The Reservoir (Safety Provisions) Act 1930 required reservoirs to be inspected, and the Commissioners asked E. C. Oakes, the water engineer from Preston Corporation to carry out their assessment in 1933. He reported that there was some subsidence, there were leaks in the clay core and at least one of the outlet pipes through the dam was broken. Repairs were carried out, with all of the outlet pipes being renewed, and as the valve in the valve house was no longer operational, a new valve was installed on the upstream side of the dam, with control rods running up the stone cladding of the dam to a control wheel on its crest.