Need to place a hole in a concrete wall to be poured for a waste pipe serving a toilet in a commercial building. Trying to determine the elevation of the waste pipe when it will exit the building. The run to the sewer connection is long and the sewer connection elevation is shallow. We are trying to avoid the use of a lift station and would like to keep the depth of this run at a minimum. One plumber told us to plan on a 12" straight drop from the floor flange to the waste L then maintain a 1/2" per foot slope to the wall (14 foot run). This slope seems to be excessive. If 4" pipe is used I would think a slope of 1/8 to 1/4 per foot would be enough. Thankyou for any help. This wall needs to be poured and I'm having a heck of a time getting another plumber over to look at this design.
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