A statutory inspection of Burnhope Reservoir completed under Section 10(3) of the Reservoirs Act 1975 (HMG, 1975) noted that the 30-inch washout valve at the outlet tunnel portal had not been tested for some time. A Measure in the Interests of Safety (MITIOS) was to simply open and close the 30-inch washout valve over its full range to prove its operability. However, the washout valve is located on the outlet of the 40″ supply main, which provides both a raw water supply to the Water Treatment Works (WTW) and can also be used for emergency drawdown. Should the washout valve fail, the consequence would be a loss of pressure to the WTW, which would shut down. To maintain deployable output throughout the testing of the washout, its subsequent replacement and installation of a new free discharge control valve, a new 600 mm cross-connection pipeline was installed between the independent 40-inch supply/emergency drawdown main and 30-inch scour main. This cross-connection pipeline then removed the risk of interrupting the water supply and permitted the washout to be tested and subsequently replaced whilst also providing a resilient water network and much improved control of the 40″ supply main drawdown asset.