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Maximum Slope for sewer PVC pipes 8 in and above

Maximum Slope for sewer PVC pipes 8 in and above

Maximum Slope for sewer PVC pipes 8 in and above

(OP)
Good Day,

Is there a maximum slope for sewer pipes? I could only find the minumum slope for each pipe sizes in the 10 state standards.
I am looking for an information resources that states that there is a maximum slope that will leave the solids behind if the water moves to fast , or
if I am wrong I am open to correction for my assumption.

sorry for the confusion.

RE: Maximum Slope for sewer PVC pipes 8 in and above

I seem to remember a standard that sewer pipe flows are supposed to be between 2 and 15 feet per second. At least 2 fps to keep solids from getting stuck in the pipe, and no more than 15 fps to prevent damage to the pipe connections and system.

RE: Maximum Slope for sewer PVC pipes 8 in and above

I'm not a piping guy (binary term for PC)... The higher velocities may cause cavitation. Can this be a problem with PVC piping?

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

RE: Maximum Slope for sewer PVC pipes 8 in and above

Given the fact that PVC is installed vertically inside buildings for both sanitary and storm, I don't think the pipe is the issue. Bedding and/or associated installation parameters might.

RE: Maximum Slope for sewer PVC pipes 8 in and above

Now that I think of it, there are also the vertical sections of pipe down the side of deep drop manholes. I don't recall if there is a limit to how far you are allowed to drop sewage vertically.

RE: Maximum Slope for sewer PVC pipes 8 in and above

Inside buildings, there is no limit other than the building height. Just gets complicated as descending flow can create both positive and negative pressure surges which have to be accommodated. Assume it is similar in exterior flow networks.

RE: Maximum Slope for sewer PVC pipes 8 in and above

Like dik, I'm a structural pud, but we had some steep pipe runs in Albuquerque and it caused some problems. I think there were odors (that sewage rocketing down the pipe got all churned up) or pipe wear. We had to install vortex manholes to kill some of the energy/velocity.
As far as restricting velocities, 15 fps seems pretty fast. We never try to go above 10 fps and even try to stay lower.

RE: Maximum Slope for sewer PVC pipes 8 in and above

Maximum grade is generally 15% for 8" and decreases to 4% for a 24". Hydraulic jump and restricted flow can be a concern for steep installations. You are correct that there are vertical sections in outside or inside drop manholes, but they are effectively vented and an emergency overflow is included for a proper installation.

RE: Maximum Slope for sewer PVC pipes 8 in and above

You can go steeper if you want, but it will be costly:

f) High Velocity Protection

Where velocities greater than 15 feet per second are attained, the special provisions described in subsection (c)(4) shall be made to protect against displacement by erosion and shock.

4) Steep Slope Protection
Sewers on 20 percent slope or greater shall be anchored securely with concrete anchors or equal, spaced as follows:

A) Not over 36 feet center to center on grades 20 percent and up to 35 percent.

B) Not over 24 feet center to center on grades 35 percent and up to 50 percent.

C) Not over 16 feet center to center on grades 50 percent and over.

RE: Maximum Slope for sewer PVC pipes 8 in and above

Quote (Penpendrum

Is there a maximum slope for sewer pipes? I could only find the minimum slope for each pipe sizes in the 10 state standards.
I am looking for an information resources that states that there is a maximum slope that will leave the solids behind if the water moves to fast , or
if I am wrong I am open to correction for my assumption.)



My points ;

- Yes there is maximum slope for sewer pipes and changes acc. to pipe material to avoid erosion .

- Minimum slope is slected to provide self cleaning velocity ( 0.6 m/sec ) and free from pipe material








Don't underestimate a nail. A nail saves a horseshoe, a horseshoe saves a horse, a horse saves a commander, a commander saves an army, an army saves a whole country.. GENGHIS KHAN

RE: Maximum Slope for sewer PVC pipes 8 in and above

high velocities and changes from steep to flat create hyd jumps that release H2S (if there is a risk of this in the network). I did a network a while back where some steep sections followed by flat sections was unavoidable due to the terrain, but we ended up adjusting the grade over 3 sections rather than jus one change. was the bottom end of what will become a very large development

RE: Maximum Slope for sewer PVC pipes 8 in and above

(OP)
Good day to you all,

Can I ask what USA references did you get those maximum velocities? Its been a great help guys

RE: Maximum Slope for sewer PVC pipes 8 in and above

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