Västervik Miljö & Energi
Västervik, Sweden
Area of use 
Flood protection

After a meeting with Västervik Miljö & Energi, the body in charge of the municipality’s water and sewer services, an inspection of the municipality’s overflow system was carried out. The purpose of the inspection was to identify which overflow outlets needed to have a check valve installed as a preventive measure in order to stop backflow into the pipes which can occur, for example, at high water levels. 

One of the overflow outlets that needed to have a check valve installed was a DN1200 concrete pipe leading to an upstream overflow chamber. Two separate pipes lead to the overflow chamber: one for rainwater and one for wastewater with a separating wall in between them. In order to protect the wastewater pipe from overload, wastewater is able to flow over the separating wall and out through the emergency overflow.

However, if water levels are high, this function will make it possible for sea water to flow back through the emergency overflow, thereby entering the wastewater network. This can in turn lead to the municipality having to pump water unnecessarily to the treatment plant which is an expensive process


Installing a check valve in the upstream chamber would not have been an optimal solution considering the design of the chamber. Nor would installing a check valve at the outfall of the pipe have been a good solution since the end of the outlet lies underwater.

Instead, Wapro’s technical salespersons and engineers designed a customized solution together with the client. By removing the crown of the concrete pipe, it was possible to install a WaStop DN1200 with a half flange on the inlet side of the valve by bolting it inside the concrete pipe. With a unique pulsating flow mechanism every time the membrane is opened, the WaStop check valve minimises the risk of anything getting stuck between the membrane and the pipe. The end result is an effectively sealed check valve that will prevent backflow for many years.


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