Draining the reservoir was one of two options being considered by the company, but it will now refurbish the site instead, which is popular with locals and is used by the local fishing club.
UU launched a study last month into the work needed at the site and to determine the cost of needed on the embankment and for essential equipment to allow water to be drawn from the reservoir in the event of an emergency or planned event.
Despite being withdrawn from service 40 years ago, UU has continued to maintain the site in line with regulations under the 1975 Reservoir Act, which states that water companies have a legal obligation to either carry out all necessary remedial work on a reservoir or to drain it and return it to its natural state.
UU now plans to reduce water levels so that it can start making the essential repairs.
A version of this story first appeared on wwtonline.