I have a 4" (inside diameter) cast iron drain pipe that is clogged (very slow to drain). I tried cleaning it with 20' of 1/2" cable ... no success. I estimate the clog is about 50' down the drain (I let the pipe drain for 24 hours, then filled it up quickly and measured the volume of water and pipe to estimate where the clog is).

I went to my local tool rental shop and the only thing they have is a heavy duty drain cleaner with 100' of 3/4" cable. The guy said 3/4" cable is good for pipes between 3" and 6".

Is 3/4" cable too big for a 4" pipe?

Another problem is that the closest I can get the machine to clean-out point is about 5'. I know it is best to get as close as possible. Is 5' too dangerous?

Thanks for any advice.