Chris Morris, Trystan Lazarus, Gareth Baker and Andrew Malin scored the tries for Treorchy as they were pushed hard for a 37-32 victory by Brynmawr.
There were also wins for Mountain Ash, Llantrisant and Newport Saracens, whose 34-19 victory over Abercynon was their first for almost seven months.
Aberdare as-good-as-ended St Peters' title challenge in the game of the day in Division Three South East. The home side scored tries through Matt Strong, Huw Williams and Humphrey Evans as they edged to a nervy 22-19 win to keep their own promotion ambitions alive.
They will do well to catch Penarth, however, after the league leaders steamrolled their way to a 48-5 victory over Llandaff North, centre Steve Roberts helping them on their way with a brace.
Llandaff's miserable season continued as they suffered an 18th straight defeat at home to Brecon, but Fairwater sealed what could turn out to be a vital losing bonus point in their 27-22 defeat at Hoel y Cyw.
It is sizing up to be an exciting finish to the season in Division Three East, as the top two sealed bonus point victories once again. Ian Davies scored a brace in Abergavenny's 31-5 win against Pontypool Utd. And there were two tries apiece for Daryl Cook, Ieuan Morris and Wayne Sims as Fleur de Lys kept up the pressure with a 56-12 trouncing of Croesyceiliog.
Dowlais look champions-elect of Division Four South East after all results went their way this weekend.
Number 8 Jonathan Pinch scored a brace as the leaders ended Taffs Well's title bid with a 25-19 bonus point victory.
Second-placed Cardiff HSOB are now 11 points off the pace after they went down 20-8 at Rhiwbina.
Centre Chris Stevens scored 28 points as Abertillery BG beat Machen 43-10 to strengthen their position at the top of Division Four East.