Fly-half Adrian Jarvis kicked three penalties at a rain-lashed Twickenham Stoop as Quins prevailed 9-3.
A sodden playing surface effectively made running rugby impossible, and it was the Quins pack that underpinned a winning performance by outplaying a Bath eight that sorely missed suspended England forwards Danny Grewcock and Lee Mears.
Rugby director Richards said: "Our flanker Andre Vos came off at the end and said they were probably the worst conditions he had ever played in.
"It was obviously pretty difficult out there, but we will take the win. Our forwards were outstanding throughout the game - they played extremely well.
"We didn't always take the right options, but our forwards won us the game.
"It was one of those days when I think the first time the backs saw the ball was when they came into the changing room at the end of the game."
Quins have now won six games following their return to the Premiership this season, but Richards expressed disappointment that more of his players did not gain recognition in either England's RBS Six Nations squad or England's Saxons party that were both announced earlier this week.
Four players from Quins made the Saxons group, but Richards expressed surprise that scrum-half Andy Gomarsall did not make the senior contingent.
Richards added: "I am surprised that Andy did not make the senior squad, and I thought generally, we might have had more players involved, such as flanker Will Skinner and centre Jordan Turner-Hall."
Bath were a shadow of the side that defeated Wasps five days ago, and although they left London with a losing bonus point it was a source of little comfort for head coach Steve Meehan.
He said: "We are very disappointed with that loss. We had some opportunities in the second half, and we should have nailed that game.
"At half-time, we were quite happy with things even though we were 6-0 behind, but we didn't manage the first 20 minutes of the second half very well. We have only got ourselves to blame."
Bath at least saw skipper Steve Borthwick emerge unscathed from his first appearance since undergoing knee surgery in September, but overall it proved a miserable day for the West Country club.