Venting Questions for Tub/Toilet Drains


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Old 07-26-10, 08:13 AM
C
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Venting Questions for Tub/Toilet Drains

Below is a pic of my existing drains. Ignore the red/blue lines, those were for something else. There are two toilets, 2 tubs and 2 vanities. The tubs and 2 toilets tied into the drain with no Tees to a vent. The drain on the left heading away from you is the 3" line that runs over to the wall and heads out to the septic. The one on the right parallel to it is a 2" line from one shower. You can just see in the top left a wye coming down, that is from one toilet. You can't see (out of the pic at the top) the other 3" wye from one vanity. At the bottom of the pic on the left of the 3" line you can see a trap. That is the 2" from the other shower and ties into the line coming from the left which is 3". To the left of that trap you can see another 3" wye coming down, that is the other toilet. Out of the pic on the left it transitions to 2", that is the other vanity. That vanity tees into ts own 2" vent. I suspect the 3" wye for the first vanity actually is 3" all the way up and is the vent for the rest of the fixtures, since none of them tee into a vent.

Question is, why do the toilets and tubs not tee into vents? I am guessing that it is a matter of distance to the 3" vent? Those fixtures are gone now as part of a bath remodel. I will be installing a whirlpool tub, a toilet and 2 vanities. The tub and toilet will be next to each other and will be installed more or less where the 2nd vanity on its own 2" vent was. That is, to the left in the pic. The linear distance would be about 4' to the main drain line, then another 8' back up the line to the 3" vent. The vanities will both be on the same wall where the 3" vent is now. So for the new tub and toilet, do I need to bring a 3" line up and over in the attic to the existing 3" vent? Or can they just be installed like the old fixtures were?

Edited to add I think they were using the 3" vent stack as a wet vent. When the house was originally plumbed there were no fixtures upstream of the 3" vent. Now there is another bathroom upstream of that.

 

Last edited by crokett; 07-26-10 at 09:36 AM.
  #2  
Old 07-26-10, 02:42 PM
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I wish you made more pictures and marked the pipes, it makes my head hurt trying to follow your description of how the pipes are run.

The only thing I can say is anything that has no vent with fixtures above has to be vented, maybe someone else can make better sense out of it then I can.
 
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Old 07-26-10, 03:07 PM
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Ok, doesn't look like I can edit a thread so.... here is the diagram labeled. Hopefully this is clearer. The existing fixtures are gone. The new fixtures will be two lavs, a tub and a toilet. One lav will use the existing drain you can't see upstream from where it says 'main drain'. The other will use what is now labeled tub drain. Those will be on the same wall and venting is straight forward.

The tub and toilet will be off to the left on the run where it says 'To Lav'. There is an existing 2" vent there. After doing some reading I think can tee the tub trap into a 3" line and then drop that down to 2" up to the attic for the vent. I will bring the 3" to the new toilet and it can wet vent back to the 2" vent. The length for the wet vent would be less than 18". Is this correct? The shower trap would be removed. The toilet drain above where it says 'To Lav' would also be removed.

 
 

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