Here is a filament rack i designed myself. You can see it in the picture and has been working well for over 2 years now. My recommendation is to print a bottom, then a short 2 or so inch conduit to the first middle rack that will actually be the first layer that can hold that way your filament isn't standing on the floor like mine kinda is in the picture.
If you want to make sure the print is accurate for your exact EMT conduit that's what the test piece is for. You want it snug. Gravity and friction holds it together well.
I recommend PETG or ABS though I printed in sunlu PLA+ and its worked well for 2 years.
Enjoy.
The author marked this model as their own original creation.