The leaders took a while to get into their stride, then raced clear by scoring six tries with fly half Mark David gaining a try, five conversions and a penalty goal, while skipper Karl Hocking notched his 116th league try.
The Old Parish also ran in tries by flanker Marcus Sainsbury, wing Gareth John, centre Alun Brown and wing Gareth Holmes, while fly half and skipper Stuart Morris placed three penalty goals for the Athletic in a game well controlled by Clayton Thomas.
Glamorgan Wanderers remained in third place despite beating UWIC 36-12, but are now just one point behind Llangennech with a game still in hand and a better try-count.
No 8 Emyr Christopher had an outstanding game and he, Mark Heywood, Dave Willey, Lee Mullane and replacement scrum half Gareth Spain went over with Heywood converting one and landing two penalties and Jason Pocock also placed a penalty.
The students ran in tries by Rhys Edwards and Gareth Dacey and Phil Dolman converted one.
Blackwood battled their way to a 25- home win over Builth Wells and went out of therelgation zone, moving over Fleur de Lys, Carmarthen Athletic and UWIC in the process.
Fly half Jeremy Lloyd led the way with a penalty, drop goal and two conversions and tries came from Jamie Sims (2) and Christian Perry, while Rob Lloyd placed a lone penalty for Builth Wells.
Bonymaen jumped from seveth to fifth place after a 30-0 win over Tonmawr, who now are staring relegation in the face and have eight game to survive, but are already 13 points away from safety.
Scrum half Gareth James, formerly of Penygraig, notched four of the five tries by the Parc Mawr club and wing Chris Griffiths also crossed with Anthony Evans placing a penalty and conversion.
WRU TV were on hand at the launch of a major new commercial deal with WRU and Mercedes-Benz South Wales (part of the Sinclair Group), which sees the family company become an official supplier to the Welsh Rugby Union
On the back of the recent Women's Rugby World Cup, the WRU has launched a revitalised Women's and Girls domestic seasonal structure, and the future is looking bright.
Go to www.wru.co.uk/tryourgame for more information
Roger Lewis talks to WRU TV at the announcement of a new £60 million Rugby Services Agreement (RSA) which provides a new and positive contractual relationship between the WRU and its four Regions for the next six years has been agreed.
The Welsh Rugby Union has announced a major new sponsorship deal with Gullivers Sports Travel which will make the UK's leading, and longest established, multi-sport tour operator, an Official Supplier for the rest of the decade.
Having taken part in seven World Cups as a player and coach, Liza Burgess hopes to go out in style this afternoon when Wales take on Australia in the Play-off for seventh and eighth place in the Women's Rugby World Cup in Paris.