designed to allow water to back up through the tank, and drain by gravity through the separate GRP chamber, housing a vortex flow regulator, or within the balancing tank itself.

V1: Orifice Tank Systems

  • Based on pressure, with flow being regulated through holes (varying sizes) in an orifice plate.
  • Simple and inexpensive.

V2: Vortex Control Tank Systems

  • Based on creating a rotating flow around an opening at high speed to limit outflow.
  • Works in a similar way to a bath: a vortex reduces the flow even though there is water drain.

Off-Line Attenuation Tanks

Off-line attenuation tanks have a flow regulator in a separate chamber, and so allows water to build up and even overspill into storage tanks to cope with even the worst of situations.

V3: Off-Line System

  • The storage tank is emptied using in-built pumps which are automatically activated after a storm has passed.
  • System provides a shallow inlet to outlet ratio and so can withstand larger flows of stormwater.
  • Patent pending.