Dagenham & Redbridge continue to improve, but their victory was not unaided.
They were the better side in the opening period, but only led by a single goal and had come under intense pressure after the resumption as Northwich searched frantically for an equaliser.
Then in the 70th minute home full-back Greg Rioch was sent off after a touchline clash with Gary Fletcher and within 60 more seconds the visitors had scored their second goal and were able to relax.
Rioch's second red card in three games was for an alleged punch at former Northwich striker Fletcher although it seemed to be an attempt to fend off his challenge rather an assault.
Northwich defender Jake Sedgemore was perhaps lucky not to have also received a red card after only nine minutes.
As Junior McDougald raced into the penalty area, Sedgemore pulled him back and escaped with a yellow card while the Dagenham striker dusted himself off to strike home the perfect low spot-kick.
Fletcher, on a month's loan from Leyton Orient, came closest to increasing the visitors lead when he brushed off three challenges to fire fiercely at goal but Matthew Parry pulled off an excellent one-handed save.
Danny Shipp also tested the keeper and missed an even better close-range chance through wild finishing, while Paul Terry was another who should have taken more careful aim.
Vics were outplayed, but came close early on when a Mark Devlin cross found Richard Norris but his header was weak. A goalbound Devlin shot was also blocked by Lee Matthews just before the break.
After the resumption Northwich mounted a series of attacks which pinned Dagenham back and brought the best out of their defence.
A Val Owen header header from a Norris corner was just wide and started the goalmouth action. Owen was then the creator along with Kevin Street which gave Norris Northwich's best chance, but Tony Roberts smothered the ball at his feet.
Owen was also involved in a move which presented Gregg Blundell with a half chance but he curled the ball over the cross bar.
The sending-off of Rioch relieved the pressure on Dagenham because within 60 seconds and before Northwich could adjust Shipp had assisted McDougald to his second goal.
A swift move left the striker 12 yards from goal and his low shot went unerringly into the bottom corner.
In the closing stages only a goal-line clearance by Chris Royle prevented Shipp from increasing Dagenham's lead