The hosts, who are now in third with a week to go, had a truly special performance by full-back David Gratton to help them to a seven-try, 46-13 triumph.
Gratton scored four tries and added seven points with the boot, while there were also scores by Dean Scarf (2) and Kyle Perry to see Rhydyfelin home.
Newport HSOB are now safe in Division Three East after a fine 13-3 victory at home to Rhymney. Captain Will Lowe scored the only try of the game late on and full-back Will Edwards added eight points with the boot as Newport secured another season in the division.
Pontypool United also got the point they needed to stay up, despite going down 17-16 against Croesyceiliog.
There is still all to play for at the top of Division Four East after Talywain went level on points with leaders Abertillery BP. But they missed out on what may prove to be a vital bonus point in beating New Tredegar, 26-20.
Luke Palmer, Martin Savage and Bevan Howells crossed for the hosts, whose final game is against third placed Risca on Tuesday evening.
Champions Oakdale failed to win for only the second time this season in Division Five East, as they were held to a 13-13 draw by Brynithel. Mark Perrot and Sean Pitt crossed for the visitors, while Trevor James hit back for Oakdale.
Already-relegated Pontllanfraith's miserable season continued as they lost 39-24 at Hartridge.
Beaufort were crowned champions of Division Six without taking to the field on Saturday, as closest challengers Cefn Fforest failed to get a bonus point in their 13-3 win against bottom side Cwm.