Shower rough in has standing sewage?

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Bacon

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In the process of finishing off a basement bath that had rough ins installed when we built the house 3 years ago. I was about to install the shower p-trap but when I cut the cap off the 2" stub below the concrete slab, there was some standing sludge/sewage in the pipe. There was no liquid, but it was soft and stinky and about 3/4"deep in a 2" pipe. It had little bugs crawling in it too. Is this normal for something that has been capped off, or is this backflow from the main stack about 5ft away? There shouldn't be anything else draining in this pipe, and I would think the connection at the main stack would prevent any backflow.

Thanks for your thoughts
 

Bacon

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Here are pictures of the layout and the cap that I cut off. The rough-in was done assuming a tub would be installed, but I opted for shower only. As a result, I cut the floor out so that I could have a central drain and symmetrical shower pan. The rough-in stub on the right is 2" PVC and it turns 90deg to the right and I assume goes straight over to the main 4" stack for the house. About 12" from the cap there is a vertical vent line. As far as I can tell, there shouldnt be anything else connected to this piping.

20170225_164550.jpg
20170225_205619.jpg
 

Terry

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Without seeing what is behind wall number 2, it's only a guess.
I would say that normally with proper grading, and proper fittings, that it should have been clean. I did run into one home that used a santee at the base of a stack, and the waste dropping down and hitting the tee caused the solids to go both directions.
That's why I use a wye fitting or long sweep 90 at the base. A wye fitting at the base would be wye with 45, or a combo fitting. Basicly like a tee, but with a long sweep that moves the solids and water down the line.

abs_wye_combo.jpg


The combo and the wye can be used at the base of a stack or also on the horizontal.

abs_tee.jpg

A santee. I only use these on the vertical.
 

Bacon

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So what happens if they used a santee on the horizontal under the slab? I came almost every day during the build to take pictures, but they managed to lay plumbing, rock, radon barrier, and slab all in one day, so I never saw it. I have the installer coming Monday to look at a very crooked water closet rough in about 3ft away - should I grille them on this too?

Was really hoping to get some stuff done this weekend...
 

Cacher_Chick

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It is not right, but with water flowing down the pipe after the shower is connected, it may not cause a problem. Given that you are already busting concrete, you have to weigh the cost of looking into it now vs. the possibility that it might need to be corrected later.
 

Dj2

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You have the plumber coming over, by all means, call his attention to this deficiency and take care of it now, not later.
 

Bacon

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I believe my setup is constructed very similar to this aside from the fact that my sink stub and trap go directly to the stack about 24" away and do not have a separate vent line.

While running the shower would hopefully clear some waste in the future, it is a basement bath that will be used infrequently. I fear it would build up quicker than it would clear out. If the pipe had the proper slope to it, wouldnt any falling liquid/solids entering from the main stack just drain back out? How did it get all they way to my shower stub unless it's sloped backwards? Is this something the inspector should have caught? Or is it more likely that it moved out of place when the rock under the slab was put in place?

bathroom%20drain%20plumbing%20cr.jpg
 

Cacher_Chick

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If that were your layout, where would the sewage be coming from given the WC connection is lower on the stack.

One possibility is that the system had a backup which receeded before it made its way up to where you would have noticed it. The liquid flowed back down, but some of the solids were left behind.
 

Bacon

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I guess it's similar, but not the same. I have a main stack that services the main and second floor. Falling waste from those toilets could have caught the T as Terry suggested and flowed the wrong way if incorrectly sloped.
 

Cacher_Chick

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It would be more common for the basement fixtures to be tied into the horizontal building drain. It could be set up that way, but in most installs I have seen the stack is turning horizontal right below the floor.

There should be a cleanout at the base of the stack, above the floor. Maybe you can snap some pics down through that or use a light and mirror to see what happens on the vertical below the floor.
 

Kreemoweet

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bacon said:
Is this something the inspector should have caught?
.

In light of your story that the pipes were laid, and slab poured all on the same day, it doesn't seem very likely that it was ever
inspected.

If there's no backup currently into the shwr drain pipe when upper toilets are flushed, why would there be in the
future? The shwr drain can be tested by running water into it: if it does not backflow, and drains completely,
then there's no reverse slope.
 

Bacon

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Plumber was out yesterday and it was about what I expected. I know the guy and like him, but he didnt seem concerned at all. He said I could have the line scoped and if there was a plumbing issue they would pay for it. Before I dropped $200 on a scope job, I decided to do some more investigation myself.

I basically built up my P-trap and arm assembly, but instead of gluing the final coupling in place at the stub, i connected it with a Fernco fitting. I flushed it with about 10gal of hot water and some Trift cleaner and planned on snaking it afterwards with a constant flow of water, but the pipe was perfectly clean when I took my assembly off. I put a hose about 2ft in and turned it on slowly and everything drains away indicating proper slope.

No idea where all that stuff came from, but it's gone now and I didnt even have to clean a dirty snake afterwards. The plumber seems to think it could have been something from the construction crew during the build. He said they see all kinds of crazy stuff like concrete down the floor drain, people taking a #2 in floor drains/pipes, etc.

Thanks for all the thoughts along the way - just wanted to bring closure to this one. Concrete is going back in tonight and that feels good!
 

Bacon

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Forgot to mention, I also flushed all the toilets and ran all the fixtures (tubs, showers, sinks) with cap off of that pipe and never saw anything come out.
 

Bacon

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I buttoned everything up tonight. When I took the temp trap off I found some sand in my previously clean pipe. I suspect the plumber wad right - the concrete guys dropped some junk down the floor drain. Seems to drain alright, but it might cause issues down the road
 
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