We have a whole home humidifier as part of the furnace system, but have never really used it since we bought the house. I'd like to get it up and running and am trying to figure out some update maintenance before using it.

There is a copper water line that goes through an inline water filter, which then goes to the humidifier evaporator pad filter, also through copper piping. I figured I needed to change the water filter since it was there when we originally got the house. The problem I'm running into is if I can just "unscrew" the inline filter and replace it, or if I'm going to have to cut the copper line or something. It appears that there is a coupling that goes into the filter, and it has that piping tape applied or something. I tried twisting it a little to see if I could force it to unscrew and it felt like the copper tubing was going to start shearing so I backed off.

Below are some pics of the filter.

The filter AP717 filter

Bottom coupling of filter Bottom coupling of filter

Top coupling of filter Top coupling of filter

I guess what I'm looking for is what do I need to do to replace this filter? Should it be able to just unscrew and screw a new one in? Is it just a matter of a couple wrenches and getting the filter to move?

It doesn't feel that easy, but I don't know if that's because it's pretty old or if it was installed in a more "permanent" fashion that what it should have been in the first place. Once I get the filter replaced getting the rest up and running should be pretty straightforward.

1 Answer 1


This filter appears to be a single unit, so the way to replace it would be to disconnect this one and install a new one. First make sure the water supply to your humidifier is off.

The attachments look like 1/4" copper compression fittings. If you look at the fittings in top-down order on your second pic, you have first the copper tubing, then a nut which is clamping the compression fitting onto the copper, then a male adapter that threads into the filter inlet. To disconnect the filter use one wrench on the plastic "nut" at the end of the filter to hold it steady, and another wrench on the adapter (the brass part closest to the filter). Should be a normal counterclockwise unscrew operation.

Then you can reuse those fittings with a new filter. Alternatively, you can cut the copper tubing and install new fittings with your new filter.

You're probably looking for an "ice maker filter" like this: https://www.amazon.com/LASCO-37-1821-Compression-Connection-10-Inch/dp/B00HYXR24S/ref=sr_1_3?s=appliances&ie=UTF8&qid=1514872086&sr=1-3&keywords=water+filter+1%2F4%22

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