Scott-Arrieta said he was stoked to get the series win in his last tilt.
"I'm definitely pretty happy with this one. I got higher scores in this event than in the other two events so that felt really good," he said.
"It was my last year in the Under 20s so the goal was to take it out. I'm really stoked to have won all three events."
The conditions at Piha weren't as brutal as they could have been but that didn't reduce any enjoyment on Scott-Arrieta's end.
"It was a little bit slow at times but super fun when you caught the waves," he said.
"There wasn't many people that entered in the event but they were still good surfers. I had to give it my all.
"It would have been nice to have some more people competing so we could surf a few more rounds though."
Meanwhile, Scott wasn't able to claim the third leg of the series in her Under 20s division but second was good enough to secure the overall title.
Raglan's Indica Ratima took out the Piha event with a score of 10.24 in the final, heading off Scott by 9.17.
Scott started the series with a commanding win in the first round at Mt Maunganui before finishing third in the Piha leg.
Four other Northlanders were in action in the Piha event.
Tom Robinson was denied the Under 16 Boys' title after finishing third at Piha. Needing a second place finish to secure the win, Robinson scored a strong 12.56.
However it wasn't enough to beat Whakatane's Jack Lee (15.16) and Tom Butland of Oakura (14.7).
Meanwhile, Whangarei's Max Brunker and Waipu's Tom Norton were in action in the Under 18 Boys'.
Brunker won his semifinal to progress to the finale however Norton was eliminated in a high scoring playoff.
Brunker couldn't replicate his form in the final, settling for fourth as Hamilton's Caleb Cutmore dominated proceedings.
Te Kauwhata Kauwhata was unlucky not to finish higher in the Under 14 Boys' division.
The Sandy Bay surfer got tangled in a double interference with Christchurch's Dara O'Malley in the final, scuppering any chances of a win. They finished third and fourth respectively.