Derry’s drinking water plant has been restarted after tests on the River Faughan showed raw water quality returning to normal.
The Faughan River supplies 60% of the water used to supply homes and businesses in Derry.
The raw water is treated at Carmoney Water Works in the Waterside before being distributed across the city.
However the plant was shot down as a precautionary measure this week in the wake of the fish kill on the river as a result of a suspected pollution episode in the river.
Thousands of fish are thought to have perished at two sites in Campsie and Claudy over a 20km stretch of the Faughan.
There have been widespread fears that the episode may be linked to discoloured water being experienced by local people in some areas of the city, but NI Water have reassured people that the tap water in the city has always been safe.
A spokeswoman for NI Water said: “NI Water can assure customers the water quality in the Derry area continues to be safe to drink and of the highest quality.
“Following the recent pollution incident in the River Faughan, NI Water took immediate action to protect the water supply in the area which included shutting down the Carmoney Water Treatment Works (WTW) at Eglinton.
“Results from continuous monitoring and sampling show the raw water in the river is once again within normal range and the Carmoney Treatment Works has been restarted.
“NI Water will continue to monitor water quality around the works and continue to liaise with NIEA in relation to their water quality monitoring in the River Faughan.”
The cause of the fish kill was today still being investigated by the Loughs Agency and the Northern Ireland Environment Agency.