A second home game under new manager Stephen O'Donnell in which they failed to score further dented St Patrick's Athletic's Europa League qualification hopes as Waterford deservedly won for the second time in Inchicore this season thanks to a double from striker Michael O'Connor.
The result leave St Pat's three points off fourth place with games against Bohemians and Derry City, immediately above them, to come over their three remaining matches.
Chris Forrester made his first league start in three months as St Pat's manager Stephen O'Donnell made for changes from their last outing in earning a creditable draw at Dublin rivals Shamrock Rovers.
With Latvian officials in charge as part of a referee's exchange programme, Blues started on the front foot with winger Walter Figueira cutting in from the left to rifle a drive inches over the crossbar just 23 seconds in.
And though Saints responded, forcing two corners, it was Barry Murphy in the home goal who was the first keeper to see action in batting a stinging Zack Elbouzedi shot out for a corner that brought Waterford the lead on five minutes.
St Pat's didn't deal with the delivery resulting in Dean Clarke clumsily tripping Rob Slevin in the area to concede a penalty which O'Connor confidently despatched, sending Murphy the wrong way.
With Saints at sixes-and-sevens defensively, O'Connor had a shot bravely blocked by Lee Desmond before the St Pat's defender hooked off the line from Kevin Lynch who got in down the left to dink a shot over Murphy.
Switching to a flat back four, and try as they might, St Pat's struggled to impose themselves on the visitors who remained the more threatening side when they got forward.
That was exemplified in first half stoppage time when Murphy had to make his second decent save of game to push away a drive by JJ Lunney from the edge of the area after a surging run through midfield.
O'Donnell made two changes at half-time, bringing in Jake Walker and Glen McAuley for Mikey Drennan and Cian Coleman in an effort to inject some impetus into his side's attack.
But save for Matt Connor tipping a cross from Clarke out for a corner St Pat's continued to labour in creating chances.
And the frailties at the back remained with Blues right-back Sam Bone getting forward to drill a shot narrowly wide before Figueira cleverly chipped onto the roof of Murphy's net.
Connor was only really worked for the first time on 77 minutes when parrying away substitute Ronan Hale's drive.
A minute later O'Connor shot wide of a gaping goal after a counter down the right by Elbouzedi.
But the striker made amends with a towering header from Bone's diagonal cross on 81 minutes to give Murphy no chance for a fine second goal.
Hale was then deprived of a consolation goal for Saints by the save of the game from Connor in stoppage time.