In an open fluid game, neither side managed to cross the line in the first half, though not for want of trying
Wasps scrum-half Peter Richards denied Scott Staniforth by preventing him from grounding the ball after centre Nils Mordt sent him in between the posts in the 28th minute.
Then Irish looked almost certain to concede when Rob Hoadley intercepted a telegraphed pass from Mark Mapletoft and kicked over the defence, but under pressure from lock Nick Kennedy he just failed to grasp the opportunity.
Mark Van Gisbergen, impressive with the boot, landed four first-half penalties to take Wasps in 12-9 ahead at the break, with two Mapletoft penalties and a drop goal comprising the Exiles' points.
Hoadley, who joined Wasps from London Irish during the summer, returned to the Madejski Stadium to make the breakthrough against his old club when Simon Shaw's short pass sent him in for the opening try in the 43rd minute.
Then, with Irish down to 14 men after Paul Gustard's sin-binning, Tom Voyce's strength took him through the Irish defence for Wasps' second try in the 56th minute.
Two minutes after that, an excellent passing move ended with an easy try for replacement lock Richard Birkett who went over unchallenged, and the game was over as a contest with Van Gisbergen faultlessly converting all three tries.
Irish right-wing Scott Staniforth ran in a late consolation try, and Barry Everitt, who had replaced Mapletoft, added the conversion to become the fourth Premiership player to reach 1,000 points, joining Jonny Wilkinson, Tim Stimpson and Paul Grayson.
Wasps piled on the pressure in the closing stages in an attempt to grab a bonus point fourth try but they were denied by some desperate defending from Irish.
For London Irish:Try: StaniforthCon: EverittPens: Mapletoft 3Drop goal: Mapletoft
For Wasps:Tries: Hoadley, Voyce, BirkettCons: Van Gisbergen 3Pens: Van Gisbergen 4
London Irish: 15 Michael Horak, 14 Scott Staniforth, 13 Rodd Penney, 12 Nils Mordt, 11 Justin Bishop, 10 Mark Mapletoft, 9 Darren Edwards, 8 Phil Murphy, 7 Kieron Dawson (c), 6 Paul Gustard, 5 Bob Casey, 4 Nick Kennedy, 3 Rob Hardwick, 2 James Van Der Walt, 1 Neal Hatley Replacements: 16 Doug Wheatley, 17 David Paice, 18 Ryan Strudwick, 19 Roland Reid, 20 Declan Danaher, 21 Barry Everitt, 22 Paul Hodgson
Wasps: 15 Mark Van Gisbergen, 14 Tom Voyce, 13 Ayoola Erinle, 12 Rob Hoadley, 11 Michael Roberts, 10 Alex King, 9 Peter Richards, 8 Lawrence Dallaglio (c), 7 Tom Rees 6 John Hart, 5 Martin Purdy, 4 Simon Shaw, 3 Craig Dowd, 2 Phil Greening, 1 Tim PayneReplacements: 16 Ben Gotting, 17 Will Green, 18 George Skivington, 19 Richard Birkett, 20 Warren Fury, 21 Matt Priscott, 22 James Brooks
Referee: Roy MaybankTouch judges: Peter Huckle, Bob Mullis