The home side, who play Munster in the Heineken Cup next week, were so dominant they had sealed a bonus point within the hour as they scored 25 unanswered points straight after the break.
The Scarlets dominated the early exchanges but it took them 18 minutes to open a 7-0 lead.
Wales scrum-half Dwayne Peel crafted the score with a kick ahead which evaded the outstretched hands of Kevin Morgan, allowing Ceiron Thomas to follow up his own kick to beat Aled Brew to the touchdown.
From a scrum the Dragons earned their first points – a 32nd-minute penalty for Ceri Sweeney.
That was cancelled out by a penalty for Thomas three minutes later and there were more problems for the Gwent region when replacement hooker Richard Wilkes was sin-binned for a blatant piece of ball-killing.
But despite being down a man Sweeney cut the Scarlets’ half-time lead to 10-6 with an injury-time penalty.
Less than two minutes after the break the Dragons were down to 13 men with Brew seeing yellow from referee Phil Fear for slowing ball in front of his posts.
A second Thomas penalty goal was sandwiched between two fine Scarlets tries. First Barry Davies outstripped Morgan to the line and skipper James Bater showed an impressive turn of pace to successfully chase his own kick ahead.
And the search for a bonus point did not take long with Wales wing Mark Jones breezing over in the left corner on 62 minutes for the fourth score.
The Scarlets had not finished there with replacement wing Dafydd James claiming the fifth try before Morgan grabbed a consolation eight minutes from time.
Tries: C. Thomas, B. Davies, Bater, M. Jones, James. Cons: C. Thomas 2. Pens: C. Thomas 2.
B. Davies, M. Jones, King, G. Evans, Daniel, C. Thomas, Peel, I. Thomas, Gravelle, Manu, Afeaki, MacLeod, Bater, G. Thomas, N. Thomas.
James for Daniel (47), Stoddart for C. Thomas (79), L. Davies for Peel (65), J. Davies for I. Thomas (79), Rees for Gravelle (50), A. Jones for Afeaki (58), Mills for G. Thomas (70).
Tries: Morgan. Pens: Sweeney 2.
Morgan, Wyatt, Emerick, P. Dolman, A. Brew, Sweeney, Cooper, Black, Daly, Harrison, Charteris, Sidoli, Charvis, Ringer, Owen.
A. Thomas for Emerick (75), Maule for P. Dolman (66), Walker for Cooper (69), Corsi for Black (43), Wilkes for Daly (19), Hall for Charteris (64), Fitisemanu for Owen (64).
Phil Fear (WRU).
By John Scott
SLOOPY Edinburgh surrendered their slim hopes of claiming the Magners League crown as they were sent crashing by the Borders basement boys in an error-strewn affair at Netherdale.
Garry Law emerged as the villain turned hero for the Reivers, who bagged their first triumph in 15 games.
Law squandered three easy penalty opportunities – but made ample amends with the try that made all the difference.
Edinburgh earned the first scoring opportunity when the hosts were guilty of failing to release the ball in contact – and stand-off Duncan Hodge confidently slotted the 35-metre penalty.
Having weathered the early storm, Reivers hit back with a series of midfield surges featuring Gregor Townsend.
They pressured Edinburgh into giving away an offside penalty – but Law sent his effort sailing wide of the near post.
Borders kept up the momentum – but there was yet more gloom as Law made a hash of another simple penalty attempt.
It was third time unlucky for Law two minutes later when he sent his next kick crashing against the upright, the ball rebounding to safety.
Jones took over the boot duties and he levelled the issue from close range after Ally Strokosch was spotted swinging a fist in his own danger zone.
Law’s fortunes changed just after the restart when he scooted over for an excellent touchdown.
Jones slotted the conversion from a wide angle to open up a seven-point gap, they would never relinquish.
Tries: Law. Cons: Jones. Pens: Jones.
Moffatt, Flockhart, MacDougall, Rennie, Law, Townsend, C. Cusiter, Kerr, Ford, Douglas, Dalziel, Palepoi, Newlands, Brown, Miller, Daniel.
Daniel for MacDougall (8), Jones for Daniel (22). Not Used: Scott, Kalman, Chrystie, Vernon, Forrest.
Cairns, Dey, Di Rollo, Dewey, Lopez Fleming, Hodge, Senio, Jacobsen, Hall, G. Cross, Mustchin, Murray, Strokosch, Callam, Hogg.
Warnock for Cairns (45), Godman for Hodge (45), Laidlaw for Senio (73), Rennie for Hogg (73).
Neil Paterson (SRU).