I had the cold water running in the bathroom sink in the almost finished basement (just lacking finished flooring).
After about 10 minutes water was noticed coming from the opposite wall of the sink on the floor, the whirlpool tub started filling up and the toilet would not flush.
I turned the bathroom light on and the whirlpool tub started draining and the toilet would flush. It sounded like a pump came on. The whirlpool tub and toilet were built up about six inches.
Could this be a waist water pump to pump up to the septic tank?
Why would this be controlled by an unmarked light switch?