Humidifiers and Dehumidifiers - Installing humidifier on a joint

I've read that I can install my Aprilaire 600 anywhere on the return duct. Does this include over a joint? Obviously, a nice, flat part of the return would be ideal, but because of the placement of my water heater, that's not an option.

Just to be extra clear, the joint is nothing special--it's just where the installer joined together two pieces of ducting. One piece fits inside the other, and the sheet metal on the "outside" duct is doubled back over on itself to form a 1-inch band with a 1/2 inch lip that sticks out perpendicular to the duct itself. The return duct is 25" wide. I would cut the hole so that this joint would be roughly in the middle (half of the hole above the joint, half below).

I'm assuming that the function of that lip is to give the duct some lateral stiffness--in other words, it reinforces the side and keeps it from being able to flex in and out too much. Am I risking anything by placing my humidifier in this spot and removing part of the joint?

I've never done it that way.... I would try to do away from it if possible.. If you can't, just make sure that area is stiff.. Otherwise, when the fan kicks in, the duct may "pop" on you.

Dont do it . Thats what is called a T bar or T slip its to help hold that 25" so the duct dont go in and out when the blower comes on If you do cut it put a new one above and below the humidifier across the duct.

ED ;)

Good to know. This is exactly what I was concerned about. I was able to make just enough room for the humidifier on the flat part of the return duct by moving the shutoff valve on the cold water pipe going to the water heater. Thanks for the information.