Waste pipe slope question... about 150' run

[jetranger]

Hoping there may be some builders or plumbers that can help with my question...

Most search results I've found have more to do with drain pipe slope inside of a building, but they don't really talk about different situations in regards to the slope of the terrain from the building to the sewer tie-in.

My shop is about 150' from the street, and where my house sewer tie-in is located. The first 100' or so, it will be easy for me to accomplish the 1/4" per foot slope, but the last 50' or so, the terrain is much more sloped. I believe the slope will be closer to 1-2" per foot if I followed the relative slope of the terrain.

My question - do I stick with the 1/4" per foot, then go straight vertical down for a few feet, then continue the 1/4 again (almost like stair stepping down)? Or do I increase the slope of the drain pipe overall?

Thank you GJ!!

 

[Toomanytools?]

If is is a black water waste pipe follow the 1/4" rule. If you have to dig deeper in that last 50' to maintain that slope. If your slope in too great 1-2" then the water runs faster than the solids which get left behind and can build up.

 

[jetranger]

Yes, it is black water.

What do houses on very sloped lots typically to? For example - a house built into a mountain where it's a 6" drop per foot to get to the sewer? Do they do vertical sections every so often?

Thank you for your help!

 

[Pluribus]

Had a septic system designed for a difficult lot I used to own. Septic designer was highly recommended by multiple people and did a lot of business. At one point I asked him about locating the septic system at the bottom of a very steep hill, approximately 35% slope average with over 100' of elevation drop. Keep in mind that it would be the septic tank and drainfield, not just the drainfield. In other words, solids would be making the trip. He explained to me that the whole "liquids outrunning the solids" thing was...well, ****.

Quick internet search yielded this:
https://www.pmmag.com/articles/87363-it-s-the-solids-that-run-away-br-julius-ballanco

 

[Garagefffreak]

I believe that you should consult someone that is a professional in the field. The solids may or may not remain behind if you make a bigger slope than recommended. There are many factors that can influence that.

What is the average temperature in the soil in your part of the country where you live? Rethorical question. You cant know that for sure but it can influence it. Image in it gets cold during the winter (obviously it can't freeze the contents of the drain pipe, they are burried beneath the freezing temp) but it can reduce their ability to flow. There could be other factors that can influence the whole thing. Best to consult with an expert.

 

[mcbane]

Hoping there may be some builders or plumbers that can help with my question...



Most search results I've found have more to do with drain pipe slope inside of a building, but they don't really talk about different situations in regards to the slope of the terrain from the building to the sewer tie-in.



My shop is about 150' from the street, and where my house sewer tie-in is located. The first 100' or so, it will be easy for me to accomplish the 1/4" per foot slope, but the last 50' or so, the terrain is much more sloped. I believe the slope will be closer to 1-2" per foot if I followed the relative slope of the terrain.



My question - do I stick with the 1/4" per foot, then go straight vertical down for a few feet, then continue the 1/4 again (almost like stair stepping down)? Or do I increase the slope of the drain pipe overall?



Thank you GJ!!

Not a sanitation engineer but I believe a century ago engineers worried about steep slopes causing excessive velocity and associated erosion in drain pipes. The design goal was to keep water velocity under 10 ft/sec. I suspect that was due to unfired clay and weaker concrete pipe, rather than a concern about sewer salmons being beached.

Modern sewers don’t have as much sand and gravel in the flow and the newer pipe materials are much less susceptible to erosion.



Sent from my iPhone using The Garage Journal mobile app

 

[karoc]

From what I understand its 1/4 per ft. If the pipe is slop to much the water will move to fast and leave the solids behind. I'm not a plumber but I work with few in main. dept

 

[Retroman]

Not a plumber but a sawcutting and demo estimator and I read on a lot of plumbing plans for 4" or larger sewer piping 1/8" per foot under 4" they can go up to a 1/4" typically plumbers out here run the required slope and then drop the last few feet at a 45% angle to get the right elevation to make the tie in point.

 

[tom-ky]

I am not a plumber but stating what I did. I did the 1/4" per foot as far as I could which was a few feet from the building. Septic is probably 40-50 feet away, can't recall for sure but it probably drops 2 feet in that distance. 3 years and no issues yet, I know I haven't put a lot of solids in it put my wife has but probably not much.

 

[59 wagon man]

with that kind of run you WILL have problems. i have a few accounts with runs like that and they have problems no matter what is done. about a 150' run straight cast iron no hub and then it makes a 90 degree turn and we have a problem. only so much a 1-1/4 gal flush will carry and change direction. i would suggest a cleanout every 75ft or change of direction of 90 degrees

ps- i did lots of homes in nj and we followed the slope of the hill
pps- numerous times we have located a sewer line maintaining a 1/8" pitch and got to the sewer connection and there is an 18' to 24" vertical drop to hit the sewer. Why do i know? cause the owner complained of numerous backups and the long horizontal run with minimum pitch didn't work, also realize these buildings were built pre 1990 when we had 3.5 to 5 gals per flush

 

[coldh2o]

Had a septic system designed for a difficult lot I used to own. Septic designer was highly recommended by multiple people and did a lot of business. At one point I asked him about locating the septic system at the bottom of a very steep hill, approximately 35% slope average with over 100' of elevation drop. Keep in mind that it would be the septic tank and drainfield, not just the drainfield. In other words, solids would be making the trip. He explained to me that the whole "liquids outrunning the solids" thing was...well, ****.

Quick internet search yielded this:
https://www.pmmag.com/articles/87363-it-s-the-solids-that-run-away-br-julius-ballanco

This is correct, you'll have no problem with a slope of 1-2"/foot.

The advice for cleanouts is also sound, at every change in direction or a maximum of 50'.

 

[larry4406]

Not a plumber but a sawcutting and demo estimator and I read on a lot of plumbing plans for 4" or larger sewer piping 1/8" per foot under 4" they can go up to a 1/4" typically plumbers out here run the required slope and then drop the last few feet at a 45% angle to get the right elevation to make the tie in point.

This is what the plumbers in my area do.

 

[kj_mustang]

My system was installed with pvc pipe about 8 years ago. My building is about 200' away from my septic tank that is only in the ground about 6-8". The tank site is at least 10' lower than my building with most of the elevation change over about 20-30' of that distance. My line is about 4' in the ground when it comes into my building to my main drain stack so I would suspect the slope is maintained pretty well. Cleanout required here about ever 60 feet.

 

[Innovate1]

Not sure what the best way is but can only say that I plumbed a house where the sewer connection was pretty deep and the minimum depth of plumbing was 12" as I recall due to only light freezes there. I came out of the house just under the footing at the normal slope of 1/8-1/4" per foot and then did a much steeper run to get to the sewer stub out. It wasn't 45 degrees. Probably more like 20 - 30 degrees. Used a 45 at each end of the slope to get things lined up. Was told by the inspector that it looked great. Never had any trouble with it but the run was short - it was just on a small city lot.

 

[glentre]

My father was a plumber all his life. He always said that the only thing you need to know to be a plumber is that **** runs down hill and paydays are on Friday. Violate any of these two and you are in trouble.

Glen

 

[Loose Nut Buster]

Had to replace my clay tile main line from just outside my home due tree roots, the excavating contractor carefully dug 40' to the line that went under the garage, exposing the clay crock, he then broke them as close to garage as possible and leaving the bottons as much as possible, he then laid 3" X 10' PVC sections, glued and pushed them inside remaining clays (50') under garage just short into the main line, laid the remaining into the broken lower pieces and connected it to the C I that came out from under the basement footing using the existing slope from 1938.
He said that he disagreed in using 4" as code required plus much more excavating and a new sewer tap, since the gallons required in new toilets would not work as well (in his opinion) and could cause problems. That was 18 years ago and no problems at all not even when the city ran inspection cameras through their main line, mine was just short of being exposed in the main and not to their then code.
18 years and counting.

Sent from my SM-T387V using Tapatalk

 

[Bopbop]

Where are you located and what plumbing code are you under? The International plumbing code only requires 1/8" per foot slope for a 3 or 4" sewer line. When you increase the slope you will increase the load carrying capacity. Now does the local authority having jurisdiction require a different slope?
Yes if the slope is to great the solids and liquid can separate. However i do not think you would have an issue in the last 50 feet. You will always have more liquid than solids in the line.
I would recommend installing a cleanout at the beginning of the last 50 feet and at the exit from your building.
Most of the issues that happened with the old clay pipe or concrete systems are not an issue with the PVC drainage system

 

[abachman]

All this concern about the solids dropping out and being left behind.... remember that periodically during each day, sink water or tub/shower water will be washing down the drain, taking anything left behind.

 

[tarmy]

My run of 4” ABS is about 250’ from my shop/ bunkhouse to the tank. The drop is about 22-24’...

I have extra clean outs but have never needed them. About once a year I shove the hose in the upper clean out and run it wide open for about 5 minutes...

No plugs...

 

[johninct]

If you have to change that much height, I would not recommend a pipe going down 90 degrees but a small concrete structure where the stuff come in, drops down and then flows out. It will also serve as a cleanout .

 

[brownbagg]

run too steep and the water outruns the ****

 

[firebirdparts]

I don't think in practice this is actually a problem. It might depend on your diet. When the city put sewers in, i just did what I had to, and it's been draining for 30 years.

Let's just admit that there's no magic that's going to protect 150 feet at 1/4" a foot. That's a long way. There's a lot of paper in there. It doesn't really all keep moving.

 

[56Mark]

1/4" is minimum on a long run. With PVC you can run any pitch you want greater than that. I think the old wives tale of too much slope comes from old tile or rough concrete pipes with lots of joints and friction. More importantly is to avoid turns and 90's. If you drop vertically, use (2) 45's at the bottom instead of a 90. You want the solids to slide at the bottom of a vertical drop and not hit and splatter causing a crust to build up in that area. (2) 45's are also much easier to snake through if need be. Minimize the number of fittings and I don't think you will have any problems.