Pat’s opened the scoring through Conan Byrne after his shot took a deflection off Limerick defender Robbie Williams three minutes before half-time, giving the hosts a 1-0 lead heading into the break.
Their second finally arrived on 77 minutes with Christy Fagan heading home after a dominant second-half display from Liam Buckley’s side.
The Saints had a penalty shout midway through the opening half but referee Ben Connolly waved play on before Christy Fagan hit the bar seconds later.
The visitors took the game to their top-flight opponents to begin with and enjoyed the majority of the early midfield possession.
Limerick had the first real chance of the match after four minutes, but Lee Lynch’s shot from outside the Pat’s box flew over Brendan Clarke’s crossbar.
The previously undefeated visitors, enjoying a runaway lead at the top of the First Division, certainly did not look in any way out of their depth against a Saints side languishing in the Premier Division’s midtable, but they failed to take advantage of some good possession before the tide eventually turned.
Martin Russell’s men continued to press midway through the half, yet they struggled to create chances within Lynch again shooting wide on 24 minutes.
Pat’s penalty shout came two minutes later when Jamie McGrath was taken down by Limerick centre-half Robbie Williams.
Dublin official Connolly opted against awarding a spot-kick, but McGrath admirably rose straight to his feet, centring the ball for Fagan, whose shot hit the bar before Limerick cleared it for a corner.
The hosts had been slightly sloppy up to this point, but they were gradually wrestling control of the game.
The opener came on 42 minutes as Keith Treacy pinged a ball towards Byrne, who worked his way into the Limerick box before letting off a shot that took deflection off Williams past keeper Freddy Hall.
Pat’s nearly went two up soon afterwards, but Ger O’Brien’s curling effort from outside the box one minute into injury-time was punched over by Hall, leaving Pat’s one up at half-time.
Buckley’s Saints again come close to doubling their lead seconds after the break as Fagan’s shot was blocked after good work and a fine cross from Ian Bermingham on the left wing, while Byrne’s blast from outside the box was touched over by Hall five minutes later. It was pretty much all Pat’s at this stage with Fagan and Doyle creating regular openings in the visitors’ defence, while their defence was well marshalled by Seán Hoare.
Mark Timlin tested Hall again after a mazy run on 69 minutes before another deflection nearly went Pat’s way a minute later when Shaun Kelly got in the way of a long-range shot from Saints sub Graham Kelly but the Limerick keeper was again on hand to save.
Hall was helpless to stop the Saints second, however, as Fagan finally bettered the keeper, heading the hosts 2-0 up after 77 minutes. Timlin’s corner was headed on by centre-half Seán Hoare before Fagan nodded home.
The Pat’s striker was nearly on the mark again seconds later, but his shot zipped wide.
B Clarke; G O’Brien (c), D Dennehy, S Hoare, I Bermingham; C Byrne, L Desmond, K Treacy (G Kelly ht), M Timlin (D Markey 90), J McGrath (S Kinsella 86); C Fagan.
F Hall; S Kelly, Paudie O’Connor, R Williams, S Tracy (G Coughlan 86), S Kenny (S Russell 63); Paul O’Conor, S Duggan (c) , A Greene; L Lynch; C Mulhall (J O’Flynn 63).
B Connolly (Dublin).