Do Any of These Pipes Have Traps?


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Old 11-12-20, 04:57 AM
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Do Any of These Pipes Have Traps?

Home built in 1997. Poured concrete floor in basement.

There are 3 PVC pipes sticking up out of the concrete floor in the basement. All 3 are capped with glued-on PVC caps. One pipe is 1-7/8 OD, another is 2-3/8 OD, and the third is 4-1/2 OD. Which of these pipes has a trap already installed (in/under the concrete floor) one of them, two of them, all of them, or none of them? Please advise. Many thanks!

Pipes.
 
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Old 11-12-20, 05:19 AM
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Your pipes are 1 1/2", 2" and 4" by their inside diameter. The 2" might have a trap under the floor for a shower but looking is the only way to know for sure. The 1 1/2" pipe is for a sink while the 4" is for a toilet and neither will have a trap.

To check for a trap cut the cap off the end and pour some water down the pipe. If there is a trap you will see a puddle at the bottom.

You also need to look in the ceiling for a plumbing vent. That will be required to finish the bathroom.
 
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Old 11-12-20, 05:32 AM
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Thank you! That's very helpful. Much appreciated!

I want to run the drain (a garden hose) from a free-standing dehumidifier (placed on the floor) into one of the pipes. I know the pipe must have a trap. Must it have a vent?
 
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Old 11-12-20, 09:54 AM
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Sounds like a good use of one of those drains. You can always add a trap if needed - but use Dane's suggestion to see if one already exists.

Technically, yes, you need a vent... but for a dehumidifier drain I wouldn't worry much about it. It'll be draining slowly and won't cause any venting issues.
If it were a washing machine or water softener which drains water much faster, I would be more concerned and suggest venting properly.
 
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Old 11-13-20, 03:03 AM
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Thanks! Much appreciated. How should I go about removing the caps? Might it be possible to pry them off? Or, will they be solidly attached, and thus will require that I cut the pipe immediately below each cap?
 
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Old 11-13-20, 05:18 AM
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The caps are glued in place. Cut the top off.
 
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Old 12-17-20, 11:16 AM
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Per the suggestions given here (in the forum), I cut off the top of the 2" pipe. Then, I poured about 2 gallons of water into the pipe. I never saw the water "puddle" at the bottom of the pipe. Therefore, there's not a trap "within 2 gallons of the bottom of the pipe." However, I didn't smell any sewer gas nor anything that smelled like sewer.. nothing... no smell at all. This makes me wonder if there's a trap waaaaaay farther down the line.

Your thoughts?
 
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Old 12-17-20, 11:34 AM
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No, a trap cannot be located far away from the fixture. You likely will have to cut open the floor to install a trap.

Have you located the plumbing vent rough-ins?
 
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Old 12-17-20, 12:15 PM
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If you cut that pipe just below the cap and poured 2 gal of water, I doubt you would see a puddle from the trap. Take a washer or a ball of paper towel weighted with metal on string and drop it down the pipe. If it comes back up soaking wet, it's trapped. The trap might even be several inches away from the stand pipe.

edit...You might also take a snake and "feel" it going up and around the trap if it's there. I can't imagine installing those pipes for future use in a bathroom and not be trapped (at least for the large toilet pipe). What would be the point of putting it there without a trap and then needing to open up the concrete. Not saying it is there but?
 
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Old 12-18-20, 03:03 AM
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No, I never found a roughed-in vent pipe. But, I did find another pipe sticking up out of the concrete floor (in addition to the 3 pipes in the picture). It's another 2" pipe; about 8-feet from the 2" pipe shown in the image; lined up straight in line between the 2" pipe shown in the image and where the main sewer discharge (4" PVC) goes into the concrete floor. It appears to be a "second" location at which a shower could be installed. This (might) be odd, but I wonder if there's a trap in the 2" line... and the trap is located between the second pipe and the main discharge. ???
 
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Old 12-18-20, 03:49 AM
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This (might) be odd, but I wonder if there's a trap in the 2" line... and the trap is located between the second pipe and the main discharge. ???
I doubt it. Too much distance between them.
 
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Old 12-18-20, 10:05 AM
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No, the trap would be directly under the 2" pipe. It's either there or it isn't - in your case, it seems like it isn't.

I would set it up like a washing machine standpipe. Add a trap and a vent (I would just use a black Redi-Vent screw-on vent, about $8 at HD). If/when you do the whole bathroom, a proper vent will be required. But for a dehumidifier, it's worth the $10 in parts, but that's all I would do.

Setup like: (with a Redi-Vent on the right vertical pipe, at least 6" above the left pipe).

If in the future, you want to install a shower or sink, you can always cut all this out and pipe/vent it properly.

 
 

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