Residents from Whitehead and Islandmagee faced a period of time without being able to turn on their taps in February 1979.
The issue arose after the water supply became contaminated after a diesel spillage.
Government chemists were trying to assess the level of pollution following the accidental spillage of diesel oil into the system.
Since the incident occurred, hundreds of East Antrim homes were warned not to turn on their taps.
The oil was stored at Loughmorne, the main catchment reservoir. It was used to fuel the generators which drove the pumps.
A spokesperson from the Department of the Environment said: “A fair amount of diesel was spilled and this entered the treatment system, which in turn contaminated the supply. The oil is pretty obnoxious both to taste and smell and we would advise householders not to use their taps.”
There were four stationary water tankers set up in Whitehead and Islandmagee, as well as a roving vehicle delivering water to the elderly.
The DOE spokesman said that the situation had improved in the days since the spill.