Takahiwai and Portland were then reduced to 12 players, Portland permanently, after a midfield scuffle.
As the rain began to cascade down and with each team down a man, both sides continued to make errors.
Takahiwai were particularly guilty of penalties, conceding three in five tackles to give Portland great field possession.
Another grubber, this time from Portland standoff Kass Wall, put winger Zac Pere Epiha over in the corner for the equaliser.
It looked as if the game would be level going into the break but the reintroduction of Takahiwai hooker Charles Tarau from the sin bin proved a difference.
Centre Joel Suvalko made the most of some open space to brush off two would-be defenders to extend Takahiwai's lead to 12-6.
Takahiwai continued their momentum in the second half as they continued to set the pace.
Ross McFarlane, who put in another industrious effort at centre, was rewarded with a try on the left edge.
Portland were feeling the pinch from having one less defender on the field, despite the best efforts of slippery fullback Stilie Antonio.
Takahiwai started trying - and pulling off - different moves close to the Portland line.
The highlight of these was a fifth tackle run from Kyle Hool. He threw a dummy, put on a step and found Jordan Hool on his inside shoulder for a brilliant try.
Portland were becoming their own worst enemies with ball in hand. Their pack would make good runs but the side were too often guilty of spilling the ball before the last tackle.
After conceding another penalty, Portland were slow to get back onside. Kyle Hool saw this and took a quick tap, racing 45m untouched for his second try.
Takahiwai added another four-pointer near the full-time whistle through prop Ed Wilson after Portland missed touch off a penalty.
Meanwhile Otangarei Knights were made to work hard by Hikurangi Stags, taking out a tough 24-16 win.
Northern Wairoa Bulls were the other winners in the final match-ups of round one, beating Hora Hora Broncos 24-18.
