Acceptable Reduction in Size for Gravity flow sewer and drain applications
Acceptable Reduction in Size for Gravity flow sewer and drain applications
(OP)
Hello All
We are currently trying to modify the internal couplers on our piping system and one of the solutions is to increase the thickness of the couplers. This will result in a decrease of the pipe OD which will ofcourse have much more effect on the smaller diameters than the larger ones.
If I take the 200 mm pipe for example (ID = 200 mm) what is the maximum reduction that we can make on the joint section so as not to disturb or affect the fluid flow hydraulics. The diameter will return to 200 mm after the joint.
Any help will be much appreciated.
Thanks
We are currently trying to modify the internal couplers on our piping system and one of the solutions is to increase the thickness of the couplers. This will result in a decrease of the pipe OD which will ofcourse have much more effect on the smaller diameters than the larger ones.
If I take the 200 mm pipe for example (ID = 200 mm) what is the maximum reduction that we can make on the joint section so as not to disturb or affect the fluid flow hydraulics. The diameter will return to 200 mm after the joint.
Any help will be much appreciated.
Thanks





RE: Acceptable Reduction in Size for Gravity flow sewer and drain applications
RE: Acceptable Reduction in Size for Gravity flow sewer and drain applications
The question is whether the system will still be adequate for the flow.
There are many ways to analyze the system. For a simple gravity system, try searching wbdg.org for Army Corps methodologies.
If you have an 200mm (8") pipe that is a hundred feet long and reduce the size at one joint by 10%, there is likely no problem hydraulically.
The other issue, which is probably more important, is that if you have a symmetric coupling of a smaller diameter, you are creating a hump in what should be a smooth invert.
RE: Acceptable Reduction in Size for Gravity flow sewer and drain applications
so basically the problem is that sediments could be trapped on the edge of this "hump" if it is large enough. Again, for a 200 mm pipe, what could be this "hump" size that would be just ok?
RE: Acceptable Reduction in Size for Gravity flow sewer and drain applications
RE: Acceptable Reduction in Size for Gravity flow sewer and drain applications
The reduction in size would tend to trap debris, silt, grease, etc. This will lead to material building up over time and causing the fouling and clogging of the sewer.
The coupler should be external not internal.
RE: Acceptable Reduction in Size for Gravity flow sewer and drain applications
No reduction in pipe size along the invert is acceptable.
RE: Acceptable Reduction in Size for Gravity flow sewer and drain applications
Thanks a lot
RE: Acceptable Reduction in Size for Gravity flow sewer and drain applications
RE: Acceptable Reduction in Size for Gravity flow sewer and drain applications
You haven't said why you are doing this. External couplings for HDPE are readily available.
RE: Acceptable Reduction in Size for Gravity flow sewer and drain applications
RE: Acceptable Reduction in Size for Gravity flow sewer and drain applications
Corrugated HDPE is widely used for stormwater applications (although I don't recommend it) and you shouldn't need an internal coupling.
RE: Acceptable Reduction in Size for Gravity flow sewer and drain applications
Richard A. Cornelius, P.E.
WWW.amlinereast.com