Scarlets (10) 16
Munster fly-half Ronan O'Gara kicked 19 points in poor conditions
Pens: Priestland 3
Munster (22) 29
Tries: Wallace, Horan
Cons: O'Gara 2
Pens: O'Gara 5
Munster moved to the top of Pool Five with a powerful Heineken Cup win over Llanelli Scarlets played in atrocious conditions at Stradey Park.
Fly-half Ronan O'Gara played the wind and rain perfectly, kicking sensibly for position and booting 19 points.
Scarlets scored a try first through Regan King, but David Wallace romped over before half-time for Munster.
Rhys Priestland kicked Scarlets within striking distance only for Marcus Horan to barge over to seal Munster's win.
Munster enjoyed the early territory and possession, with captain O'Gara easing the visitors into a 6-0 lead with two penalties.
A superb break from Dwayne Peel seemed likely to give the Scarlets their first points but a fine cover tackle from Lifeimi Mafi dragged the scrum-half down just short.
However, the centre then failed to regain his feet as he tried to wrestle the ball away from Peel and referee Wayne Barnes had no hesitation in sin-binning Mafi.
Priestland converted the resulting penalty, before a searing break by Mark Jones saw King dive over, Gavin Evans providing a crucial link to see the Scarlets lead 10-6 with the conversion.
But O'Gara continued to chip away and added two more penalties either side of Scarlets wing Jones being sin-binned, referee Barnes consistent in his dislike of players killing the ball.
Munster took control as the half closed when they caught the Scarlets snoozing, taking a quick line-out to send flanker Wallace away and under the posts without a hand laid on him.
The simple conversion and a late penalty from O'Gara, his fifth, saw Munster lead 22-10 at half-time.
Already wet conditions deteriorated sharply in the second half as the rain came flooding down, leading to fears that the match could be abandoned.
But thankfully the deluge eased slightly, albeit not without leaving the pitch a quagmire, and Priestland made light of the conditions with two fine penalties to bring the Scarlets back into range.
Any hope of a comeback disappeared when prop Deacon Manu was sin-binned for foul play.
It left the Scarlets short-handed in defence and Munster took advantage, shunting prop Horan over from close range for another seven points.
While Munster now top the pool on 10 points following Clermont Auvergne's home win over London Wasps, things look bleak for the Scarlets.
Although not mathematically out of contention, the Welsh region are rooted to the bottom of the table without a point to their name.
Llanelli Scarlets: Stoddart; M. Jones, King, G. Evans, Brew;
Priestlend, Peel; I. Thomas, Hayter, Manu, Eustace, MacLeod,
Easterby (capt), G. Thomas, D. Jones.
Replacements: J. Davies for Brew (62), Cooper for Eustace (50),
Popham for D. Jones (50).
Not Used: George, Douglas, Cattle, C. Thomas.
Sin Bin: M. Jones (34), Manu (69).
Munster: Payne; Carney, Tipoki, Mafi, Dowling; O'Gara,
Stringer; Horan, Flannery, Hayes, O'Callaghan, O'Driscoll,
Leamy, Wallace, Foley.
Sheahan for Flannery (64).
Not Used: Buckley, D. Ryan, G. Hurley, Lewis, Warwick, Coughlan.
Sin Bin: Mafi (19).
Ref: W Barnes (RFU).