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Thread: Help venting small bathroom in basemment

  1. #1
    DIY Junior Member rcdba's Avatar
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    Default Help venting small bathroom in basemment

    I am currently adding a bathroom to the basement. It's a small bathroom 4 x 6 feet. Are my vents correct ? Keep in mind my vent for the toilet and shower connections are going to be sanitary-Tee's or Wye's laying on its back.

    I have two options for the shower vent. Do I run it to the back wall and up or should I run it to the left over the soil pipe and up?

    The sink will be a wet vent. When connecting to the 4 inch soil pipe, will I need a sanitary tee or wye to on its back or can i put it on its side?

    Do I need a vent for the toilet ?
    Is it better safe than sorry and vent everything ?


    Any help is greatly appreciated.

    Richard
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  2. #2
    In the Trades Tom Sawyer's Avatar
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    No part of the vent shall be horizontal until 6" above the flood level rim of the highest fixture which is the lav so.......no
    [B]No, plumbing ain't rocket science. Unlike rocket science, plumbing requires a license[B]

  3. #3
    DIY Junior Member rcdba's Avatar
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    my vent will be horizontal above flood level rim of sink. this is where the toilet and shower will vent to, then vent to 2" vertical vent ?

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    Nuclear Engineer nukeman's Avatar
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    How will you get the vents to the outside wall without going horizontal under the floor? Are there walls next to the shower and toilet that you aren't showing?

    What Tom is saying is that those vents need to be taken off vertically (>45*) and continue up until >6" above the lav (around 42"), which you cannot do in your layout unless there are some additional walls in the room that you are not showing. Once above 42", they can go horizontal and tie together. Usually, the best way to vent a bathroom group is to wet vent through the lav. You could run the lav in 2" and connect it into the shower line (also 2") to vent the shower. This would then continue to the toilet connection to vent the toilet (3" line would be fine here, but 4" is okay too). From the lav (going up), you would have either 1.5" or 2" vent (depending on what is required in your location) and that would continue through the roof (or tied into an existing vent connection in the attic). Some colder locations require you to step up to say 3" or greater when going through the roof to prevent frost from closing up the vent in the winter.

    Without pics or being there, we can only say what will work from a general point of view. The best layout and what will actually work there depends on many factors that we cannot see (existing plumbing, location of joists/blocking, heat runs, etc.).

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    Moderator & Master Plumber hj's Avatar
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    what do you mean by ""the sink will be a wet vent"? Your drawing does not indicate that. You appear to show the shower and toilet drains with horizontal vents under the floor, which is not permitted. What is the yellow line?
    Licensed residential and commercial plumber

  6. #6
    DIY Junior Member rcdba's Avatar
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    was planning to go horizontal under the floor with a wye on its back then up into the wall with a 90 degree to meet the sink. There will be a wall behind the shower toilet and sink. This is behind the blue outline of the room. Below is what I planned to put behind the lavatory and toilet, then this goes up to the vent.

    So I can get rid of the vent (#1) going to the toilet then go up with the yellow vent to the roof? Name:  ventinwallB.jpg
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    thanks
    Richard
    Last edited by rcdba; 01-08-2013 at 06:39 AM.

  7. #7
    Nuclear Engineer nukeman's Avatar
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    You can't do that. You can't run dry vents under the floor (or have them horizontal any place lower than usually 42"). However, a wet vent can be horizontal since it is washed by a fixture. This is why bathroom groups are typically wet vented as it can be difficult to otherwise vent showers and toilets without putting additional walls in the room.

    The other way to do it (using dry vents) is to run the fixtures to the closest wall and take your vents vertically there. However, there are limitations on how far you can go before venting, so this option is not always practical. Wet venting is usually much easier and will usually use fewer fittings and less pipe to get the job done.

    You should search a bit more and see some layouts of what others have done and see if you can get the idea of wet venting. Many think that sticking a vent in the side of the main line will vent it, but that is not the case. Each trap needs to be vented and a dry vent can't be horizontal until above 42" (usually) (no running it under the floor).

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    DIY Junior Member rcdba's Avatar
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    I appreciate your knowledge and guidance in regards to plumbing. I understand you can't have a horizontal vent under the floor. How about a vent 45 degree with a 4 x 2 wye a bit further down and end up vertical in the wall cavity. Is this still considered horizontal. Then I could have the shower discharge into the vent. Please look at the drawing.

    Name:  venttoilet.jpg
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    thanks,
    Richard

  9. #9
    DIY Junior Member tireiron's Avatar
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    Not a pro but this might help. Depending on your code but it should be easy on such a small bath. Run the 3" pipe to your toilet from the main using a y connector (assuming horizontal branch). Branch off using wye or wye combo (rolled?) 2 inch to your lavatory and wet vent the other fixtures from the lav using 2" up the wall. Then branch off to your shower using wye or wye combo being careful to keep within the 5 foot distance for 2" branch.

    Two inch drains (shower) can be 5 feet from their vent which in this case would be a wet vent at the 3". With some planning you can keep within those distances for the shower. The lav would is vented up the wall behind it using 2x2x1.5 sani-T. The toilet and shower would be wet vented. All this is done while maintaining proper pitch whic means when planning be sure to run the longer lines (shower?) first when dry fitting to see where things line up.
    Name:  small bath1.jpg
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    Last edited by tireiron; 01-08-2013 at 10:27 PM. Reason: edited drawing

  10. #10
    Nuclear Engineer nukeman's Avatar
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    tireiron: The shower is not vented in your drawing. The toilet flushing will pull water from the shower trap.

    rcdba: If the vent is at 45*, that could work okay. However, 45* is much steeper than what you show. The toilet flange is normally 12" from the wall. If you take the vent off at 45*, the pipe will come up in the middle of the floor before reaching the outer wall (unless your plumbing was placed much lower than usual). What you can do is take your drawing and modify it a bit. That red line could be 2" coming from your lav drain. At that point, it is a wet vent and no longer has to be above 45*. You then tie in the shower to that line to vent it and then continue to the toilet line. Now, everything is vented at that point. Essentially, you would do something like tireiron shows, but the shower would connect to the lav line before the lav line connected into the 3"/4" line.

    Good luck.

    I would probably use 3" for the toilet line (unless I had 4" on hand). All the fittings under th floor will be either long radius elbows, wyes, combos (or wye + 1/8 bend). No santees under the floor. You will have a santee in the wall behind the lav with 2" going downward for the drain and 1.5" or 2" going up for the vent.

  11. #11
    Moderator & Master Plumber hj's Avatar
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    quote; Two inch drains (shower) can be 5 feet from their vent which in this case would be a wet vent at the 3

    I am glad you prefaced your suggestion with the caveat that you are NOT a plumber, because in your drawing the shower does NOT have a vent so it is NOT 5' from the vent. You also cannot have a major fixture, such as toilet, flowing past the connection minor fixture, such as a shower, if the minor fixture does NOT have its own "dedicated" vent. If you run the shower to the lavatory drain, you have to make sure you do not create an "S" or "3/4 S" trap.

    The real problem is that like many DIYers, you believe that anyone can be a plumber as long as they buy enough fittings and pipes then stick them together so the water flows downhill.
    Last edited by hj; 01-09-2013 at 07:07 AM.
    Licensed residential and commercial plumber

  12. #12
    DIY Junior Member tireiron's Avatar
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    I stand corrected. As nukeman describes if you can connect the shower to the lav drain (within 5 feet) that would wet vent the shower using the lav. Might be able to do that in the small footprint you have. Name:  Small bath.jpg
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  13. #13
    Nuclear Engineer nukeman's Avatar
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    If you are under IPC, you can run up to 8' on a 2" line before the vent. However, I would go with the UPC limit of 5'. With IPC, they figure 1/4" per ft slope, so after 8', you can dropped one full pipe diameter on a 2" line. The reason why this drop is important is that you will effectively develop an S-trap (or 3/4 S-trap..whatever you want to call it) if you exceed this distance. With UPC, they limit to 5' to give some margin is being away from making an S-trap. Also, since it isn't likely that your slope will be exactly 1/4" per foot, using the 5' limit gives some wiggle room.

    Also, don't get hung up on a certain layout. Sometimes changing an angle of a drain or moving things around in the bathroom can make the plumbing easier and cleaner. Like I said eariler, it is difficult to say what is the best layout without being there. There may be a much better way to do it. It may be worth getting a plumber out there to lay everything out. Perhaps you can help with the grunt work (digging, etc.) to save some cash.

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    DIY Junior Member rcdba's Avatar
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    I thank all of you gentlemen for your help. I'm going with your suggestions to vent from the lavatory. It's a more ideal option because I have no space to add another wall anywhere.

    I do have another quick question before I start roughing in this small bathroom. Is one able to pipe a toilet in the opposite direction of a sewer line and curve at some point to go the direction of the sewer. I would be using a combination of 1/4 bend, 1/8, and 1/16 bends. (or a long sweep?) Or should I run it straight back with a wye in the opposite direction. This bathroom will be under a set of stairs. A great way to use a dead space. Please look at the image.

    Name:  curved toilet.jpg
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    Thanks again,
    Richard

  15. #15
    Test, Don't Guess! cacher_chick's Avatar
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    I would run the water closet drain directly towards the main line, and vent it through the lav. The shower drain can bend toward any of the 3 walls to be vented before it meets it's own wye connection to the main line.

    If you place too many bends in any drain line, you will be required to add accessible clean-outs.

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