Phoenix Patterson put Waterford in the driving seat in the other semi-final with a terrific brace as they beat Treaty United 4-1 at Markets Field.
Patterson raced in from the left to shoot past Jack Brady for the lead on five minutes.
The Londoner doubled that just before the half-hour when latching on to a pass from Junior Quitirna to finish for his 20th goal of the league season.
Quitirna fired a 40th-minute penalty off a post before Enda Curran converted a 62nd-minute spot kick to give Treaty hope.
That faded when Quitrina made amends to restore Waterford’s two-goal margin on 87 minutes.
A stoppage-time own goal from Seán Guerins all but puts Waterford into the final ahead of the return at the RSC on Saturday.
Jordan Adeyemo and Mikie Rowe swapped a brace apiece as Longford Town and Galway United played out a thrilling 2-2 draw at Bishopsgate in the first leg of the First Division playoff semi-finals.
Despite starting brightly Galway were behind on 29 minutes when striker Adeyemo, who started the season at Galway before a July move to the midlands, bounced a downward header past Conor Kearns from Darren Clarke’s cross.
Six minutes later the pair combined again as Adeyemo’s glancing header came back off a post.
Galway introduced winger Rowe at half-time and it proved inspired as he had them level inside four minutes, turning home a David Hurley cross at the back post.
The visitors then hit a post with a Stephen Walsh header from a Ronan Manning cross before Longford responded to regain the lead on 54 minutes.
Again the inspiration was Clarke on the right whose low cross found Adeyemo to shoot first time to the bottom corner of the net.
In end-to-end action, Galway levelled once more on the hour.
Killian Brouder’s long throw found Rob Manley whose header Luke Dennison could only parry.
Rowe was alert to the loose ball to stab it home off a post. The sides meet for the second leg at Eamonn Deacy Park on Sunday.
