Setefano Sauqaqa and Anthony Tailua both scored hat tricks for the home team, with James Lash converting six of seven conversions to lead the overall points scorer table on 84.
However, after an easy fortnight, Buller now have a tough row to hoe with two away games from their last three matches against Wairarapa Bush, Wanganui and King Country respectively.
Thames Valley had been winless but competitive with every opponent so far in 2016, yet South Canterbury blew that consolation away with a 62-16 mauling in front of disappointed spectators in Paeroa.
South Canterbury scored nine tries to two, including receiving an automatic eight-point penalty try, while centre Cameron Bailey and new winger Kalavini Leatigaga each got a double.
Mid Canterbury and King Country both moved ahead of North Otago to stay in touch with the Meads Cup group.
Hosting West Coast in Ashburton, Mid Canterbury picked up the expected bonus point win, but did not have it all their own way, coming from behind at halftime in the 34-22 victory.
Jarrad Percival got two tries for the hosts and Erenimo Tau did the same for the visitors.
Bouncing back from the Wanganui defeat, King Country got another important win on the road by seeing off Horowhenua-Kapiti 42-18 in Levin.
Winger Ralulu Bavov scored two of their six tries.
Results, September 24.
South Canterbury 62 (Kalavini Leatigaga 2, Cameron Bailey 2, Hamish Strachan, Mathew Etheredge, Kieran Coll, Maxx Morris, penalty try; Willie Wright 2 con, Bailey con) bt Thames Valley 16 (Hayden Wisneski, Ben Bonner tries; Moss Doran 2 con). HT: 28-16.
Wanganui 52 (Rangatira Waitokia 4, Michael Nabuliwaqe, Lindsay Horrocks, Campbell Hart tries; Steve Crosbie pen, 4 con) bt Poverty Bay 30 (Siosiua Moala, Dan McIntyre, Body Allen, Jacob Cook tries; Isaia Vuki 3 con). HT: 20-14.
Mid Canterbury 34 (Jarrad Percival 2, Christian Vainerere, Jon Dampney, Mike Lynch tries; James Percival 2 con) bt West Coast 22 (Erenimo Tau 2, Brogan Watt tries; Nic Cumming 2 con). HT: 16-12 West Coast.
King Country 42 (Ralulu Bavov 2, James Hemara, Gene Waller, Alex Thrupp, John Koko tries; Zayn Tipping 3 con) bt Horowhenua Kapiti 18 (Rahiri Connor Johnson, Aaron Lahmert tries; Perry Hayman pen, con; Lahmert pen). HT: 14-10.
Wairarapa Bush 38 (Andrew McLean, John Ika, Glenn Walters, Iziq Foa'i, Zac Guildford tries; Tim Priest pen, 3 con) bt North Otago 22 (Shay Tucker, Filipo Veamatahau, Lemi Masoe tries; Josh Casey 2 con).
Buller 54 (Setefano Sauqaqa 3, Anthony Tailua 3, Scott Neighbours tries; James Lash 6 con) bt East Coast 22 (Long Fisiioi 2, Ben Parkes tries; Todd Doolan 2 con).