Aprilaire 760 humidifier

My house has this unit attached to the furnace installed by the previously owner. Problem is, it leaks. Water pours out of the unit. Is there some sort of filter in there I need to replace?

Have you checked www.aprilaire.com?

They have owners manuals for different units online and will show you how to open the unit and replace the media pad. You may also have a clogged drain line - again, the drawings in the owners manual will help figure this out.

This humidifier works sort of like an evaporative cooler. It runs a stream of water down a filter panel. Air moves through the panel evaporating most of it, then any excess flows out the discharge tube. The water that doesn't evaporate has most of the minerals concentrated in it, but some is deposited on the filter material, eventually making it nearly useless. Some humidifiers recirculate the water with a pump from a reservoir, this one (if I read it right) doesn't. If there is no filter material in there, or if it is all scaled up, it won't allow any water to flow through it, only over it, and it won't work very well as most of the water will just run down the drain rather than wetting the filter. The filter material needs to be replaced, probably at least once a year, and maybe more often. I found some replacements on-line that were about 1/4 the cost of the OEM parts...seem to work okay, but aren't quite as thick. Some of the big box stores carry them. This model is not current, but the user manual is here: http://www.aprilaire.com/themes/aa/en/manuals/Humidifiers_Owners_Manual.pdf