Graham Burke scored twice as Shamrock Rovers survived an early scare at the RSC to see off struggling Waterford and move three points clear at the top of the table.
Enthused by manager Marc Bircham to use last week's shock victory at Dundalk as a springboard to mount a survival bid, Waterford soared ahead from their first attack on five minutes.
When Eric Molloy was left alone on the left to receive a pass, he opted to cut in and shoot from the edge of the box.
His ambition paid off as the stinging effort deflected off Sean Hoare and whipped past the wrong-footed Alan Mannus for his first goal of the season.
In response, Burke dragged his shot wide and Liam Scales tested Brian Murphy for the first time with a shot he gathered.
Then came the contentious turning point on 14 minutes.
When Sean Gannon's cross struck the arm of Jamie Mascoll, linesman Darragh Keegan did not flag but referee Adriano Reale, standing behind the defender, blew for handball and pointed to the spot.
Burke stepped up to drill his penalty into the bottom left corner, despite Murphy going the right way and getting a hand to the ball.
Much to the approval of the 200 fans in the RSC for the first time this season, chances for Prince Mutswunguma and Aaron Greene were swapped at either end.
But the volume grew loudest approaching the break when Reale failed to issue even a booking to Hoops midfielder Chris McCann for leaving Mutswunguma writhing in agony.
Rovers inflicted pain of a different variety on the Blues with a second-half onslaught.
Barely three minutes had elapsed when Gaffney pounced to a Cameron Evans error on the edge of his box. The striker needed just one touch to control the ball and unleash a crisp drive beyond Murphy and in off the post.
Rovers continued to run the youthful Waterford defence ragged, leading to Burke's second on the hour.
After Greene beat Jack Stafford in a foot race on the right side, he squared for the playmaker to sweep home his seventh of the season from close range.
The visitors’ attackers were by that stage rampant and, with 20 minutes remaining, Greene exchanged passes with Gaffney before leaving Murphy rooted to the spot with his fine finish.
Waterford: B Murphy; D Power, C Evans (L Kervick 70), J Mascoll, J Stafford, E Molloy; J Martin, N O’Keefe, S Griffin, A O’Reilly (K Mashigo 77); P Mutswunguma (T Sobolwale 70).
Shamrock Rovers: A Mannus; S Gannon, R Lopes, S Hoare, L Grace (D Nugent 70), L Scales; C McCann (G O’Neill 66), D Mandroiu, G Burke (R Finn 66); R Gaffney (A Emakhu 70), A Greene (D Williams 70).
Referee: Adriano Reale (Kildare)