First half goals from Keith Fahey and Mark Quigley and a late double from Keith Barker were enough to give St Pat's all three points in this action-packed encounter at Richmond Park, writes Mark Cummins.
Fahey got the first on nine minutes with a shot from 25 yards and high into Dean Delaney's net. Quigley then notched number two on 38 minutes from a Joseph Ndo pass.
Sub Robbie Hedderman got Waterford back into it on 50 minutes after being set up by Dave Warren but sub Barker sealed the win on 82 minutes and 86 minutes after great work from Fahey and Keane respectively for either goal.
Pat's took the lead on nine minutes when Fahey got on the end of a Mark Quigley pass and blasted a trademark shot from about 25 yards high in to Dean Delaney's net.
The Blues very nearly got back on level terms just two minutes later but David Breen planted his header over the bar from a good position.
On 16, Quigley set Glen Fitzpatrick up nicely but referee Derek Tomney called play back and awarded a free-kick for a foul on Quigley by Breen.
Delaney then rescued Blues on 18 minutes when he blocked a snap shot from Billy Gibson.
Waterford were playing good football and Vinny Sullivan went close with a header on the 20-minute mark that Barry Ryan blocked at his near post.
The action swung the other way and Joseph Ndo tested Delaney with a cracker from outside the box but the Blues custodian made a great save.
Pat's looked odds to get number two and that they did on 38 minutes.
A Fitzpatrick ball found Ndo deep in the Waterford half and the 21-times capped Cameroon international teed up Quigley who blasted past Delaney from 18 yards.
Blues boss Gareth Cronin made a change at half-time with Robbie Hedderman replacing Daryl Kavanagh and that bore fruit on 50 minutes when Hedderman rose highest in the goalmouth to head Waterford back into the game after a cross from Dave Warren.
Pat's recent injury concerns were compounded on the hour when Quigley limped off, to be replaced by the fit again Gary O'Neill.
On 70, Warren struck a low drive at goal from inside the Pat's box but Ryan got down to make the save.
Seconds later Fitzpatrick wasted a chance to get number three when he shot across the face of goal having eluded Robert Brosnan who slipped in the box.
Barker scored number three on 82 minutes from a Fahey cross on the right and put the gloss on the win with his second and Pat's fourth on 86 after excellent play from Keane.