IT WAS a DIY repair-job gone wrong that has now cost a Sydney man $19,000.

Peter Petrou, 43, was digging outside the house he shares with his parents and children in Randwick on July 31 last year, searching for a leaking pipe that was causing water to gush over his front steps and footpath, when he cut into what he described as a ''fat root'' belonging to an old native brush box tree.

Although the cut did not kill the tree, it had to be removed, the council said, for safety reasons. Mr Petrou was ordered to pay $19,000 by Waverley Local Court for breaching a tree preservation order, thought to be the largest penalty of its kind ever issued in the local government area.

''It's not like I was drilling holes in the night to get a view,'' said Mr Petrou, who used to climb the tree when he was a child.

''It was just a duty-of-care issue. There's kids that walk along that path, and my elderly parents use the front steps … I didn't think one root could kill a tree.''