Worcester, who have now lost all nine of their Aviva Premiership games this season, had been ahead at the break as Ignacio Mieres' try and conversion made it 7-6.
But the hat-trick of scores from Northampton allied with 18 points from the boot of Stephen Myler maintained Saints' charge at the top of the table.
Myler had put Saints 6-0 up early on as his team looked to assert their authority from the off.
It was taking time for the second-placed side to break the Worcester line, but when they did Ken Pisi was denied a try by the TMO, who ruled there had been a forward pass in the build-up.
It was the only time in the first half an hour that the Warriors had looked likely to be breached with the game being fought out in the middle third of the pitch.
But there was to be some action in the Saints 22 before half-time and it was costly for the away side as Glenn Dickson had his kick charged down and Mieres scored.
The Warriors No.10 kicked the conversion to the delight of the home fans, giving them reason to believe their team's fortunes could be about to turn.
They nearly had a second try before the break as Mieres' penalty attempt rebounded off the bar and Chris Pennell just failed to find Dean Hammond from the resulting move.
And Worcester were ahead for just six minutes at the start of the second period as Myler landed a penalty to make it 9-7.
Hammond's clever play put Saints back on the back foot, though, and they conceded another penalty, which Pennell slotted to make it 10-9 to the home side.
James Stephenson then covered well to stop Collins touching down, but the Warriors couldn't keep Northampton out as pressure built from the lineout.
Second row forward Manoa was the man to stretch an arm out to score after his fellow forwards pushed their way towards the line.
Myler made it 16-10 to Saints before adding a penalty to extend the lead to nine points.
Worcester had been in the game for so long, but they were starting to struggle and Collins took the game out of sight as he dived over in the corner for his first senior score.
Myler made the conversion and Wood stormed over soon after to leave Saints with six minutes to get the bonus-point fourth try.
But Worcester put a stop to that possibility as Northampton were forced to settle for the four points.
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