Inadequate slope new addition drain

[E3 CCook]

I hired a plumber to rough in plumbing for new kitchen and bath. The new drain line that connects the new plumbing to the old is a 3" line with about 1/2" slope in 8ft (1/16" per foot). The new work has not been inspected yet by the local code official. If the code official doesn't flag this, am I going to have long term problems with this minimal slope? Should I specifically ask the code official about it? If I'm not here when they get the work inspected and it's not flagged, do I have any recourse? BTW I'm in an IPC jurisdiction.

 

[seann]

did you use a tape measure to check the slope? Try putting a level on the pipe to see if it has any slope. if you haven't already. Just in case what your measuring off of with your tape is not level. If your bubble is just breaking the line showing that you have slope, your ok in my opinion. I doubt the inspector will check to see if the pipe has slope. At least they don't in my city unless it is visually obvious that it is completely flat of flowing backwards. The inspector just looks at it quickly to see if it is plumbed correctly as far as pipe size and venting goes. My city will allow 1/8" a foot of fall if space is limited and that drains fine. If yours is 1/16" a foot as you say, it could potentially create an issue with drainage. I wouldn't trust your tape measure though. Use a level. If you still think it is flat after that then maybe call the plumbing company first and tell them to come look at it again, before the inspection. They would much rather fix it for you now if it was an oversight on their part, then to fail an inspection and have to come fix it.

 

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[E3 CCook]

did you use a tape measure to check the slope? Try putting a level on the pipe to see if it has any slope. if you haven't already. Just in case what your measuring off of with your tape is not level. If your bubble is just breaking the line showing that you have slope, your ok in my opinion. I doubt the inspector will check to see if the pipe has slope. At least they don't in my city unless it is visually obvious that it is completely flat of flowing backwards. The inspector just looks at it quickly to see if it is plumbed correctly as far as pipe size and venting goes. My city will allow 1/8" a foot of fall if space is limited and that drains fine. If yours is 1/16" a foot as you say, it could potentially create an issue with drainage. I wouldn't trust your tape measure though. Use a level. If you still think it is flat after that then maybe call the plumbing company first and tell them to come look at it again, before the inspection. They would much rather fix it for you now if it was an oversight on their part, then to fail an inspection and have to come fix it.

- Thanks Seann. I used a bubble level and laser level to check bottom of joist and it's dead level. Then I measured the height of 2 power bar supports they installed that are 52 in apart and the diff between the 2 from joist bottom is 1/4". The bars are installed level. I also put a short bubble level on the underneath side of the 3" pipe and the bubble is about 1/2 way to the 1/8 mark (not breaking the 1/8 line). All adds up to 1/16 slope.

Good idea on pointing it out to the plumber. Part of the irony is it's a long run with tight clearances in the bay where the 3" line runs and I measured it for 1/8 slope. The plumber told me it had to be 1/4 even tho we're in an IPC jurisdiction. I think he ran the first 8' at 1/4 then realized there wasn't enough height in the bay to continue so he reduced the slope sharply for the next 8'.

 

[seann]

Yes I can see that happening. Sometimes there just isn't enough room in tight spaces to get the optimal amount amount of slope. I'm sure if he would have realized ahead of time he would have just done an 1/8" on all of it. These are the times when the inspector will allow for a variance from code. Such as when I said they will allow 1/8" of slope if there is no room for 1/4". It happens a lot on remodels and happens on new construction also on long runs. It's one of those things that most homeowners wouldn't think to check for. And In all honesty if you hadn't checked your slope and just went with what has been installed you most likely would have never had an issue with it plugging up. But you never know, especially with the low flow toilet now a days not having as much water to push things down line.
I've seen people with drain lines in their homes that are sloping backwards and have been that way for years with no issues coming from it, but others do. A "short" section of new PVC with a flat slope isn't the worst thing in the world . Its when it is a long run or sloping backwards that issues will typically start to arise. Mainly because heavier deposits can settle and start to accumulate in a pipe with backwards slope, which will eventually lead to a clogged drain in most cases. Unlikely to occur on a flat line of PVC pipe that is a shorter run such as yours in my opinion. I'm not condoning it, just giving some perspective from my experience. It's always best to do it right if possible. And it may be as simple as adjust a couple of hangers in your situation. Best of luck!

 

[Michael Young]

I hired a plumber to rough in plumbing for new kitchen and bath. The new drain line that connects the new plumbing to the old is a 3" line with about 1/2" slope in 8ft (1/16" per foot). The new work has not been inspected yet by the local code official. If the code official doesn't flag this, am I going to have long term problems with this minimal slope? Should I specifically ask the code official about it? If I'm not here when they get the work inspected and it's not flagged, do I have any recourse? BTW I'm in an IPC jurisdiction.

Yes. It will work. But the minimum slope should be 1/8" per foot. What will it take to get the proper slope on your pipe. Call your plumber and have him fix it.