Scrum-half Paul O'Donohoe turned in a man-of-the-match display as Clontarf beat close rivals Blackrock College at Castle Avenue.
Andy Wood's men are now five points clear of second-placed Shannon, thanks to their fifth straight league win.
Darragh Fitzpatrick booted Blackrock ahead but 'Tarf, with their
forwards excelling, snapped back to lead 10-3 at half-time.
Blackrock had David Moore and David Rowan sin-binned and 'Tarf put Martin Dufficy over for a try.
Two five-pointers from Michael Keating and O'Donohoe then put the result beyond doubt.
Clontarf: Tries: Martin Dufficy, Michael Keating, Paul
O'Donohoe; Con: Daragh O'Shea; Pens: Daragh O'Shea 3.
Blackrock College: Try: Royce Burke-Flynn; Pen: Darragh Fitzpatrick.
