slope of soil pipes
slope of soil pipes
(OP)
What is the minimum slope required for 8 inch dia soil drainage pipes
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RE: slope of soil pipes
Could you provide a bit more background information? What are the pipes being used for? Foundation drainage? Infiltration tench? How much conveyance do you need? etc
You may not need a"minimum slope depending on the application.
RE: slope of soil pipes
The site conditions do not allow more than 0.7 % slope for this pipe, and since this is less than the recommended minimum of 1 %, our concern is whether the .7% will generate enough velocity for the needed scouring action to avoid any soil buildup in the pipe. The pipe is expected to be half full in the usual case but in the event of peak flow would run 100 % full.
Thanks and Regards
RE: slope of soil pipes
I'd check local design regulations for additional guidance. Hope this helps.
RE: slope of soil pipes
We are about to lay drainage pipe in our project where the trench has been excavated and the pipe bedding is all ready. Above this pipe path there will be a road running above longitudinally above the pipe path and the cover above the pipe will be less than 3 feet. The attached sketch details how to install drainage pipe passing under the road with less that 3 feet of cover. It shows the pipe inside another pipe (sleeve) that is totally encased in concrete. The detail asks for the sleeve to be one diameter larger than the pipe.
1) We are unsure about the empty space that would result between the pipe and sleeve. Furthermore, the pipe material is PVC with bell and spigot joints.
2) The precise benefit of the sleeve is not clear since the sleeve would be totally encased in concrete, and there is no likelihood of the cyclic load (from traffic) effecting the pipe that would be encased in concrete.
3) Since the detail calls for the sleeve, we cannot cancel it out but need to know the best way of doing it along the length of pipe and at the locations of bell & spigot joints.
Your kind feedback in this matter will be greatly appreciated.
Thanks and regards
RE: slope of soil pipes
RE: slope of soil pipes
The maximum slope that is possible on our site is 0.7% and this is fine for 8 inch diameter pipes . However, 0.7% slope is not permissible for 4 inch diameter pipes, so can we simply substitute the 4 inch diameter pipes with 8 inch diameter pipes to come within the recommendation.
RE: slope of soil pipes
If you start changing stuff around without the engineer's permission, and then can't pull your CO because the engineer won't sign off on the as-builts, you're going to have a hard time explaining what the "Eng-Tips Forums" are to your owner.
Hydrology, Drainage Analysis, Flood Studies, and Complex Stormwater Litigation for Atlanta and the South East - http://www.campbellcivil.com
RE: slope of soil pipes
RE: slope of soil pipes
RE: slope of soil pipes
You later mention substituting 8" for 4" to meet minimum slope criteria. I've seen this often done for services (actually 6"/1% versus 4"/2%). I agree this would just slightly slow velocities, but sometimes that's the only way to get a reasonable design solution through agency reviews.
RE: slope of soil pipes
Putting 0.19 cfs in an 8 inch pipe at .7% slope may not provide the necessary minimum velocity you need. Depth of flow will be just over 2 inches and velocity approximately 2 fps.
Now, assuming the sewer was designed for only half full (in the 4 inch pipe), your depth of flow and velocity in a flattened 8 inch sewer would be even less.
Again, this should be an RFI to the project engineer but don't expect it to be approved.
RE: slope of soil pipes
The main run of this PVC pipe in question is collecting sewage from various buildings of the hospital and is being laid from manhole to manhole that will be cast in situ along with this pipe. The joints are bell and spigot type. The manholes are square or rectangular. Complete 6 meter long pipe pieces are being used and there are no stub pieces in the inlet and outlet of manholes.
Furthermore, the manholes are without any sleeves as the pipe will be in place prior to the casting. In other words this main pipe is running through steel rebars of manholes and so will become integral with the manholes. This will preclude the need of grouting between pipes and sleeves (had the latter been placed in the manholes).
Feedback regarding the technical soundness of this method will also be much appreciated.
RE: slope of soil pipes
RE: slope of soil pipes
As a mechanical engineer called in to install drainage pipes (with gravity flow in which the pipes might be half full !), the formula(s) to determine the velocity for a given GPM would be most helpful. A sample calculation for any GPM would be a valuable guideline (the pipe material is uPVC), as well as how to determine the fullness status of pipes (half full, etc.). Thanking you in advance.
RE: slope of soil pipes
http://www.lmnoeng.com/index.shtml
Mannings equation is only valid for free flowing conditions, this equation is no longer vaild under pressurized flows.
I think this has been hinted at in the previous posts but most engineering standards require minimum sizes of sewer to be 8-10" especially for commercial and industrial applications.
Hope this helps.
RE: slope of soil pipes
I respectfully disagree with cvg, who is very knowledgeable, concerning his posts above on 27/08/10 1:04 and 12:09. Ten States clearly states that the minimum sewer velocity (slope) is based on the pipe flowing full. A 1% slope on an 8" pipe is not required by code, at least according to Ten States, which has been adopted by Florida and Georgia in which I practice and I believe by at leat 40 other states. Obviously there are situations in which the standard minimum regulations should be exceeded, but I don't see anything special in this situation as described.
RE: slope of soil pipes