View Full Version : Long horizontal drain pipe run clogging regularly
We're having problems with our kitchen sink drain pipe. It's a double sink, and the dishwasher also hooks into the drain. After the trap and going into the wall, the 2" PVC drain pipe heads down vertically about 2 feet to our basement. At this point, it makes a right angle and heads about 16 feet horizontally, then makes another right angle and heads another 14 feet horizontally, where it finally meets a 4" vertical drain pipe. The kitchen sink and dishwasher are the only fixtures on the 30-foot run of 2" pipe. The 2" pipe has been clogging regularly since we bought the house a couple of years ago, causing water to back up in the kitchen sink, especially when the dishwasher is running.
Since it happened the first time, we've been trying to keep the pipe clear by running hot water for a few minutes every couple of weeks down the pipe, avoiding using the garbage disposal (putting solid stuff in the trash, instead), etc., but the pipe continues to clog.
My guess is that 30 feet is far too long for a horizontal run of 2" pipe, and gunk is settling in the pipe and stopping up the works. However, I don't see a straightforward way to add slope to the run. The 16-foot run does have some amount of slope to it (probably at least 1/4" per foot, but I haven't measured it), but I can't tell whether there's any slope on the 14-foot section.
Does 30 feet sound too long for a horizontal run of 2" pipe, or should it work just fine provided that a 1/4" per foot slope is maintained? Would it help to move to a larger diameter pipe? Is it possible there's just something wrong with the current pipe and replacing it with new pipe would fix the problem? Is there some kind of pump or other device I can insert to help move things along without clogging? Any other ideas?
Thanks!
jimbo
07-12-2005, 07:38 AM
Minimum slope on a 2" line is ¼" per foot, so a 30 foot run should slope 7½" from one end to the other. This is your problem.
Minimum slope on a 2" line is ¼" per foot, so a 30 foot run should slope 7½"
Okay, that's what I figured. I finally went down to the basement and actually measured the slopes. I also took a few pictures to illustrate the situation.
This is the first length of pipe, which is about 16 feet long with a slope of about 0.2"/foot (flow is towards the camera):
http://www.smugmug.com/photos/28108335-S.jpg
The pipe then drops down & turns 90 degrees via a 90-degree and 45-degree elbow (flow is to the left):
http://www.smugmug.com/photos/28108512-S.jpg
The second length of pipe is about 14 feet long with a slope of about 0.1"/foot (flow is away from the camera):
http://www.smugmug.com/photos/28108792-S.jpg
The run finally meets a 4" vertical pipe and heads down (flow is towards the camera):
http://www.smugmug.com/photos/28109075-S.jpg
The average slope over the entire 30' run is about 0.28"/foot, but of course most of that drop takes place in the 90/45 elbow construction.
The question now is, what can i do about it? To me, it looks like I need to raise the start of the 16-foot section and lower the end of the 14-foot section. I'm guessing this will require replacing and rebuilding the entire 30-foot run of 2" pipe, as well as replacing and rebuilding much of the upper 4" structure that it connects into. Is there a better or easier solution?
Thanks!
I just discovered transparent Schedule 40 PVC. As I make whatever repairs are necessary, I'm considering inserting a few short lengths of transparent pipe in strategic locations to aid in diagnosing any future clogs. Other than the higher price, are there any negatives to this approach? Is the transparent stuff fully compatible with the primers and cements used with white pipe? This would mean using a few couplings between transparent and white pipe in places that would otherwise be smooth, continuous pipe. Is that okay, or am I asking for trouble? Any good sources other than McMaster-Carr?
Thanks!
Gary Swart
07-12-2005, 02:25 PM
I am not familiar with clear PVC, but if it is true PVC, then use PVC cement and primer. I also have never heard of McMaster-Carr, but any building or plumbing supply will have PVC pipe. I don't think you need the clear stuff, but it won't hurt anything to have it and you will have peace of mind knowing you have good drainage. The real fix to your problem is to get enough slope.
jrogers99
07-15-2005, 12:17 AM
I'm new here and maybe this is way off base but I see the problem simply as a vent problem. When your run of pipe (30 feet in your case) drops more than it's diameter (2") it needs to be revented to move waste. From reviewing the pictures I'm not seeing any reventing. Could this be the problem?
"average slope" will give you misminformation. A long flat section or bellied section will lead to problems, even with an acceptable "average slope".
Paul
Most "transparent" pipe has a thicker wall than standard pipe. If that is the case with the pipe you are looking at, then your "solution" will become your problem as material gets caught against the thicker pipe and creates a clog. From your description, you may be able to revis, or create a new connection, at the terminus and then just rehang/regrade the pipe.
From your description, you may be able to revis, or create a new connection, at the terminus and then just rehang/regrade the pipe.What I have in mind is to cut off and cap the existing wye connection to the 4" pipe. Then insert a new wye to connect the regraded pipe to:
http://www.smugmug.com/photos/28463677-S.jpg
Any problems with this approach?
From reviewing the pictures I'm not seeing any reventing.That's true; there is no reventing.
When your run of pipe (30 feet in your case) drops more than it's diameter (2") it needs to be revented to move waste.Is that true regardless of how the drop occurs? In my case, almost all of the drop happens suddenly at the 90-degree turn:
http://www.smugmug.com/photos/28108512-S.jpg
I can also envision a long, constant-slop pipe eventually dropping more than its diameter, but in my case, the two constant-slope sections have very little slope.
If I need to add a vent, where (and how) should I add it? The situation is complicated by the fact that the space above is completely open (vaulted/cathedral ceiling); there are no walls leading to the attic space until the pipe reaches the far side of the stairway near the 4" vertical. You can see the furnace vent heading up this wall in first photo of this post.
"average slope" will give you misminformation. A long flat section or bellied section will lead to problems, even with an acceptable "average slope".Yep, I should'nt have mentioned it ... I calculated the "average" slope out of curiosity, but it's not relevant and may be confusing the issue. Please ignore. :)
casman
07-15-2005, 10:26 AM
Although I'm not a pumber your proposed drawing/pic is the same setup I am running and I've never had problems with it clogging. Hopefully it's ok cause I've never heard of doing a revent thing cause of the 2 inch diameter drop post and if true then mines wrong as well....
You do not have to "revent" the pipe.The only vent you need should be in the wall where the sink drain connects to the vertical pipe.
plumguy
07-16-2005, 03:22 AM
It definately looks like you can fix that run by lowering the wye like you show in the pic. Just remember that 1/4" per foot is not the minimum, it is the pitch you want. Too much pitch can be just as bad as not enough.
SteveW
07-16-2005, 04:43 AM
It definately looks like you can fix that run by lowering the wye like you show in the pic. Just remember that 1/4" per foot is not the minimum, it is the pitch you want. Too much pitch can be just as bad as not enough.
How can too much pitch be harmful?
plumguy
07-16-2005, 05:04 AM
How can too much pitch be harmful?
Let's use a toilet drain as an example. On a horizontal run pitch greater than 1/4" the solids could be left behind and the water will flow without carrying them downstream and obviously solids left will eventually contribute to a blockage. In theory and engineering design 1/4" per foot is the correct pitch for water and solids to evenly flow downstream.
I can barely make out that the 90 turning up to go to the kitchen sink looks as if the "cup" is tight to the underside of the floor.That sets the start of the first long run.So getting slope from that 90 across the ceiling and still staying on top of the duct is most likely too flat. (Sorry,all of the above is obvious just recapping)Can you cut the line under the kitchen sink and open the hole around the 90 under the floor, thus raising the starting center point ? Is it a traditional vent,island vent or in-line vent ? I KNOW this is stupid,,,,Has it been snaked ? By the way ,,,the 3 x 2 wye on the vertical stack is a GOOD idea.
plumguy
07-16-2005, 05:33 AM
I can barely make out that the 90 turning up to go to the kitchen sink looks as if the "cup" is tight to the underside of the floor.That sets the start of the first long run.So getting slope from that 90 across the ceiling and still staying on top of the duct is most likely too flat. (Sorry,all of the above is obvious just recapping)Can you cut the line under the kitchen sink and open the hole around the 90 under the floor, thus raising the starting center point ? Is it a traditional vent,island vent or in-line vent ? I KNOW this is stupid,,,,Has it been snaked ? By the way ,,,the 3 x 2 wye on the vertical stack is a GOOD idea.
I can't see the 90 either and would hope it is a long sweep. But, I think "recapping" gives him a majority vote on minimal work to help with the problem. "Has it been snaked" If it continuosly clogs I would imagine it has.I'm sorry,but I don't think it is an island sink ( and how would that matter?) it looks like it "turns up" above a foundation on a outside wall, plus, I think you would see the bow (loop) vent next to the drain! . And I'm just curious what is the difference between a "traditonal vent" and "in-line vent".
Plum,
I just meant can he see the venting under the sink or is it a vent that runs up inside the wall. I am very fond of these new in-line ( Studor model) vents.
It would be nice if he could just re-run the entire line and be done with it.
plumguy
07-16-2005, 06:05 AM
Hey Cal, I hear you. I thought that might be what you meant, but I guess it depends where you are from! Those mechanical vents are illegal here in MA and are not an option. So, sometimes it makes you approach a job or problem differently. I myself would rip it out and replace it, considering the cost of pvc and being a short run.But, it comes down too one's budget and ability!
But, that it is why a forum like this can be so valuable and interesting!
toolaholic
07-16-2005, 09:00 PM
who signed that job off? :confused:
toolaholic
07-16-2005, 09:07 PM
only with inspectors permission and have to be accessable not buried
Thanks, guys, for all your help and advice! Here's an update.
My wife and I completed Phase 1 of this project on Saturday: buying all the fittings we might need and tearing out the old pipe. What a stinky, messy, disgusting mess that was! Good thing we have an unfinished basement!
Here's some sections of the second (14-foot) length of pipe after they were cut out:
http://www.smugmug.com/photos/28666899-S.jpg
Yuck!
The entire length of this section was pretty much the same; the first (16-foot) section was much cleaner. Both were pretty much what I expected, except I expected the gunk to be a soft sludge; instead, much of it was rock hard.
Has it been snaked?Not professionally since we bought the house two years ago, but I did attack it with a hand snake last year. It helped, but when it clogged again this week, I resolved to actually fix the problem rather than just snaking it again.
After removing the pipe, I studied more closely the point where the pipe enters the basement from the sink:
http://www.smugmug.com/photos/28666905-S.jpg
My original plan was to cut this off right above the 90-degree bend and install a new 90-degree bend about an inch or so higher, thus increasing the slope towards the ductwork. That's still what I'd like to do, but notice how the pipe comes out right against the 2x10. The original installer had to burrow out part of the 2x10 to provide enough room for the flange of the elbow. If I remove this elbow, I'll be facing the same problem. How do I burrow out the 2x10 around the pipe without damaging the pipe in the process? Note that this pipe heads up into an exterior wall behind the kitchen cabinets, so there's no access from above.
Alternatively, I could leave the existing elbow alone and run new pipe from the exit of the elbow. This would give me only 0.2"/foot of slope, but it's seemed to work okay thus far: all of the blockage was in the second section that sloped at only 0.1"/foot. This section had a thin layer of soft sludge, but was generally clear.
Thoughts? Install a new elbow an inch or so higher (how to deal with the 2x10?) or leave it alone and live with only 0.2"/foot of slope for 16 feet?
Next topic: the new wye at the end of the run. I could go with a long bend:
http://www.smugmug.com/photos/28666906-S.jpg
Or I could go with a 45-degree wye:
http://www.smugmug.com/photos/28666907-S.jpg
I can mount the long bend higher on the 3" vertical, minimizing the intrusion into the living space. On the other hand, the 45-degree wye provides a steep slope at the end. I'd rather go with the long bend unless it could cause a problem.
(Ignore the location of the cap on the 2" pipe in these photos. It's not welded on yet; I just stuck it on dry to block any sewer fumes. I'm going to cut off that remaining length of pipe and cap right by the wye.)
1/4" per foot is not the minimum, it is the pitch you want. Too much pitch can be just as bad as not enough. ... In theory and engineering design 1/4" per foot is the correct pitch for water and solids to evenly flow downstream.So it seems that too little slope is bad, then around 0.25"/foot is good, and more than that is bad ... except that at some point as the slope becomes more and more vertical (maybe around 45 degrees?), it obviously becomes good again. Interesting. I would like to learn more about this. (I can't help myself; I'm an engineer, and I always have to know how and why things work.) Can you direct me to a book or website that discusses this in more detail?
Going back to the "too much pitch" statement. EXTENSIVE testing has proven that there is no truth to the "solids get left behind" theory. If that were the case pipes with the maximum pitch, namely vertical, and 45 degree slopes would be illegal.
toolaholic
07-17-2005, 07:07 AM
Do You Have Some Documantion On This You Can Share ?
I,d Appreciate It Thanks
toolaholic
07-17-2005, 07:12 AM
this is the best post .why not bring it to the attention of the building dept.
there is a name of the inspector that signed it off. i.ll bet a $100 he never worked in the trade,and was a political appt.
also the plumb. cont. should get these pix and pay you well for your time!
this work is outragous!
master plumber mark
07-17-2005, 08:26 AM
what you posted will work real good....
you might even want take that 3 inch wye down as
low as possible.... a lot lower
what MR HI said is right,
you can give it all the fall you want
nothing is gonna get left behind......
make the 2 inch take a steep dive down to the 3 inch wye.
just take that 2 inch back as far as you can and
give it all a good amount of fall....
it will work fine
just ease up on the bacon grease
Dunbar Plumbing
07-17-2005, 10:41 AM
Hydraulic Jump is common where the solids build up a few feet beyond the base of a vertical stack if a 90 is used at the base. Code requires a turn of direction of double 45's to control this problem. This usually is required on buildings more than 3 stories high/40 linear feet of vertical stack.
plumguy
07-17-2005, 10:45 AM
Going back to the "too much pitch" statement. EXTENSIVE testing has proven that there is no truth to the "solids get left behind" theory. If that were the case pipes with the maximum pitch, namely vertical, and 45 degree slopes would be illegal.
Comparing horizontal piping and vertical piping is like apples and oranges. However, I'd like to read that info, because personally I don't care for engineers and since they designed the plumbing system that we all know and love I'd like too prove them wrong!!
Hydraulic Jump is common where the solids build up a few feet beyond the base of a vertical stack if a 90 is used at the baseI did a Google search, and it looks like this occurs when a long vertical feeds into a horizontal. Is that right? Not sure how this is relevant in my situation ...
just ease up on the bacon greaseI suspect most of that was donated by the previous owners. :) The house is 14 years old, and we've only lived here the last two.
personally I don't care for engineersUh oh ... Did I mention I'm an engineer? I meant racketeer! Yeah, that's it, I'm a racketeer! ... (Wait, is that worse?) :)
Any insight into how to burrow out the 2x10 for a flange?
http://www.smugmug.com/photos/28666905-S.jpg
Dremel tool? Grinder? Recipricating saw? Avoid the problem and just live with 0.2"/foot slope for the first 16 feet?
Thanks!
Dunbar Plumbing
07-17-2005, 12:16 PM
That was mentioned to the the plumbers on this thread, not you.
plumguy
07-17-2005, 05:19 PM
Hydraulic Jump is common where the solids build up a few feet beyond the base of a vertical stack if a 90 is used at the base. Code requires a turn of direction of double 45's to control this problem. This usually is required on buildings more than 3 stories high/40 linear feet of vertical stack.
Code is the same here. Horizontal to vertical you can use regular 90. Vertical to horizontal you must use long sweep. That's why I'd like too see more info about excessive pitch not being an issue as stated above.
If it is true that would mean that engineers have lied to us all these years!!? :confused: And just when you thought it could'nt get any worse...OH wait a minute lawyers wrote the codes! :confused:
plumguy
07-17-2005, 06:11 PM
Thanks, guys, for all your help and advice! Here's an update.
My wife and I completed Phase 1 of this project on Saturday: buying all the fittings we might need and tearing out the old pipe. What a stinky, messy, disgusting mess that was! Good thing we have an unfinished basement!
Here's some sections of the second (14-foot) length of pipe after they were cut out:
http://www.smugmug.com/photos/28666899-S.jpg
Yuck!
The entire length of this section was pretty much the same; the first (16-foot) section was much cleaner. Both were pretty much what I expected, except I expected the gunk to be a soft sludge; instead, much of it was rock hard.
Not professionally since we bought the house two years ago, but I did attack it with a hand snake last year. It helped, but when it clogged again this week, I resolved to actually fix the problem rather than just snaking it again.
After removing the pipe, I studied more closely the point where the pipe enters the basement from the sink:
http://www.smugmug.com/photos/28666905-S.jpg
My original plan was to cut this off right above the 90-degree bend and install a new 90-degree bend about an inch or so higher, thus increasing the slope towards the ductwork. That's still what I'd like to do, but notice how the pipe comes out right against the 2x10. The original installer had to burrow out part of the 2x10 to provide enough room for the flange of the elbow. If I remove this elbow, I'll be facing the same problem. How do I burrow out the 2x10 around the pipe without damaging the pipe in the process? Note that this pipe heads up into an exterior wall behind the kitchen cabinets, so there's no access from above.
Alternatively, I could leave the existing elbow alone and run new pipe from the exit of the elbow. This would give me only 0.2"/foot of slope, but it's seemed to work okay thus far: all of the blockage was in the second section that sloped at only 0.1"/foot. This section had a thin layer of soft sludge, but was generally clear.
Thoughts? Install a new elbow an inch or so higher (how to deal with the 2x10?) or leave it alone and live with only 0.2"/foot of slope for 16 feet?
Next topic: the new wye at the end of the run. I could go with a long bend:
http://www.smugmug.com/photos/28666906-S.jpg
Or I could go with a 45-degree wye:
http://www.smugmug.com/photos/28666907-S.jpg
I can mount the long bend higher on the 3" vertical, minimizing the intrusion into the living space. On the other hand, the 45-degree wye provides a steep slope at the end. I'd rather go with the long bend unless it could cause a problem.
(Ignore the location of the cap on the 2" pipe in these photos. It's not welded on yet; I just stuck it on dry to block any sewer fumes. I'm going to cut off that remaining length of pipe and cap right by the wye.)
So it seems that too little slope is bad, then around 0.25"/foot is good, and more than that is bad ... except that at some point as the slope becomes more and more vertical (maybe around 45 degrees?), it obviously becomes good again. Interesting. I would like to learn more about this. (I can't help myself; I'm an engineer, and I always have to know how and why things work.) Can you direct me to a book or website that discusses this in more detail?
Here is some reading for you, http://www.mass.gov/dpl/boards/pl/cmr.htm. You can email the board and their engineers with any questions! Please educate us when you get back. Thanks
Oh by the way, I think you should be ashamed of yourself for coming out here for free advice. You know you are going to google everything we tell you and question everything we have to say. I could tell you were an engineer(typical) from the beginning. Be honest you are going to do it you're way. Let someone who needs help benefit from this forum.
Oh by the way, I think you should be ashamed of yourself for coming out here for free advice. You know you are going to google everything we tell you and question everything we have to say. I could tell you were an engineer(typical) from the beginning. Be honest you are going to do it you're way. Let someone who needs help benefit from this forum.Huh? :confused: I'm not sure what I wrote that touched a nerve, but it whatever it was must have lost its intended meaning or tone. If this in response for my seeking more detail about slope (too much, too little, etc.), I wasn't questioning the validity of your statement; I was honestly interested and curious to learn more. Some people like playing basketball; I like learning about stuff. Probably why I became an engineer. If this is about the engineer/racketeer comment, I was just trying to make a light-hearted joke. Sorry if it didn't come across that way. Whenever I try to try to write something funny in an email or on-line, it often backfires and doesn't come across the way I intended. I probably should stop trying.
I came to this forum as a homeowner seeking advice and wisdom from those more knowledgeable and experienced in plumbing than I am. I may be an engineer, but I'm the type that deals with electricity. I have very little plumbing experience (and until this weekend, absolutely none with running DWV pipe). Whenever I need to do something I don't know how to do or have never done before, I want to learn all I can before I dive in, lest I make some newbie mistake that I later regret. Yes, I've Googled a couple of things mentioned here when I didn't understand what the poster was talking about, but I'm not going around double-checking everything everybody says. On the contrary, I trust the knowledge and experience of the plumbers on this site far more than something "out there" on the Internet. Google searches tend to turn up a lot of conflicting information, some written by people who know what they're talking about, but a lot written by people who don't, and it's hard to tell which is which. I'd much rather come someplace like this, where all the experts hang out, for the real story.
Thanks to everyone for your help and advice. If I offended anyone else, I'm sorry; I didn't mean to.
plumguy
07-17-2005, 08:19 PM
Huh? :confused: I'm not sure what I wrote that touched a nerve, but it whatever it was must have lost its intended meaning or tone. If this in response for my seeking more detail about slope (too much, too little, etc.), I wasn't questioning the validity of your statement; I was honestly interested and curious to learn more. Some people like playing basketball; I like learning about stuff. Probably why I became an engineer. If this is about the engineer/racketeer comment, I was just trying to make a light-hearted joke. Sorry if it didn't come across that way. Whenever I try to try to write something funny in an email or on-line, it often backfires and doesn't come across the way I intended. I probably should stop trying.
I came to this forum as a homeowner seeking advice and wisdom from those more knowledgeable and experienced in plumbing than I am. I may be an engineer, but I'm the type that deals with electricity. I have very little plumbing experience (and until this weekend, absolutely none with running DWV pipe). Whenever I need to do something I don't know how to do or have never done before, I want to learn all I can before I dive in, lest I make some newbie mistake that I later regret. Yes, I've Googled a couple of things mentioned here when I didn't understand what the poster was talking about, but I'm not going around double-checking everything everybody says. On the contrary, I trust the knowledge and experience of the plumbers on this site far more than something "out there" on the Internet. Google searches tend to turn up a lot of conflicting information, some written by people who know what they're talking about, but a lot written by people who don't, and it's hard to tell which is which. I'd much rather come someplace like this, where all the experts hang out, for the real story.
Thanks to everyone for your help and advice. If I offended anyone else, I'm sorry; I didn't mean to.
I have also in the past been accused of emails,etc of being harsh or taken the wrong way. I'am also a newbie out here but certainly not in the trade.
Of course my posts are just my opinion and that is what is so valuable about this type of forum, getting different perspectives from pro's around the country!
I was serious about the website I provided you with, I would like feedback from you after you're research. Our code was just rewritten because most codes could be interpreted differently and would cause conflict between inspectors and plumbers! So, you get to look at the new version and click into sanitary drainage systems.
Oh by the way you did'nt hit a "nerve" and there was no need for an apology!! I would of never responded again to you're posts or had the decency to leave you that website if a "nerve" was struck. And you're thankfulness to those who contributed to helping you in you're project was very nice. See, my outlook of engineers is already starting to change! :D Thanks
plumber1
08-14-2005, 05:37 PM
That sort of layout just begs to be plugged. Has the drain ever been cleaned out before? As long as there is pitch it's ok.
I would put an 11/2' plug somewhere under the sink upstream of the last trap
and use it for a clean out. Rent or borrow a RIDIGED small drain cleaner and clean the drain the proper way. You might to put a small kink in the lead section of snake to make it flop around. Once you get the snake all the way into the 3''or 4" pipe, start to run water and back out the snake. The drain will be cleaned well and the snake will come back clean and not make much of a mess in the kitchen.
Oops, I got in too late!!!