It followed a round 3 heat victory in which he scored 14.24 (6.67, 7.57) to topple deVault (12.30), Frenchman Charly Martin (11.66) and Brazilian Marcos Correa (10.50), the top two advancing.
Christie won his first heat of the contest — he was seeded into round 2 — with a 13.04 (6.27, 6.77) score, with Argentinian Santiago Muniz (11.93) second and also moving through to round 3.
The event has thrown up some shock results including the exits of defending champion Jordy Smith and Brazilian Willian Cardoso, both Championship Tour competitors.
Christie went into the Ballito Pro 59th on the QS rankings. It is one of only five QS contests offering 10,000 ranking points, and getting as far as he already has will move him up the rankings.
His best result so far this season is 17th at the Ichinomiya Chiba Open in Japan last month.
The top 10-ranked surfers on the QS qualify for the 2019 CT.
Christie made it to the 2015 CT — only the second Kiwi male to achieve the feat — but failed to retain his place.