The two sides were level-pegging at 2-2 going into the interval, but Llanarth, who have scored 20 goals in the last three matches, upped the ante in the second-half and destroyed Gilwern with five additional goals that were powered in to no reply.
Prolific striker Colin Morgan was in sparkling form and scored four for Llanarth, his brother Michael Morgan scored two and Luke Williams chipped in with one.
Matthew Burkitt scored both Gilwern and District goals.
Man of the match for Llanarth was Colin Morgan. Man of the match for Gilwern was new signing Tony Perry.
As a result of all other scheduled fixtures in the Premier League being postponed due to the adverse weather conditions, Gilwern hold on to second position and Llanarth stay in sixth.
Current Division One leaders Clydach Wasps drew 2-2 at home to a visiting Tranch side.
Scott Ambler scored a brace for the Wasps and man of the match was Stephen Davies.
Blaenavon Blues were also held to a 3-3 stalemate when they failed to knock out a result from their visit to Pilcs.
Man of the match Josh Bull (2) and Ryan Kean scored for the Blues.
Mardy won their local derby match against Govilon 1-0. The all-important goal was scored in the second-half by Mardy's man of the match Tom Copeland with a shot from just inside the box.
Man of the match for Govilon was Simon Phillips.
Second-placed Division Two side Clydach 'B' stormed to a 7-2 home win over Trevethin 'B' courtesy of a hat-trick by debut player Jasper Morgan, a brace by Luke Welsh and solo strikes from Nathan Wall and Anthony Hemburrow.
Man of the match for Clydach was Scott Dobbs.
And finally Usk Town 'B' were trounced on their own patch by Pontypool Town 'B' who beat them 0-3.