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.
Welsh players and management joined Deputy Minister for Sport Ken Skates at the Pierhead Building, Cardiff Bay earlier this week to reveal the Union's pioneering school-club hub initiative has been so successful the project will now almost double the scale of the original project.
The Scarlets, Newport Gwent Dragons, Cardiff Blues and the Ospreys look ahead to Judgement Day III which sees the Blues take on the Ospreys (2.30) and the Dragons tackle the Scarlets (4.45pm) at the Millennium Stadium tomorrow afternoon.
Ystradgynlais and Ynysddu played out a titanic struggle at Taffs Well in the SSE SWALEC Bowl semi-final. At the end of the game neither team could be separated after a 15-15 stalemate but Ystradgynlais go through on try count.
Blues strike first in JD III battle - Newport Gwent Dragons lock Andrew Coombs, WRU referee Dylan Llyr Jones and Cardiff Blues hooker Matthew Rees decide dressing room allocations for Judgement Day III
Wales Under 18 captain Calum Haggett has received a conditional offer to read Biomedical Science at St Anne's College, Oxford. WRU chairman Gareth Davies went to meet Calum and Coleg y Cymoedd Principal Judith Evans to wish him luck in his exams and pass on some of his personal experience.
Dodgy tattoos, carthorses, Avatar and soft chins are revealed by Wales Sevens players Tom Williams and Sam Cross as they profile the Wales Sevens squad taking part in Hong Kong this weekend in the latest round of the HSBC Sevens World Series.