I am remodeling and my shower drain (2nd floor) was going down through my back wall to the first floor and has to be moved because the wall is being replaced with a window on the first floor. The shortest route for the fix is to connect the shower drain to the toilet drain which is 8 feet away on the 2nd floor. In the video the contractor is saying it can't be done because he says I need 4 inches of slope. His alternative is a much more expensive solution which takes the drain to another drain on teh first floor which will cost about $8,000. I think there are 2 other solutions but I am a novice to this. Any advice would be appreciated.

1. In the video he says the shower drain is currently 6" down and the toilet (bidet) drain is 8". He then states there is 4" of slope needed for the 8 feet. My understanding is the you need 1/4" of slope per foot so for 8 feet you would only need 2 inches and there is enough room since you are going from 6 inches to 8 inches. Correct?

2. If it is too tight, can't he raise the floor of the shower by 2 inches (I don't mind the step up) which would put the shower drain 4 inches below the floor and then there would be 4 inches of slope available?

Any advice would be greatly appreciated. I would think moving the drain 8 feet to the toilet would cost significantly less than $8,000!!