I learned here that 1/4" per foot for pipe is just about perfect.

But the plumbing code says that you can use 1/8" per foot for 4" pipe. Your thoughts?

I have a sewer job coming up that is a long run. I'm planning on using 4" PVC. It is for a new home. The city designed the sewer run.

Once outside the house the line is 100' downhill. Then it turns about 100 degrees and flows downhill another 132'.

At this point the city will pick up the sewer line, shoot it under the road and connect it way down the hill to the city sewer.



I'm worried about using 1/8" per foot because I don't want call backs for repeated blockages. And, I don't want to re-do this and have to bury the line deeper at a steeper angle.

And, I'm worried about using 1/4" per foot because I will be at least 13' deep when I get to the street.

I am aware that the house, which has yet to be built on the empty lot, faces another street. But, the city says that road (Shelburne Dr) does not have city sewer.

I am exploring other ideas, but for now I am focusing on finding out the pros and cons of the city's suggestion.



Edited 6 times.

can you do 3/16 per foot ?

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"Measure Twice & Cut Once" - Retired U.A. Local 1 & 638

The Roman aqueducts were sloped roughly 1” per 1,000’

The code says 1/8” is fine then it’s fine plumbing engineers have worked vigorously on the slope per diameter of piping

I doubt it. North Carolina plumbing code says 1/8" per foot is the minimum.

Thanks! You gave me an idea I had not really considered. I can go up in diameter to 6-8" and have less pipe slope--that may be an option.



Edited 1 times.

The Roman aqueducts handled clear potable water only.

==============================================

"Measure Twice & Cut Once" - Retired U.A. Local 1 & 638

Ionce installed a 600+ ft. 4" clay tile sewer at less than 1/16" grade and as far as I know, it never had a problem. But a 230' sewer would NOT have 13' of fall at 1/4" pitch.

4.791666666666667 feet of fall to be overly precise


230' at 1/4" per foot = 57.5 total " / 12 = above


HOWEVER


Apparently the entire 'run' is downhill from the house ... soooo ... the pipe may not need to be pitched relative to the trench at all.

==============================================

"Measure Twice & Cut Once" - Retired U.A. Local 1 & 638



Edited 1 times.

You are correct.

I forgot to mention that I only included the 132' foot portion at 1/4" per foot (33" drop), not the initial 100'.

And, I also forgot to note that there is a hill next to the home that does not show up well on the map I posted.

The pipe burrows into the side of the hill (that the house sits on) before it gets to the road.

When you add in the soil depth of the hill plus the 1/4" per foot drop the pipe is 13' deep at the road.



Edited 2 times.

What's the depth that the City can work with at the road?

Re-reading your original description states the first 100 feet is downhill and the 132 feet is also downhill. What's the elevation difference between the building site and the road you are stopping at?