Is 1/4" drop in 10' enough.

[John White]

I plan on putting underground pipe to capture water run off on the roof of my building. It will be using smooth pipe. In a 80' run how much drop would I need? I usually like to have 1" in drop in 10'. But am sort of limited in this case.

 

[LD1]

I think 1/4" is fine. With smooth pipe, any drop at all and water will flow. But it is really hard to be that accurate when trenching in pipe...

 

[radioman]

I use a 4 ft level and make the bubble on one side of the center and its more then enough to make sure its flowing downhill. I don't measure via inches . just a level.

 

[wolftree]

Tape a pencil crosswise on the downhill side of your level to give you a 1/4 inch by whatever length your level is.

 

[LD1]

Tape a pencil crosswise on the downhill side of your level to give you a 1/4 inch by whatever length your level is.

Unless he has a 10' level, that wont be enough for what he is wanting

 

[greasemonkeyok]

I plan on putting underground pipe to capture water run off on the roof of my building. It will be using smooth pipe. In a 80' run how much drop would I need? I usually like to have 1" in drop in 10'. But am sort of limited in this case.

The rule of thumb I am familiar with is 1/4" per foot. But it actually depends on the amount of water that will be drained to be precise. A more involved answer can be found here:
What is the recommended slope for drain pipe carrying excess rain water from pool and deck around pool

 

[MacLawn]

Grease, that link only took me to the question. Anyway, I've always kind of leaned to the 1/4" per 10' system. I know volume will make a difference, and pipe size. John White, how big is ye pipe? For 80', 4" pipe might be a tad small, but I don't know. I'd feel better with maybe 8" for that length. I actually need to do something very similar for runoff from me house, but only have about 40' to go.

 

[greasemonkeyok]

Grease, that link only took me to the question. Anyway, I've always kind of leaned to the 1/4" per 10' system. I know volume will make a difference, and pipe size. John White, how big is ye pipe? For 80', 4" pipe might be a tad small, but I don't know. I'd feel better with maybe 8" for that length. I actually need to do something very similar for runoff from me house, but only have about 40' to go.

I get the answer below the question on that link, which refers to Table 1106.3 "Size of Horizontal Storm Drainage Piping" from the International Plumbing Code.

If you have commercial experience then you way ahead of me, my experience is limited to doing my own drains.

 

[RickB]

Unless he has a 10' level, that wont be enough for what he is wanting

Actually, it will be more than what he is wanting. But I'd want no less than 1" in 10' of run myself. 1/4" in 10' won't eliminate low spots in a trench.

 

[LD1]

Actually, it will be more than what he is wanting. But I'd want no less than 1" in 10' of run myself. 1/4" in 10' won't eliminate low spots in a trench.

Thanks for the correction. My fingers and brain werent on the same page. Happens sometimes