You get what you pay for...

Paul thought he would try and save some money replacing our heater's Aprilaire humidifier pad himself. He went down to Lowes and bought an aftermarket the pad.

Suddenly our humidifier started leaking water.

After the heating serviceman came twice, we figured out that the replacement pad was slightly thinner (as seen below) than the original manufacturer pad. The serviceman speculated that the thinness allowed the pad to flex when our heater's fan goes into a burst mode (if after running for 10 minutes the fan kicks on high if the desired temperature is not reached) thus causing it to leak. Putting in the original Aprilaire pad fixed the problem. The cost to figure it out? Don't ask Paul...he's still a little tender on that.

The original manufacturer pad on the left...
...is about 1/4 thicker than the one Paul bought on the right...