Hello,
I have an Aprilaire humidifier model 445 attached to the return air. The problem is that the water in the reservoir constantly overflowed and flooded the floor. I had checked the folat-arm and the shut-off valve and they both seems working fine.

What I found out is by design the float-arm does not really stop the water from coming into the reservoir. In result, the water overflows inside the reservoir and onto the floor through a drain hole.

I really appreciated if anyone out there could shed lights on how to permanently stop the water from overflowing from the reservoir so I don't have to shut-off the incoming-water valve erery night, and emptying buckets of water.

 

It sounds like you may need a new float arm. They cost about 40-50 bucks which is about 1/3rd the cost of a whole new unit. I also think Aprilaire has discontinued some of the parts for this model but you can still find them online.

Here is their site and you can download a manual if you don't have one.

 

That's exactely what I did, changed the float arm and the shut off valve. At this stage, I am thinking the problem is a designing issue, and is looking for an alternate solutions.

 

Did it by chance come with a new float valve rubber stopper?

By the way I failed to put the site above sorry. It's not much help though for what yo need. http://www.aprilaire.com/

 

It should have, but I didn't check. I bought the kit.