Two first half goals in the space of three minutes from former Waterford player Daryl Kavanagh set St Pat's Athletic on their to qualify for FAI Ford Cup quarter finals at the RSC.
Both sides fielded teams weakened by either suspension or injury but the Premier Division side settled better.
The first chance came on eight minutes when Derek Doyle was sent away on the left by Kavanagh - he crossed to the back post where Anto Murphy headed back into the path of Shane McFaul but he headed high over the bar.
Kavanagh broke the deadlock on 17 minutes when he headed home from close range after Kevin Burns could only parry a powerful header from Evan McMillan.
The ball bobbled around in the six yard box before Kavanagh pounced. And the Carrick on Suir native doubled his side's advantage just three minutes later when he was put through by Anto Murphy and he calmly lifted the ball over the advancing Burns.
Waterford had two glorious chances to reduce the deficit within minutes and both fell to Dwayne Wilson. It was Paul Murphy who provided an excellent cross from the right to the back post and the unmarked Wilson could only head over the bar and seconds later he was put through on goal by Brian Nolan but he could only watch as his curling low effort skimmed outside the right upright.
St Pat's extended their lead just two minutes after the restart when Kenny Browne handled under pressure from Kavanagh and Stephen Bradley fired home from the resultant penalty kick.
Waterford's best effort came when Murphy tested Gary Rogers with a thirty five yard effort on fifty five minutes but the Pat's netminder made an outstanding full length dive to touch the ball away for a corner which was subsequently cleared.
Pat's continued to press forward and a minute later, Derek Pender crossed for Derek Doyle who should have done better but he blasted over.
With the game beyond doubt, Pat's moved into cruise mode and coasted into the next round with Kavanagh being voted Ford Man of the Match.