The WaStop Inline Check Valve immediately protects people and properties from flooding caused by backflow. WaStop also protects against odour and pests in the sewer and stormwater systems. Thanks to the product’s use of differential pressure, neither electricity nor human intervention are necessary for continuous operation.

The WaStop is also available with an access chamber, allowing easy access from ground level. The product is then called WaStop Access. 

Click to read more and to see animation - https://wapro.com/en-gb/products/wastop-inline-check-valve