Tries from the impressive Sene Naoupu and Sophie Spence got them on their way, and while the second half was much tighter, they were never really threatened.
Niamh Briggs also played a key role, scoring 11 points with the boot and helping set up the second try of the game.
Wales made the better start and took the lead thanks to a penalty from young fly-half Robyn Wilkins as Ireland went off their feet at a ruck inside their own 22.
That was quickly cancelled out as Wales failed to clear their lines well from the restart, eventually caught holding on and Niamh Briggs responded in kind for the home side.
Ireland were beginning to get into the ascendancy in the territory stakes, and when Rachel Taylor drifted offside, the home side chose to kick to the corner. They forced another penalty and kicked back to the corner as they went for the try rather than settling for three points.
That proved to be the right call as Wales were penalised once more, this time Megan York was singled out for not rolling away and sent to the bin for her troubles.
Still, the Welsh defence proved hard to break down, and Ireland couldn't find a way through initially against the 14 men. They did finally cross for the first try through centre Naoupu, who broke through in midfield and had the pace to go all the way. Briggs converted to make it 10-3.
Naoupu was proving dangerous with ball in hand, and it was her fine pass wide that set Briggs away down the left on a good counter-attack. She found Mairead Coyne outside her, and although she couldn't go all the way, the ball was recycled for Sophie Spence to power her way over. Briggs couldn't quite convert from the touchline, but Ireland led 15-3 at the break.
Ireland started the second half on the front foot, and Briggs slotted a simple penalty just three minutes in to stretch the lead to three scores as the rain began to fall.
Wales should have got themselves back into it when their pack worked their way right up to the Irish line. After a couple of drives were stopped short, they decided to spread the ball wide and replacement Gemma Rowland couldn't collect, knocking on as the chance went begging.
Leading by 15, the win looked to be in the bag but when Ireland got another shot at goal, Briggs had no hesitation and tried to add three points. Her effort came back off the post though and Ireland were able to recover in brilliant position. Some good defence from the Welsh kept them at bay initially and eventually the Irish attack came to nothing as they were forced into a knock-on.
Briggs did another three points with 15 minutes remaining to stretch the lead a little further and despite a long period of possession in the Welsh 22, Ireland couldn't find a third try
England defeated New Zealand 49-46 to level up the three-match Series at 1-1 heading into the deciding match on Wednesday morning.
Sloane Stephens advanced to her first Grand Slam final at the US Open on Thursday night