I have a question concerning the plumbing in my basement. We are finishing our basment and adding a bathroom. In the concrete floor, there are 3 pvc pipes already roughed in. 2 small ones and a big one in the middle. I am assumming the large one is toilet, the small ones are shower and sink? Do I assume that they are properly vented to the main drain under the concrete? There is a stack a couple of feet away that goes through the ceiling to the roof.

Only 3 pipes sticking up through the floor doesn't sound like enough pipes to do what you want.

One of the smaller pipes is likely the vent for the toilet, while the other is likely intended for a lavatory.

The groundwork was probably intended for only a half bath.

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Originally Posted by iamgrowler

Only 3 pipes sticking up through the floor doesn't sound like enough pipes to do what you want.

One of the smaller pipes is likely the vent for the toilet, while the other is likely intended for a lavatory.

The groundwork was probably intended for only a half bath.

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Thanks for the response, that makes sense, how do I know for sure?

Hey Casey,

Growler's assuming that your code calls for each fixture to have a individual vent. Not all codes call for that. The code in the Tampa Bay Area don't.
Let me give you my take on your rough in, depending where the pipes are located.
The big pipe picks up the toilet. If one of the pipes are in a wall, or where you plan to place a wall, then that picks up the lavatory and if the last pipe sticks up out of the floor then that picks up the shower.
You ask, "Do i assume that they are properly vented to the main drain under the concrete?"
You may not assume the group's vented. Thy lavatory must have its own vent that runs through the roof or revents back into a existing roof vent.
You may not tie the vent back to the stack in the basement.
Now about venting. Your best bet would be to call the plumber who roughed the job in but if this was installed in my area here's how it would play out under the slab
Toilet connected to the main sewer. Lavatory connected to the toilets drain line and the shower's connected to the lavatory drain line.
The lavatory's vented through the roof. The toilet and shower are wet vented through the lavatory vent. Thus one vent services the entire group.
Again, this is subject to local codes. Growler works off one set and I work off another. I like mine better. Growler thinks you were roughed for a half bath. I think you were roughed for a three fixture bathroom group.
It will be interesting to find out who's correct. Please keep us in the loop on this. Regards, Tom

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Originally Posted by CaseyB

thanks for the response, that makes sense, how do i know for sure?

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Pour a bucket of water down the two smaller pipes, if one of the 2 pipes has visible standing water at the bottom of it (you may need a flashlight to see if it's very deep).

If there is standing water in the bottom of one of the pipes, then Tom is correct, the one with water remaining in it is trapped and is likely the intended shower drain, while the other is the lavatory drain and combination vent for the other fixtures.

If both of the smaller drains flow through with out any water standing in one of them, then it is plumbed for a half bath.

If you tell me which state you are posting from, I can tell you which plumbing code your state has adopted.

To answer speedball, all 3 of the pipes are located in front of where the wall will be, once the wall is put up , they will all 3 be in the ground in front of the wall.

To answer growler, I am in Alabama.


I have a plumber coming out to look at it this week, so I will let you know what they say,
I appreciate the help!

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to answer growler, I am in Alabama.

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Sounds like Tom nailed this one.

Most of Alabama has adopted the 2003 International Plumbing Code.

The plumber hasn't come yet, but we found pictures they took when they built our house that shows the layout of the pipes,(pretty neat) I attached a rough sketch of the layout.
It appears none of the pipes have a trap, and they all 3 run straight to the main drain underneath the basement floor. What can be done with this setup? I am assuming if none are trapped, I would have to tear up concrete in order to trap for the shower, and I would have to just do a half-bath if I didn't want to tear up concrete? Am I correct that the toilet has a trap in it? Once again, pardon my ignorance on all of this, that's why I am asking the experts!

Thanks,- Casey

Wanted to add on more thing. The plumber just called me, he looked at the picture I had for him and he said that this was an illegal setup and he would have to rip it all up. He said that since the toilet flushed past the other 2 pipes the suction would suck the traps dry and he had to re-plumb it all under the concrete. Does that sound right?

Is there a way to tell all that with out ripping the concrete out? He is basing all of that off the photo, which was taken before the concrete was even poured. Who's to say that was even the final layout, it was 20 years ago.

Can you upload the original photo?

I don't have it scanned. I can do that tonight and upload it.

Hey Casey,

"the plumber just called me, he looked at the picture i had for him and he said that this was an illegal setup and he would have to rip it all up. he said that since the toilet flushed past the other 2 pipes the suction would suck the traps dry and he had to re-plumb it all under the concrete. does that sound right?"

If the drawing you posted is correct and all the pipes are in a line then the cement would have to come up any how. The big pipe wants to be 12 inches off the finished wall. One of those smaller pipes wants to be in the wall to stub out for a lavatory and to run up to the roof for a vent. The other needs to come out for a vent to tie back to the lavatory vent and a trap to pick up a shower if you wish to have one installed.
Your plumber was only half right when he informed you that he had to rip out the plumbing because the toilet discharged past the smaller pipe.
While it's true that you can not discharge a major fixture,(toilet) past a unvented minor one (tub, lav, or shower), however, if the minor one is vented then it's perfectly acceptable. If the pipes were positioned properly all you would have to do is add a trap and raiser for the shower.
Like Growler, I'm interested in seeing what the picture will show. Regards, Tom

I poured water down each of the pipes like you said, and water stayed in each of them. So that means they all have a trap, right?

If that's the case,I should be all right, as long as I vent them, correct?

Good morning Casey,
"i poured water down each of the pipes like you said, and water stayed in each of them. so that means they all have a trap, right?"

There should have been water in only one of them, (the shower). However, if they're all lined up in a row then they will have to be repositioned anyhow.
The picture will help us to sort this out. Regards, Tom

I couldn't get my old busted scanner to work so I can't upload the old picture. The pipes are all 3 in a line 16 inches away from the cinder block. That would make them about 12 in. off the finished wall. Water stays in the far right one when you pour it in. the middle one for the toilet I didn't check. There was no water in the far left one. How can this be utilized without tearing up the concrete? Anything possible?

That is just dandy for the toilet stub -up but the lavatory stub-up should have been in the wall and the shower should have been placed well away from the toilet so you could either install a custom tile or manufactured shower. Figure out your fixture positions and we can help with the rest. And get that scanner fixed. As we get deeper into this we're going to need some pics and fixture layouts. Regards, Tom

Well I was going to put a vanity and lavatory on the far left, and I think a manufactured shower unit will fit on the right, even though it will put it close to the toilet. My thought was that since the pipe for the lavatory was out from the wall, it could be concealed in the vanity and the vent could run out the back and up the wall. Make sense? I guess I am confused about venting the toilet and shower?

All right, finally got a picture, so ignore all my previous ramblings. In the picture, you will see the layout. To the far right of the picture is where the main waste stack comes down from upstairs. I am wanting to do a lavatory on the far left , toilet in the middle, and shower on the right. I poured water in the far right pipe and it remained in the bottom. When I opened up the far left pipe, it was dry initially, but water remained in the bottom when I poured water down it. So I guess it is trapped also? The red lines I added is what the layout appears to be under the concrete based on an old pre-construction picture(which I couldn't get scanned).

I would appreciate your recommendations on what can be done with this setup, (without tearing up the concrete, not in my budget or time frame right now). Need advice on how I can vent these fixtures.
Thanks in advance.

Only one of the pipes should be trapped. Here's how to tell which one. Take a stick and run it down to the base of the curve. The pipe that's trapped will have the most amount on the stick. If a elbo, there will be very little water on the stick. If a trap, the there will be a few inches on it. If both lines are trapped you have a problem. One will have to be removed to install a lavatory. You can not double trap a fixture. Also we're going to hafta get real creative to vent the shower. I don't see any way to avoid breaking up the pour.
If the shower drain had been connected to the lavatory drain then the shower would have been wet vented. The plumber who roughed this didn't do you any favors. Regards, Tom

That's what I was afraid of. I just checked with a stick and I measured 4 inches of water in the bottom of each pipe.

Concerning the shower, I was visualizing framing the wall out further so the far right pipe was in the wall. Then venting that straight up and running the drain along the floor. I would build a platform to raise the shower unit off the ground so the drain line could run under it and get over to the drain pipe that has the trap in it, which would now be behind the wall. Would that work? If so, would that vent also take care of the toilet?
Just trying to visualize something out of my crazy setup.

What does the expert think?


Thanks in advance