Maximum slope for sewer -- handling a vertical step or drop under CPC/UPC

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I'm trying to find in the UPC the right section to deal with a step or drop in a standard 4" sewer line, where the usual 1/4" per foot can't be maintained. I'm aware that making the entire line sloped steeper can cause problems with solids, but that a drop can solve the problem.

What's the best way to handle this? Does code cover this situation?
What are the maximum and minimum slopes for each section?
 

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wwhitney

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I'm aware that making the entire line sloped steeper can cause problems with solids, but that a drop can solve the problem.
I have heard that but I wonder if it is really true.

UPC is silent to my knowledge, minimum slope is 1/8" per foot for 4" drains/sewer, maximum is infinite (vertical).

Cheers, Wayne
 

John Gayewski

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There is a max slope for different configurations. Such as a combination drain and vent system has a 1" per 1'slope max. Other than that there isn't a max.

I personally have dug up many of sewer with crazy steep pitch on them. Our sewers locally are between 8 and 16 feet deep in the street. Most of the laterals serving houses are between 4 and 7 feet deep. That makes for some very steep drops down into the city sewer. The only consistent problems we have are with clay pipe and roots. I've never actually laid my eyes on a sewer that was ran too steep and caused a problem. We did replace some 1.6gpf toilets with 1.28gpf toilets that caused backups. The only thing we could figure was the combination of low flow, old sewer, and a 45 vertical offset. Those things in combination were causing backups. All we did was change from a tower flush valve to a 3"flapper. For whatever reason that stopped the backups. But my opinion generally is that a max sewer slope is an old plumbers tale.
 

Jeff H Young

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There is a max slope for different configurations. Such as a combination drain and vent system has a 1" per 1'slope max. Other than that there isn't a max.

I personally have dug up many of sewer with crazy steep pitch on them. Our sewers locally are between 8 and 16 feet deep in the street. Most of the laterals serving houses are between 4 and 7 feet deep. That makes for some very steep drops down into the city sewer. The only consistent problems we have are with clay pipe and roots. I've never actually laid my eyes on a sewer that was ran too steep and caused a problem. We did replace some 1.6gpf toilets with 1.28gpf toilets that caused backups. The only thing we could figure was the combination of low flow, old sewer, and a 45 vertical offset. Those things in combination were causing backups. All we did was change from a tower flush valve to a 3"flapper. For whatever reason that stopped the backups. But my opinion generally is that a max sewer slope is an old plumbers tale.
been aware of the controversy But I've never bought into this excessive grade , I think the story makes some sense but , if I'm running down hill I let r rip. I'd just follow code I prefer 1/4 inch minimum on 4 inch and really don't run bigger pipe than 4 on my jobs unless I'm working for another contractor.
Might be a concern on very long runs, If I was running 100 foot and diving down 20 foot I might worry a bit , I haven't had one I was concerned about yet.
Let us know how you decide to address it?
 

Sylvan

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The too much slope leaving solids behind I found not to be true BUT when the sewers were sized by fixture units (7.48 gallons) no one at that time knew about toilets with 1.6 GPF so scouring action was severely reduced

Ferrous and non ferrous metals can fail from excessive velocity, plastic systems are more immune from this type of failure


 
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