OP could still have a mid efficient furnace and the condensate line he refers to is the one from the AC coil. The Op mentions he turns the "main " off and water doesn't pool.... Not sure what they mean by "main"
Disconnect drain at humidifier, apply a bucket to catch water. Energize a call for heat and humidity, go down and confirm water draining from humidifier. Now remove the call for humidity and leave furnace heating, check again for water drainage from humidifier like before. If it stops your humidifier is working normally and the Lil' Giant condensate pump could be the issue and the float is stuck or the motor itself is seized. Remove the call for heat now.
If humidifier would continue to run with the call for humidity removed, confirm 24 volt power circuit to it is de energized in which case you would possibly require a new solenoid valve. These may or may not be avail at the retail level depending on brand of humidifier.
It's been 5 days since the post, I'm guessing things have been repaired/solved.
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