PVC sewer lines - where does the slope come from?

[Jim Koepke]

What opportunities are mine as I struggle with great difficulty to understand the meaning of your post?

Especially with today's toilets using a lower volume of water, running the tap while washing one's hands adds a bit more water to help in moving the solid waste along its way.

jtk

[Tom Stenzel]

...As long as the slope is adequate to maintain a velocity of 2 feet per second, the pipe will self cleanse. Pipe laid too flat or with a belly will tend to have a sediment buildup in the invert. Unless you get a grease clog (a big one has been called a fatberg by the press!) or a physical impediment such as a broken pipe or roots, the pipe will self cleanse. "Running water will wash it away". https://www.theepochtimes.com/19-ton...r_2661577.html

Ole has right.

I noticed that the report about the "fatburg" had the line, "From there the waste is supposed to go to a processing plant in Detroit."

Hey wait- that processing plant is where I worked. For 31 years 8 months not that I was counting.

I remember reading a reprint of an article in a wastewater treatment periodical by a Detroit engineer that described large clumps of grease that would come into the plant during rain events and damage the screening equipment. Plus the grit channels would get buried. This led him to develop an interceptor constant velocity strategy that would prevent the buildup of geases and grit in the system.

The engineer was Clyde L. Palmer. The article was published in 1940. I'm sure Mr. Palmer rubbed a digit or two off his slide rule coming up with those graphs. When I wandered into the plant a few decades later that strategy was still in place. Plus weekly pumpdowns where the water level was taken down almost to the point of pump cavitation to scour out the system. Allowing standing water to remain in the collection system to save pumping costs always came to a bad end.

We were expected to deal with whatever grease and trash arrived.

-Tom

[lowell holmes]

See this link

http://www.balkanplumbing.com/pitch-...se-drain-pipe/

[Ron Citerone]

Interesting thread. The more I learn about any profession, the more I understand how much I don't know...........................and how people who often accuse others of "overthinking" things don't know. If that makes sense.

[Jim Koepke]

Interesting thread. The more I learn about any profession, the more I understand how much I don't know...........................and how people who often accuse others of "overthinking" things don't know. If that makes sense.

A great observation Ron.

It is always the know nothings that seem to insist they know it all.

jtk

[Dylan Wyatt]

We just went through this derivation at work last week in an effort to prove we could lay a pipe flatter that minimum grade. The minimum slope of gravity sewer pipe is the minimum slope for solids to stay suspended in the liquid in a gravity sewer pipe, 2 feet/sec. This is based on the pipe flowing full and with a roughness coefficient for concrete (or clay, I can't remember for sure). In our case it is regulated by the EPA. The jury is still out on if they will approve the plans, but with simple calculations we proved that we could lay a PVC Sewer line almost 0.10% flatter than the EPA Book called for, which was critical in our circumstances.

[Bill Jobe]

A great observation Ron.

It is always the know nothings that seem to insist they know it all.

jtk

I thought I was right.
I opoligize.