Steep hills & Sewer lines

[ChrisInVan]

I was not able to find much information online on how to deal with steep hills and running sewer lines down a hill. I understand you don’t want to exceed your 1/4in per foot slope. What are alternatives? Are U bends or zigzag acceptable? Are 180 degree on a 3in or 4in sewer line acceptable at all? What about plumbing the main sewer line like vertical steps? Is that acceptable considering clean outs and of course thinking about 1/4in per foot slope for every step? Any guidance would be appreciated.

 

[Jadnashua]

The slope, I think, is listed as a minimum...not sure if there really is a maximum. Consider that in a home, it's often vertical. What you don't want is to try to make it go uphill! In the main system out by the street, when that happens, they use a pump.

I'm open to learn, if I'm mistaken!

 

[Sponsor]

 

[ChrisInVan]

The slope, I think, is listed as a minimum...not sure if there really is a maximum. Consider that in a home, it's often vertical. What you don't want is to try to make it go uphill! In the main system out by the street, when that happens, they use a pump.

I'm open to learn, if I'm mistaken!

Thanks for your response. I was under the impression that if you have too much slope, liquids will travel faster than solids so you will end up with a clog?

 

[Jadnashua]

Even with 1/4" per foot, because of friction, the solids may stop along the way and the next burst of water pushes them along a bit further.

In a home, anything 45-degrees or over is considered vertical.

I'm not a plumber but I don't remember anything in the code that specifies excess slope in a drain line, but then, I've not read the whole thing!

 

[ChrisInVan]

Even with 1/4" per foot, because of friction, the solids may stop along the way and the next burst of water pushes them along a bit further.

In a home, anything 45-degrees or over is considered vertical.

I'm not a plumber but I don't remember anything in the code that specifies excess slope in a drain line, but then, I've not read the whole thing!

Thanks- so what you are saying is as long as I am 45 degrees or more slope it is considered a vertical drop and safe? Thank you!

 

[Jadnashua]

Thanks- so what you are saying is as long as I am 45 degrees or more slope it is considered a vertical drop and safe? Thank you!

Not exactly...in a home, they consider anything over 45-degrees to be vertical when it comes to things like venting requirements. There's often some vertical drain lines in a home as well that aren't any problem. On a long run, I'm not aware of any code issue that says there is a maximum slope, only a minimum, but then, I haven't scoured the codes to verify that.

 

[Mr tee]

There are codes on minimum grade, but not on maximum.

 

[Jeff H Young]

Good Topic, Jadnashua noticed same thing I have. its 1/4 inch minimum and in the real world pipe isnt perfectly straight so if you stride for minimum grade your going to have spots that dont meet that minimum. so on long runs I put extra on it always if possible because if inspector puts level on one spot .
Ive been hearing the tale of liquids out running solids my whole career , I only guess there is some truth to it. I dont know what the sewer company does when they go up a hill 100 feet but I can tell you the sewer aint going to be 75 foot deep.
On a 100 foot run out from my house , 25 inch of fall is standard I would rather have 50inches than 12.5 inch and on 4 inch 1/8th inch is allowed. Thats just me I could be wrong.
I have just a small amount of trust in codes and standards of construction and I belive if it made all that differance that they would put a maximum in somewhere. Is it screw up that no one ever thought of maximum fall ? I think not its a question and argument been going on my short time in the buisness. We have all contemplated this I say dont worry about it

 

[Sylvan]

The old tale was to much slope would cause excessive velocity and cause erosion

So figuring the velocity is excessive then every sewer ejector /sump pump will need their dischage pipe replaced often (did not happen)

The olther school of thought was water travels faster then solids thus leaving solids behind to cause stoppages

This was proven to be not true when old plumbing systems were sized by fixture units (7.48 gallons per) and then the old 3.5 toilets were replaced with 1.6 or 1.3 GPF and everyone thought there would not be enough scuring action or enough GPM flow to keep solids suspened

When we installed 8" sanitary lines in buildings the min pitch we could use was 1/16 per inch which allowed us to have 1440 FU's BUT if we increased the pitch to a 1/2" per ft we could increase the FU's to 2300

On the vertical waste or sanitary stack 6992 FU 's (53,300 GPM)

 

[Sylvan]

Required velocities at design flow (Q) for sewer pipelines shall be minimum 2 fps and maximum 10 fps. The maximum velocity at design flow allowed in any sewer pipeline is 10 fps.