The home side, who play three divisions below their visitors from Division 3 South East, ran in two tries without reply to reach the next round.
The Gwent outfit had wing Josh Bratt and flanker Craig Drew to thank for their tries and outside half Leon Trezise chipped in with a penalty and conversion to clinch a notable triumph.
Other shocks came at Pontllanfraith, where Crumlin walked away with a 10-6 triumph thanks to an Aaron Farmer try, and at Cefn Coed, where a single penalty from Cefn Cribbwr fullback Chris Hooper was enough to edge a nail-biting contest, 3-0.
St Joseph’s won the battle of Cardiff as they dumped local rivals Llandaff out of the cup with a 12-11 victory. After trailing their visitors 6-3 the break, they went further behind when Llandaff No.8 Michael Morgan crashed over to make it 11-3.
But three penalties from fly half Gareth Cleaver were enough to see them into the next round at the expense of their higher league opposition.
There was an equally close affair at Cowbridge, where the Division Five South East triumphed 14-11 over beat Brynithel of Division Four East. There was a try hat-trick for Luke Riordan as St Peter’s smashed Division Three South East rivals Treorchy 45-0, while Cambrian Welfare recorded a fine result by beating Bryncoch 18-15.
Adam Ricketts and John Waller scored tries for Pyle as they beat Monmouth 21-15 and there were two tries apiece for scrum half Richard Morgan and flanker Anthony Clement in Blaengarw’s 39-5 thumping of Llanidloes.
