The emergency drawdown rate (the rate at which the water level in the reservoir can be reduced) was about 0.25 metres/day. Inspections in 2005-07 identified that this was inadequate, and proposed that the drawdown should be 0.75 m/d as defined in the provisions of the "Reservoirs Act 1975". This was achieved by installing twin 1.6 m diameter siphon pipes over the embankment. The valves controlling the outflow are 13 m high and have a flow capacity of 13 m3/s. The discharge pipes are 250 m long and discharge into the Laleham Aqueduct, returning water to the Thames.  