22No. 900mm Tideflex Valves at Tees Barrage Nov 27, 2017 Twenty-two 900mm Tideflex check valves have been operating problem-free on the Tees Barrage Fish Pass since 1995. This is another example of how Tideflex duckbill valves can be used to solve complex o... River Outfalls Sites England backflow prevention eel friendly fish friendly fish pass tidal outfall tideflex valve Read more