Scrum-half Lewys Gibby’s try, along with a conversion and four penalties from Jonathan Rogers, maintained the Otters’ 100 per cent winning record and moves them 10 points clear of Llangennech.
Brecon outscored Narberth two tries to one with wing Tom Richards and captain Alwyn Lee their scorers. Dion McIntosh kicked the other five points.
For Brecon, it was only their second league defeat of the campaign and a first on the road. Dale McIntosh’s men now sit third and are 13 points behind Narberth having played one game less.
Ammanford edged Crymych 25-24, helped by tries from Elis Lewis, Kai Richards and Sam Potter – who also kicked 10 points. Meanwhile, Morgan Jones, Sam Martin, Alex McNamara and Steff Lewis were all among the scorers as Trebanos defeated Tata Steel 29-7, with Rhys Harris adding three conversions and a penalty.
Ystalyfera saw off Dunvant 39-21 while Bonymaen were 34-14 victors over Maesteg Quins.
Admiral Championship East leaders Ystrad Rhondda won 22-19 with a bonus point at Rumney thanks to tries from Kurtis Williams, Lucus Welsh, Jarrad Llewellyn and Lewis Williams. Rhys Truelove added a conversion.
Nearest challengers Cardiff Met remain four points behind with two games in hand but left it late as they had to come from behind before edging out Beddau 33-31 in a thriller.
Jamie Savery, Osian Hill, Porter Goodrum and Toby Baldwin scored for Met. Sam Berry kicked two conversions and three penalties.
Callum Wheeler scored twice for Beddau, who were 21-16 up at the break and then 31-21 ahead in the second half. Harri Bryant and Ethan Coombs also scored. Hywel Chatham kicked four conversions and a penalty.
There were huge wins for Penallta, 73-18 over Treorchy, and Cross Keys, 55-19 at St Peter’s while Glamorgan Wanderers got the better of Newbridge 29-17. The Wanderers picked up a bonus point thanks to tries from Ned Bennett, Steff Davies, Finn Davies, George Cottrell, while Ceri Morris kicked 12 points.
