But the northerners went over before half time and added a further three tries in the second half to stay four points clear of nearest rivals Ystrad Rhondda, who have a game in hand.
Rhydyfelin scored a staggering 18 tries against bottom-of-the-table Tredegar with hat-tricks apiece for Lloyd Peart, Ross Lucas and Rhys Chinnuck all contributing towards a 114-10 scoreline.
In Division Two, Bedlinog remain at the top despite dropping points at fourth-placed Senghenydd – the match finished as a 6-6 draw.
Rhiwbina ensured a close end-of-season run-in after they moved to third position after brushing aside Fleur De Lys in a 29-8 home win. There are now only four points separating leaders Bedlinog and their opponents today, Senghennydd, with Nelson and Rhiwbina occupying the second and third spots respectively.
Elsewhere, Abertillery BG edged closer towards the Division Three title after securing a bonus point victory against second-placed Newport HSOB. The league leaders, who are now nine points ahead at the top with only six games remaining, went over four times to earn a crucial 27-7 away win.
