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Topic:   Drain pipe slope - 11463 visits (5 today, 52 this week)

Steven Brewster
New Member


Posts: 6
From:Southside, AL
Registered: Oct 2005

posted October 18, 2005 04:58 PM         

Hey Folks,

Anyone got a code ref. for the max. allowable slope of a drain pipe? Iv'e run across several of these lately.

Click for photo (175487 Bytes)
Click for photo (185497 Bytes)

Just seems like the liquid will outrun the solid.

Gunnar Alquist
Member


Posts: 984
From:Santa Rosa, CA
Registered: Jan 2001

posted October 18, 2005 10:17 PM            

Steven,

Well, since the soil pipe can run straight down the interior of a wall, it seems to me that any angle between 1/4" per foot and vertical is OK. I have never heard anyone say that the drop was too steep.

Brian Goodman
Member


Posts: 415
From:Columbus, MS
Registered: Jan 2005

posted October 19, 2005 09:19 AM         

I've heard plumbers say the slope can be too steep and the water will run off and leave the solids behind, but I have no personal experience in that area. When it's falling straight down it all moves at pretty much the same speed, and the solids aren't likely to stop there.

A quick look in the IRC shows only a minimum though (P3005.3 says "not less than one-fourth unit vertical in 12 units horizontal"), no maximum slope listed.

[This message has been edited by Brian Goodman (edited October 19, 2005).]

Eric Laney
Member


Posts: 79
From:Georgetown, TX
Registered: May 2005

posted October 19, 2005 02:23 PM            

I don't have a code ref, but my plumbing book from HI school says any slope over 1/2" will leave the poop in the schute

Rick Hurst
Member



Posts: 3694
From:Rockwall, TX
Registered: Oct 2003

posted October 19, 2005 03:48 PM            

Take a laxative then.

I was at a home the other day that had the drain line to the septic all backed up. The plumber said he was going to dig up the line.

I told him the house was occupied by a few ladies and bet it was what we call "Bunny tails". Sure enough that was the blockage. Cleared them out, and end of the problem.

Rick

[This message has been edited by Rick Hurst (edited October 19, 2005).]

Jerry Peck
Member




Posts: 7637
From:Pembroke Pines, FL
Registered: Feb 2003

posted October 19, 2005 04:28 PM            

From the 2003 IRC.
- P3005.4.2 Building drain and sewer size and slope. Pipe sizes and slope shall be determined from Table P3005.4.2 on the basis of drainage load in fixture units (d.f.u.) computed from Table P3004.1.
(then there is Table P3005.4.2)

Table 3005.4.2 basically says: The slope for a given size affects the number of fixture units allowed on that drain, i.e.,
- 1-1/2" can either be 1/4" per foot or 1/2" per foot
- 2" can be either 1/4" per foot or 1/2" per foot
- 2-1/2" can be either 1/4" per foot or 1/2" per foot
- 3" can be 1/8" per foot, 1/4" per foot or 1/2" per foot
- 4" can be 1/8" per foot, 1/4" per foot or 1/2" per foot
then the table gives the maximum number of fixture units per size based on slope

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Jerry Peck
South Florida

Brian Goodman
Member


Posts: 415
From:Columbus, MS
Registered: Jan 2005

posted October 19, 2005 05:21 PM         

From the 2003 IRC.
- P3005.4.2 Building drain and sewer size and slope.

Doesn't that refer only to the main line going out?

Jerry Peck
Member




Posts: 7637
From:Pembroke Pines, FL
Registered: Feb 2003

posted October 19, 2005 05:34 PM            

"
- P3005.4.2 Building drain and sewer size and slope.
Doesn't that refer only to the main line going out?
"

No. See bold above.

1-1/2" size has two notes, a and b.

a. 1-1/2" pipe size limited to building drain branch serving not more than two waste fixtures, or not more than one waste fixture if serving a pumped discharge fixture or garbage grinder discharge
b. no water closets

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Jerry Peck
South Florida

Michael Thomas
Member


Posts: 149
From:Evanston, IL
Registered: Jul 2005

posted October 19, 2005 06:48 PM            

I was told a while back by an (Evanston IL) residential plumbing inspector it's the min & max from Jerry's table above OR 45 degrees or greater. He will likely be the inspector for the final on one of my projects in a few weeks, and I'll ask him again and see if he can provide a cite.

[This message has been edited by Michael Thomas (edited October 19, 2005).]

Brian Goodman
Member


Posts: 415
From:Columbus, MS
Registered: Jan 2005

posted October 19, 2005 09:47 PM         

No. See bold above.

1-1/2" size has two notes, a and b.

a. 1-1/2" pipe size limited to building drain branch serving not more than two waste fixtures, or not more than one waste fixture if serving a pumped discharge fixture or garbage grinder discharge
b. no water closets

Ah-so. Got it. Anyone know where they came up with the term "water closets"?

Joe Nernberg
Member


Posts: 669
From:Agoura Hills, CA
Registered: Jan 2001

posted October 19, 2005 10:19 PM            

Steven,

I don't believe this drain construction should concern you. A "Y" or "Combo" fitting should be rolled up at a 45-degree angle as shown. Consider a drain/sewer that must run down a hillside: straight shot at a 45-degee angle or several switch-backs? Drain stoppages occur at changes in direction. It's the low-flow toilets that are responsible for slow drainage.

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Joe Nernberg

Richard Moore
Member



Posts: 1155
From:Seattle, WA
Registered: Feb 2003

posted October 19, 2005 11:57 PM            

I just can't buy the theory that any slope over 1/2" per foot wiil leave the solids behind. Faster flowing water would tend to carry the solids better rather than dropping them.

Table 3005.4.2 gives the maximum number of fixture units for a given slope. It does not state those slopes as maximums.

Briefly, P3005.3 states that horizontal piping shall be installed at not less than 1/4" (or 1/8") per foot. The UPC says the same. They do say that the slope should be uniform, but I'm guessing that "maximum slope" isn't mentioned anywhere for good reason (for branch or sewer drains).

Hell, I'd have to call almost every home with a crawl for "excessive slope" if 1/2" per foot was the maximum.

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Richard Moore
Rest Assured Inspection Services
Seattle
www.rainspect.com

[This message has been edited by Richard Moore (edited October 19, 2005).]

Jerry Peck
Member




Posts: 7637
From:Pembroke Pines, FL
Registered: Feb 2003

posted October 20, 2005 05:22 AM            

"Anyone know where they came up with the term "water closets"?"

The toilet was invented by Thomas P Crapper, and, since there were no "bathrooms" at that time, The Crapper was installed in a closet.

If you had a Crapper, you had a 'water closet'.

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Jerry Peck
South Florida

Michael Thomas
Member


Posts: 149
From:Evanston, IL
Registered: Jul 2005

posted October 20, 2005 07:56 AM            

Richard,

FWIW, here's the theory behind the min-max pitch:

Click for photo (55996 Bytes)

I’ve read several times that this was originally set as a result of practical experience and later confirmed by actual experiment - in any case I do know from personal experience that at least in my AHJ inspectors will demand correction of work obviously exceeding ˝” per foot in “horizontal” pipe runs unless the slope is also (as I remember it) 45 degrees or greater.

Rick Hurst
Member



Posts: 3694
From:Rockwall, TX
Registered: Oct 2003

posted October 20, 2005 08:19 AM            

Good picture there.

You have to admit its funny though. What are those solids supposed to be?

Rick

Phillip Smith
Member


Posts: 415
From:Samantha, Alabama
Registered: Feb 2003

posted October 20, 2005 10:36 AM            

Baby Ruth's (Caddy Shack)

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Have a good day inspecting.
Phillip Smith
Samantha, (Tuscaloosa) Al.
http://www.homesweethomeinspectionsal.com/

Richard Moore
Member



Posts: 1155
From:Seattle, WA
Registered: Feb 2003

posted October 20, 2005 12:15 PM            

Michael...

Yep, good diagram, but my "logic center" is still not processing it. Where is it from? I can't stop wondering why faster running mountain streams aren't then full of bear poop and silt? I certainly cannot say anyone is wrong but it doesn't compute in my head. Both waste drainage and gravity have been around long enough that I would expect to see some definitive code if this was a known problem.

In fairness, there is this...

Click for photo (107765 Bytes)

...but note that it's for combo drain/vent lines only and specifically omits WC's and disposals, the two most likely source of "solids".

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Richard Moore
Rest Assured Inspection Services
Seattle
www.rainspect.com

Jerry Peck
Member




Posts: 7637
From:Pembroke Pines, FL
Registered: Feb 2003

posted October 20, 2005 12:56 PM            

Richard,

"I can't stop wondering why faster running mountain streams aren't then full of bear poop and silt?"

Have your "logic center" process the fact that waste flushed down a toilet or sink has a limited amount of water with it.

Your mountain stream has a never ending flow of water, pushing and pushing and pushing the waste down the stream. If the solids get left behind, there is more water right behind it to push the solids a little farther, etc., until the stream freezes over.

However, to show you that it does work that EVEN IN a full flowing mountain stream, think about ...

... panning for gold and how come the gold was even still there and not flushed down the stream?

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Jerry Peck
South Florida

Michael Thomas
Member


Posts: 149
From:Evanston, IL
Registered: Jul 2005

posted October 20, 2005 03:05 PM            

> Where is it from?

That's one Carson Dunlop uses in their books, I've seem a number of similar illustrations, including one where they flushed “solids” down clear plastic pipes at varying angles to provide a “graphic” illustrations of the principle - if inquiring minds *really* want to know, here's a source for clear schedule 40 pipe:

http://www.harvel.com/news-2005-03-18.asp

those with a skeptical and scientific turn of mind could plumb a DWV system the stuff, gradually jack one side of the house 64ths at a time, and observe the results.

Myself, I'm content to read the book.

[This message has been edited by Michael Thomas (edited October 20, 2005).]

Richard Moore
Member



Posts: 1155
From:Seattle, WA
Registered: Feb 2003

posted October 20, 2005 03:11 PM            

LOL...if I pooped gold nuggets I wouldn't be a home inspector. But we're taling about solids that have almost neutral bouyancy in water, not one of the most dense elements or even rocks. I'm also personally not one of the denser elements, and I did take into account the limited or sporadic amount of water. I still don't see that semi-floating solids would tend to be "left behind" in a faster, more forceful flow.

Seattle is a very hilly area and I guarantee that many sewer lines from the homes are way more than 4% grade. I guess I'll restate...If more than 4% or 1/2" in 12" slope is a well known and documented problem, then why would maximum slopes for regular waste/sewer lines not be in the codes?

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Richard Moore
Rest Assured Inspection Services
Seattle
www.rainspect.com

Richard Moore
Member



Posts: 1155
From:Seattle, WA
Registered: Feb 2003

posted October 20, 2005 03:17 PM            

Thanks Michael.

I'm still not convinced but I'm going out right now to get some large pneumatic jacks.

RM

Jerry Peck
Member




Posts: 7637
From:Pembroke Pines, FL
Registered: Feb 2003

posted October 20, 2005 04:46 PM            

"But we're taling about solids that have almost neutral bouyancy in water,"

No ... those are called "floaters".

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Jerry Peck
South Florida

Brian Goodman
Member


Posts: 415
From:Columbus, MS
Registered: Jan 2005

posted October 20, 2005 08:05 PM         

The toilet was invented by Thomas P Crapper, and, since there were no "bathrooms" at that time, The Crapper was installed in a closet.

The History Channel says that's a myth. I can't recall offhand who they gave credit to, but he was well before Crapper. Crapper's name survived because he was very successful and installed tons of 'em.

Jerry Peck
Member




Posts: 7637
From:Pembroke Pines, FL
Registered: Feb 2003

posted October 21, 2005 05:22 AM            

quote:

---

The toilet was invented by Thomas P Crapper, ...

The History Channel says that's a myth.

---

I will be more specific for you.

The MODERN FLUSH toilet was invented by Thomas P Crapper, ...

Toilets, receptacles where you deposited your waste, have been around a long, long time, that is probably what the History Channel is referring to.

MODERN FLUSH toilets are a fairly recent invention, by Thomas P Crapper.

There may have been other people who "invented it" too. Back when it was "invented" it was not uncommon for different people around the world to come up with similar things - word did not travel very fast back then, but needs were the same all over, and ingenuity is everywhere - sometimes resulting in similar things being "invented" for a "need" in more than one place at the same time.

Yes, the one who was "first" and patents and sells their invention is the one who is given credit.

Christopher Columbus "discovered" America, except that there were already people living here when he "discovered" it. So I think it can be said that someone beat him to it.

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Jerry Peck
South Florida

Richard Stanley
Member


Posts: 753
From:Corpus Christi, TX
Registered: Sep 2002

posted October 21, 2005 05:38 AM            

If the slope is too steep, it doesn't allow the "scouring" action of the water flow which is what moves the solid waste more efficiently.
(edit - spelling and ps)
PS. Where is thread drift when we need it?

[This message has been edited by Richard Stanley (edited October 21, 2005).]

Joshua Hardesty
New Member


Posts: 14
From:Raleigh, NC
Registered: Aug 2005

posted October 21, 2005 09:52 PM         

I've had some inspectors complain about the slopes being too great because of the water outrunning the solids, but then you'll see all kinds of connections to city sewer pipes running at relatively steep angles.

Rick Hurst
Member



Posts: 3694
From:Rockwall, TX
Registered: Oct 2003

posted October 21, 2005 10:33 PM            

Richard,

You want some thread drift, here you go.
Click for photo (77345 Bytes)

Rick

Jerry Peck
Member




Posts: 7637
From:Pembroke Pines, FL
Registered: Feb 2003

posted October 22, 2005 05:56 AM            

45 degrees and over is considered 'vertical', which is okay.

Less than 45 degrees is considered 'horizontal' and must meet the proper slope.

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Jerry Peck
South Florida

Tony Keith
Member


Posts: 199
From:Aurora, IL
Registered: Aug 2005

posted October 22, 2005 06:09 AM            

The toilet was invented by Thomas P Crapper, and, since there were no "bathrooms" at that time, The Crapper was installed in a closet.

If you could only enter this closet through a bedroom, does the lighting have to be AFCI protected. ?

Richard Stanley
Member


Posts: 753
From:Corpus Christi, TX
Registered: Sep 2002

posted October 22, 2005 06:11 AM            

Rick, Cute. Homeland security advises that you not post family pictures!!!

Rick Hurst
Member



Posts: 3694
From:Rockwall, TX
Registered: Oct 2003

posted October 22, 2005 07:58 AM            

One of America new super heroes there. She must be from Texas with that big hair.

Rick

Brian Goodman
Member


Posts: 415
From:Columbus, MS
Registered: Jan 2005

posted October 22, 2005 11:45 PM         

I will be more specific for you.

The MODERN FLUSH toilet was invented by Thomas P Crapper, ...

Check this link.
http://www.snopes.com/business/names/crapper.asp

Jerry Peck
Member




Posts: 7637
From:Pembroke Pines, FL
Registered: Feb 2003

posted October 23, 2005 07:45 AM            

Okay ... I will go to my corner and be quiet for 2 hours ...

.

.

.

.

Has it been 2 hours yet?

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Jerry Peck
South Florida

Andrew Buckwell
Member


Posts: 51
From:Sierra Madre, California
Registered: Feb 2002

posted December 05, 2005 07:10 PM            

The Water Closet actually appears to date back to the 16th century. http://www.theplumber.com/closet.html