Derry's Mark Farren celebrates his late winner at Waterford

The game had just gone past the three minutes of time added on when Farren blasted in a superb left-foot volley after Clive Delaney had headed on.

In the first half Farren had seen his penalty saved by United keeper Ben Spicer after a foul on Gary Beckett.

Derry are now level with leaders Shelbourne but have just one game left compared to two for the Shels.

Pat Fenlon's Shelbourne can all but clinch the title by beating Bohemians on Friday night.

Derry are at home to Cork City and a point will make sure of the runners-up place and entry to next season's Uefa Cup.