Tata arrived seeking their first win of the season, but it turned out to be unlucky 13 as they slipped to another defeat 19-10 as they remain rooted to the bottom of the table.
Home tries came from lock Morgan Bevan, flanker Jamie Nicholas and wing Jack Coker, with centre Joe Packer adding two conversions.
Victory in the only game that beat the weather in the West enabled Dunvant to leapfrog Crymach and put pressure on the top three.
In the East, the only game played was at Beddau, where struggling Treorchy were the visitors. It ended in a comfortable 32-12 home win.
The home side started off like a runaway train as they scored a point a minute in the opening quarter. Full back Cody Baker kick-started matters with a penalty and a try and then added the extras to a touchdown from flanker Cai Herdman.
Adam Ashford then finished off a great break by co-centre Sam Edwards to make it 20-0. To their credit, bottom of the table Treorchy mounted a fightback with two tries of their own before the break, the first from a driving line-out, and it the game was still up for grabs at the start of the second half.
But Beddau finished with a flourish as wing Ewan Roberts scored two more tries to bag the bonus-point.
