I have a 3" Septic line that is under neath the floor joists and needs to get to a 5" chase in the Foundation. Its about a 2' elevation difference from the 1/4" foot run elevation and the chase.
Then from the Chase to the Septic Tank I need to again do a rapid decent from the chase to the level that will give me 1/4" foot out to the Septic Tank.
So my question is this, do I do a Right 90 down in elevation, and 90 over or do I do a 45 and 45?
Seems like the 45/45 is the way to go, but I don't want my liquids to run away from my solids. In keeping with the theory of a multi story house. its all 90/90 to get from floor to floor.
There is such a thing as minimum slopes for sewage lines, but not a maximum slope. The more slope, the better. The liquids running away from solids and causing clogs theory is a myth. High flow velocity is good. See this:
Vertical lines are used all over the place, between floors and down to the basement floor for sewer and drain lines. If you have the space you could use two 60 degree ells as they take less room than two 45 degree ells. If you don't have or want to use the space you can use two 90 degree ells, however you may want the bottom one replaced by a wye topped with a 45 to achieve 90 degrees with a clean out in the other inside end.
Jim, kindly re-read my post. 45-45 is what I was advocating since I explained that the OP doesn't need to worry about a 45 slope leaving solids behind and causing clogs.
Jim, just out of curiosity: Have you ever run across a situation where clogs were occurring due to excessive slope? I ask this because there are those in sewer maintence that have said that excessive slope has never been a problem with causing clogs. And the study I cited noted that sediment is less likely to form with increased slope.
In common household sewage lines, you often have lines going from horizontal to vertical, which would cause the liquids to drop away pretty quickly, if anything would, but yet solids collecting in the region before the vertical drop and causing clogs doesn't seem to be an issue.
In hopes of putting this myth to rest once and for all, I found another article specifically on the subject from Plumbing & Mechanical Magazine. Here's an excerpt from a Google cache of the article:
*** Lessons Learned
One of my favorite stories about George occurred at a Plumbing Exposition. George was on the Board of Directors of the ASPE Research Foundation. He helped set up a demonstration model for the show. The model had four of these new fandagled 1.6-gpf water closets. There was a 3-inch drain line in clear plastic pipe. (Installed by a UA contractor, of course.) The model had different segments of pipe to demonstrate different flow parameters. One section of pipe was pitched about 3 inches per foot.
As the show was about to begin, George was speaking to a few of us standing around. He looked at this steeply pitched pipe and said, "We might have a problem with stoppages in this section of pipe. I'm afraid the liquid will be running away from the solids." I just smiled.
As the demonstration began, they flushed carrots, beets and peas. When the vegetables hit the steep section of pipe, they took off down the pipe, flying at a high speed. George looked over at me and said, "Well, I'll be. You knew that was going to happen, didn't you? You see, my apprenticeship instructor always taught us that if you pitched the pipe too much, the liquids would run away from the solids." I said to George, "My plumbing instructor said the same thing, but my engineering professor explained why this is a plumbing myth and would never happen." For the next hour we spoke about engineering principles. Here George was in his 70s learning new concepts so he could relay the information to others.
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