The Irish still have two tough encounters to come in this year's championship.
Wales have started strongly.
The second half began where they left the first with a score and it was Dan Leavy under the posts, Sexton again made no mistake with the conversion.
Farrell kept the visitors in touch with two penalties, but their attack was lethargic and in defence they simply could not contain Scotland with Russell and Jones combining to create the field position for Maitland to dive over in the corner.
Ireland finally imposed itself in the third quarter.
Ireland v Wales games are traditionally tight and this one was no exception, the excitement lasting until the final minute.
In the 61st minute Wales had a big overlap on the right flank and Aaron Shingler danced over for his first try for his country. A Bundee Aki try on the cusp of half time settled Irish nerves.
Old scars do not need to be reopened, but the reality is, since that terrible afternoon in Cardiff, Ireland have posted wins over both New Zealand and England while they also ran the two-time defending world champions very close in Dublin in 2016. The Welsh looked deflated. But Wales, who had played well in patches up to that point, were to have another burst at the Irish defence to set up a nervy finish.
Gareth Davies showed a lovely sidestep to score his try but in reality it was Wales' only try-scoring opportunity of the half. Sexton made it 22-13 with a simple conversion.
And even when Conor Murray slotted a penalty to take Ireland's lead to ten points, Wales hit back with a Steff Evans try. I think we need to take every game as they come.
After starting the tournament hampered by injuries, Wales welcomed back three British and Irish Lions while Ireland lost three of their own.
With Warren Gatland's side having to go for a try, a long pass out was intercepted by the alert Ulster winger Jacob Stockdale, allowing him score his second try on the day, his eight to date at worldwide level.
Ireland winning the game 37-27, but the game was on a kife edge the entire way while an intercept try from Jacob Stockdale inside the 80th minute put gloss on the score. The usually so-reliable Johnny Sexton had an off day with his place kicking, missing three kicks at the posts in the opening 15 minutes.
Wales - Tries: G Davies, Shingler, Evans. Halfpenny's stunning touchline conversion pushed Wales within seven points, but there was to be no stirring comeback.
The second half seen Ireland fly out of the blocks as Leavy and Healy added to further tries to give the boys in green a well deserved bonus point.
"When I came to Leinster, he was playing at loosehead, and having coached the likes of Dan Cole, Kyle Sinckler, and Kieran Brookes as the English tightheads I was, 'Who's this kid?' We all made the collective decision, Leinster and Ireland, that he should be looked at as a tighthead, and he's going to be some player".
Scott Evans instantly responded with a try for Wales but an astute CJ Stander prevented the winger from touching down under the posts, ensuring Halfpenny had a more hard kick for the conversion.
Poor discipline continued to plague Wales and a mindless offside handed the hosts a penalty which Sexton booted deep into the Welsh 22 with half-time less than a minute away.