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Thread: Which vent option is better?

  1. #1
    DIY Junior Member Louiep's Avatar
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    Default Which vent option is better?

    I am trying to put a band-aid on a few existing plumbing problems in my 100 year old house. I am adding the green venting in the picture below. The un-vented toilet is on the first floor and the other toilet is on the second. When you flush the toilet on the second floor, the un-vented toilet will bubble at times. I think that adding the Pink or the Orange vent will help with this a little, because the waste from the second floor will push the air out the new vent, instead of toward the sewer (and the un-vented toilet). I think Pink or Orange will work, but which seems to be the better choice?

    I know none of this is optimal, and I am sorry for the way it probably makes some of you cringe, but I really appreciate any insight that anyone can offer, so that I can improve the situation a little, at least.

    Thanks very much!

    Helpful Plumbing Hints for Residential Construction by Bert Polk Plumbing Inspector Lincoln County

    Last edited by Terry; 05-24-2010 at 03:22 PM.

  2. #2
    Plumber krow's Avatar
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    The way you are suggesting will do absolutely nothing except waste your time and money. You will not have accomplished anything.

    >the pic below will solve your problem or any variation of the new green vent position that I suggested.
    Attached Images Attached Images  

  3. #3
    DIY Junior Member Louiep's Avatar
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    Thanks for your reply krow. Perhaps you could explain a little more? Why would I vent the toilet after the fixture? Won't soil cause problems in the T or the Wye? Why did you leave my Orange vent in the picture? You indicated that those vents would not accomplish anything.

    The unvented toilet flushes fine. The problem is with the vented toilet. When it is flushed, it pushes air. Either of my venting options would remove 18 feet by 3" of air to push. After the soil passes the vent, the remaining air may cause a problem, but that is less likely b/c the pipe is horizontal. Am I misunderstanding? Will the Orange vent NOT be an easier path for the air than through the trap on the unvented toilet? If it is not an easier path, why leave it (as in your drawing)?

    I can see why the vent you added removes the problem from the remaining air, but isn't it problematic to vent after a soil fixture? I am asking that question in sincerity. A large part of the reason for my post was to learn more about that. I thought that I should maybe go with the Pink, to keep the vent away from the soil...

    Thanks again krow. Please share more of your knowledge if you are willing.

  4. #4
    Plumber krow's Avatar
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    Ok , As the water is coming down the vented stack on the left , the air will be pushed up the adijoining vent, as you suggested. It will also push air towards the sewer on the horizontal. Once the water passes the last vent in your original picture, air is forced through the sewer and ALSO up the second toilet drain to the right (hence the gurgling/bubbling) A large amount of water will create forced air in all directions.
    By placing the new vent where I suggested will allow the air to escape through the vent, releasing or diminishing the amount of air pushing on the lower level toilet bowl/trap . Each fixture has a p-trap (including a toilet that has it built into the porcelain). Each trap needs to be protected with a vent. In the event of a large flow of water(such as a toilet), air is forced forward and any opening to be found. At that point air would be forced in 2 directions: 1 towards the main sewer and the 2nd opening up towards the toilet. With the new vent present, the air will escape through the new vent instead of bubbles forming in the toilet.

    My drawing is a dipiction . You may want to use a Y. A "T" on a verticle toilet drain, usually indicates that the vent will also act as a drain as well as a vent (thats the term WET VENT)such as a sink drain. A "T" on the horizontal leg of the toilet drain is usually a dry vent. A "Y" fitting has less of a chance for anything to get caught at the inlet/outlet of that particular branch.

    So in your case, if you are not planning on draining anything into the new connection, it would be wise to use a Y

    I hope I made sense . I almost confused myself lol

    In any case, you would have to adhere to any codes relating to wet venting or dry venting including the sizing if piping for each paricular vent.

    Potentially you can remove a bit more of your proposed venting as shown below
    Attached Images Attached Images  

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    Moderator & Master Plumber hj's Avatar
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    You gave us options "A", or "B", but the correct answer is "C", None of the above. You have to vent the toilet NOT the pipe causing the problem. IF it were just a matter of relieving pressure the line going to the sewer would do that.

    Helpful Plumbing Hints for Residential Construction by Bert Polk Plumbing Inspector Lincoln County
    Last edited by Terry; 05-24-2010 at 03:22 PM.

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    DIY Junior Member Louiep's Avatar
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    Thank you krow for discussing it more, I really appreciate it.

    So now I just want to be sure that a Y (angled UP) is alright BELOW the toilet for a vent? I cannot vent the toilet properly, I understand this is a patch. But is it a patch that will be functional and not cause too many problems?

    hj, would you mind weighing in on this? It would help me out a lot.

    Thanks guys, I am grateful for the communication.

  7. #7
    Plumber jimbo's Avatar
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    You keep talking about the waste "pushing air" . That is not what happens. Every fixture in your house will drain perfectly well with NO VENTS AT ALL. This is how plumbing was installed originally, over a hundred years ago. Problem is, the movement of the waste creates a siphon, and lacking vents to allow air IN, then each fixture self-vents by allowing its trap to siphon dry, and thus resulting in ODOR. So vents are to allow air IN, to prevent trap siphon.

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    DIY Junior Member Louiep's Avatar
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    Thanks for your comment jimbo. So you are suggesting that when I flush the second story vented toilet, it is creating a siphon? And that the siphon is drawing air in from the unvented toilet on the first story? That is the bubbling that I am seeing?

    I am much more inclined to believe that the air is being pushed by the waste on the second story. The bubbling only happened sometimes, and can be reporoduced reliably if you add more water the bowl of the toilet upstairs, creating a more solid 'wall' of water plunging down the 3" stack, pushing air more effectively. My understanding has always been that vents allow air in in most cases but let air out at times too.

    I am reasonable and a quick learner, so if you can explain how the second story flush would make the first story toilet bubble b/c of a siphon, I would love to wrap my brain around it.

    Also, if you have a comment about venting a toilet with a Y below the toilet, like krow suggested, I would love to hear it. Thanks for the help.

  9. #9
    Plumber krow's Avatar
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    Vents are made to make the drains breath (for lack of a better word). To protect the p-trap from being syphoned and protecting the trap from releasing any forced sewer gases or air. The bubbling is caused by air pushing into the toilet. If and when it syphons, you will see the water in the bowl drop.

    I answered the question that you posed to me, the bubbling. These conditions happen with large volumes of water being discharged, such as a toilet, or even a sump pump that had been installed on an unvented drain line. They will push the air as well as draw it in, such as your diaphram in your chest. It breaths
    Such cases DO NOT ALLOW THE AVV's to function like a normal vent would. (open to the atmosphere)

    A Y will work fine for what you need to do.. It will stop any solids from entering the branch, unless the pipe/sewer gets plugged for other reasons.

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