By the close of day three, just 73 overs had been bowled as the rain continues to ruin the Specsavers County Championship Division Two clash at Bristol.
Gloucestershire are currently 220 for seven, having battled back from 80 for six during day three.
Graeme van Buuren was the man dismissed, with Gareth Berg getting the wicket.
But Ben Charlesworth will head into day four unbeaten on 77.
And Sanderson said: "We came into this game all excited, but it's turned out to be a bit of an anti-climax with the weather.
"When we finally got back out there, it was tough going, especially for the seamers.
"The outfield is a little bit soft still and there is very little life in the pitch.
"We'd have liked to have taken more than the one wicket, but the conditions were difficult for bowling.
"You have to give credit to Ben Charlesworth. He looks a really good player and, apart from me finding his edge on a couple of occasions, he didn't really look in trouble.
"We're still in a good position when it comes to promotion and we just have to rock up tomorrow and take these last three wickets.
"Then we can focus on batting the rest of the day and getting the job done."
Northants need a total of just four points from the game to make sure of promotion, and they already have two.
But they look guaranteed to go up as Glamorgan's game with Durham has also been affected by the weather.
That is also a help for Gloucestershire, who look set to celebrate promotion with Northants on Thursday.
Gloucestershire all-rounder van Buuren said: "We'd have taken this position had it been offered at the start of the day.
"Our main objective was to get past 200 and bank a batting bonus point.
"But 80 for six was a tricky situation and we just set out our stall to bat for a long time.
"They still caused us problems when they bowled straight, but it became easier the longer we stayed out there.
"In the end, the runs seemed to come quite quickly and we enjoyed ourselves. It was fun.
"Of course, I'm disappointed not to go on and make a hundred, but it's about the team and we're now in a good position.
"Ben Charlesworth is already a very good player despite being just 18. He stands tall and his cover drives really flow. He also knows when to leave the ball alone and his showed sound temperament today.
"We're a lot closer to being promoted now, but there is still work to be done and we need to stay humble.
"We have to come back in the morning and play like we would normally."