A specially-designed planter which captures and stores rainwater before slowly releasing it in to sewers has been debuted at a Thames Water sewage treatment works.

The planter at the works in Reading captures the water, or runoff, before it can drain in to the sewer network. This helps reduce the risk of the network being overwhelmed by heavy rainfall during storm events, which can lead to flooding or pollution.

The planter is connected to a pipe from the roof and diverts a proportion of runoff into a small internal tank. When this is full, the excess flow spills over into a larger tank inside the planter, which returns the surplus rainwater back in to the sewer network via a small pipe.

The pipe restricts the flow, reducing the “flash flood” effect of heavy rainfall, and ensures the planter is empty in time for the next storm.

The idea was first developed in 2011 before undergoing several years of testing and redesign. It was made for densely urbanised areas where conventional flood relief schemes aren’t feasible but can be used across the Thames Water region.

The planter is the first of its kind to be installed at the sewage works in Reading. The device is designed to be used in residential gardens, with excess water also captured for future uses such as watering the garden. If it proves successful, Thames Water wants to offer them to customers, especially those in flood-prone areas, for free next year.

Tim Beech, Thames Water’s wastewater systems planner, said:

“Heavy rain can inundate the sewer network.

“These planters provide many benefits. They primarily reduce the impact of storms on our sewer network but also provide water for reuse and a bit of extra green space for planting. On top of this they can serve as an education tool to our customers. If we help a customer think twice about runoff from their new extension, conservatory or front drives then that’s an added bonus.

“It’s one of a series of measures we’re taking to prevent sewers being overwhelmed by flooding. We want to move away from digging up roads, building bigger sewers or upsizing treatment works as it’s far more cost effective to solve at the source – where the rain lands.”

The planter is an example of a sustainable drainage system (SuDS) and is just one of a number of such initiatives being used by Thames Water to safeguard the sewer network.

The company is currently working with stakeholders including local authorities to identify other potential surface water management schemes across the region.

These include removing hard, impermeable surfaces such as concrete and asphalt in areas most at risk of flooding and replacing them with rain gardens and permeable paving.