Jump to content

Roof area:drain pipe volume/size calculation?

Recommended Posts

I'm helping out a friend, overseeing some work she is having done and the guy putting in the drainage systems is going to run all the gutter drains underground to a public storm drain. The house has a really large roof area and he asked me if I know of a calculation to figure the appropriate pipe size to handle the volume of water that will come off it. I told him, I didn't, but I know where to pose the question with a high probability of getting a good answer.

Any takers?

Link to comment
Share on other sites

Chapter 13 of the National Standard Plumbing code would be his starting point.

Everything is dependent on the area & slope of the roof; once you get underground it depends on the slope of the pipe.

I took a course many, many years ago at NJIT called Hydraulics & Drainage and was actually pretty good at it; but if you asked me today to calculate something, I'd spend more time re-learning what I forgot than figuring out the answer.

Link to comment
Share on other sites

"The size of the roof drain system is based on local rainfall

rates. Both the International Plumbing Code (IPC) and the

Uniform Plumbing Code (UPC) publish rainfall rates. These

rates can be found in Appendix B of the IPC and Appendix D

of the UPC. The rainfall data in the UPC is based on National

Weather Service Technical Paper No. 40, Chart 14: 100-Year

60-Minute Rainfall. The IPC bases its data on “a storm of onehour

duration and a 100-year period,â€

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.


  • Create New...