The flap valve solution on the Narrow Street Victorian sewer outfall onto Ratcliff beach in Limehouse, London was in need of a replacement. MeasurIT were able to show that a GuvNu valve array would provide the required longterm function as well as being aesthetically pleasing and the valve array was installed in September 2018.

Ratcliff beach in London's East End is where the ESO (Emergency Sewer Overflow) for North London discharges into the Thames river. The brick sewer outfall is 100" or 2.6m in diameter and dates from 1861. It was built during the modernisation of London’s sewer system devised and overseen by Joseph Bazalgette.

As is typical of Victorian sewers constructed during this period, the sewer is egg-shaped and thus not easy to find a check valve solution for it. However, given the wide tidal range of the Thames, it is important to prevent backflow putting strain on the drainage system upstream, while at the same time ensuring that any large flows generated during storms can be released into the Thames.

The existing flap valves have had many modifications made to them over the years, but the sewer was always half full of water. Closer inspection of the sewer revealed evidence of even older flap valve constructions that had obviously failed and/or been removed at some stage over the sewer’s life.