Siphons on drains

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Dwitting87

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I had one of these eureka (or maybe oh S#@$) moments about how some of the vents are set up in my house. I was curious if anyone could confirm my suspicions:

Vent A: This vent has a 1.5" shower drain coming out of the first floor into the basement with a P trap that ducts into a Tee. Is this little "dip" at the end going to cause a siphon? Should I be concerned?

Vent B: This one is much more obvious to me. There are two attachments that both enter on Wyes. I suppose I'm not sure what the rules are for toilets, but the shower seems suspect given the 4ft diagonal pass to the sanitary Wye connection.

Does anyone have any insight for either of these? Is there any relatively straightforward solution is so? BTW I've added a photo attached.


I should mention that Vent B is behind a wall (with access, but not much).
 

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Stuff

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Someone did not know what they were doing. If this is a sample of your plumbing what else is wrong in you house?

First one can be fixed by lowering the trap if you have room. 2nd one requires a redesign as toilet should not drain over anything unvented.
 

Dwitting87

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Hi everyone,

I think one thing I forgot to clarify here is that the middle verticals actually extend upward and are the vents for the stack. That being said, I have a few follow up questions:

1. It was mentioned that the toilet is emptying into the vertical above the shower. Is that wrong? (or does the fact that I forgot to mention it's vented nullify that comment?)

2. hj, You mentioned they are S traps. My house was built in 1979 (and to stuff"s comment, yes I find things wrong daily in this house...oh the joys of being a newbie homebuyer). From my limited reading on this site, it sounds like S traps are no longer allowed, but were sometimes installed years ago. Should I bother fixing this or leave well enough alone? I'm not looking for a project, I just want to make sure I don't have a major issue on my hands.
 

Dwitting87

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OK. I realized I misunderstood the comment about venting (i.e. before entering the waste stack). My apologies.

I have attached what I believe is the correct fix for the issue (HJ, I actually stalked some of your comments on similar issues and found this to be the recurring suggestion). Using a side attach, I should be able to extend the trap arm of the shower to run parallel to the w.c. and install on the side. Should I use a long turn 90 for this final connection?

I also showed using 2 metal ferncos to install the final piece when these are all in place. I have tried slip couplings with a friends house before and found them to be a nightmare. I believe these are fine correct?


Just to keep this interesting, I thought I would ask the following (just to explore). If I wanted to put a sink in the basement (all of this is 1st floor bathroom crap I'm dealing with in the basement), would it be allowed to have it after the toilet provided it taps the wet vent above the toilet?

I've seen comments about doing this with dry vents. I wasn't sure if the wet vent made a difference.



Thanks everyone! This has been educational.
 

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Dwitting87

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The shower can be plumbed either above the toilet, or on a side inlet.
Not below the toilet.
The shower should be 2".


Hi Terry,

Yes, that is what I was proposing to fix it (as crudely drawn in the pic). I apologize I didn't know the best 2D way to show a side attachment (just the text).

Just to be exhaustive, is the use of a wet vent that is Tee'ed off above the WC an acceptable way to vent a sink that is waste connected BELOW the WC (as in picture)?


Thanks for the help friends.
 

Dwitting87

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Plumbing issues-wet vent for basement.png




Hi Terry,

I understand the 6" revent comment. To clarify the second comment, would any wet vent meet the 42" requirement you mentioned? I've added a simplified photo for example. Are you saying that even a wet vent attachment would need to be 42" above the next floor up (my guess something to do with the height of sinks and whatnot)? I only ask because it would seem that would just make it a normal vent (if above everything at that point).
 

Terry

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I'm trying how to explain how to get your permit passed off. You can fudge and see if the inspector notices, but isn't that a waste of time if he makes the trip out and turns down the permit?
 

Dwitting87

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I'm trying how to explain how to get your permit passed off. You can fudge and see if the inspector notices, but isn't that a waste of time if he makes the trip out and turns down the permit?


Hi Terry,

I apologize, I wasn't trying to contest the logic, just understand. I think what I misunderstood at first is that a wet vent is interchangeable with a dry vent.

From your comment, it sounds like the only way I would be able to install a sink in the basement is with a vent tie in on the first floor at 42"(at that point I would just tie in above the sinks on first floor) and then shoot it down to the basement for this sink.
 

Dwitting87

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Do you know about AAV vents?


Lol yes, but enough time on this site has brought me to believe that's a four letter word. I figure best to hear about the right way first. Eventually there is another area in my basement I would like to look at putting in a bathroom. I know that one will likely drive me to a tied in vent. I figure I should probably just learn about the right way i.e. the way that doesn't have cycle life like a vent.
 

Reach4

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I am not a plumber. What follows is my interpretation.

If you were to run a 2x3x3 santee into a 3 inch drain and disallowed wet vent from above, I expect it would work fine (but I could be wrong), but not pass inspection. If you used a combo in the trap arm with an AAV up, it would pass inspection. If you put an AAV on a long sweep followed by a san tee in the 3 inch, it would work if the AAV failed closed. I don't know if that would pass if you used the santee rather than the combo.

So what I am saying is that maybe you could find something that passes with an AAV but would also work in practice if the AAV failed closed. If the AAV fails open, it is going to stink.

To have it all, you have to bring the vent down from above the first floor flood level, put a 2 inch combo (or similar) between the vent and the trap arm, and another 2x3x3 combo in the 3-inch pipe.
 
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hj

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A "wet vent' becomes a 'dry vent' above the fixture that is creating the "wet". In other words, the ONLY "wet vent" is the portion below the sink connection, the part going up, that you call a wet vent is really a "dry vent" since it NEVER has water flowing through it. ALL vents have to connect at least 42" above the floor OR 6" above the overflow level of the fixture whichever is HIGHEST.
 

Dwitting87

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A "wet vent' becomes a 'dry vent' above the fixture that is creating the "wet". In other words, the ONLY "wet vent" is the portion below the sink connection, the part going up, that you call a wet vent is really a "dry vent" since it NEVER has water flowing through it. ALL vents have to connect at least 42" above the floor OR 6" above the overflow level of the fixture whichever is HIGHEST.


Hi HJ, thank you for the clarification. Just to elaborate, I called that a wet vent because upstairs there is a sink that feeds it. Per Terry's comment, it seemed like I couldn't tap between the sinks upstairs and the toilet. i.e. I can't use a wet vent to allow a connection below a toilet.

Did I interpret that correctly?


And to other comment, I looked the best way to bring a vent down to the basement. Because I have a double vanity in the bathroom overhead, so I would probably have to tie it together in the attic and then shoot a line down (otherwise I would have to cut through an entire wall worth of studs...just doesn't seem structurally sound). Sound right?

Plumbing issues-wry  vent for basement.png
 
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Terry

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Wet venting is for bathroom fixtures, located on the same floor.

Washers, Kitchen sinks, Laundry trays don't get included. Any venting done on one floor, needs to go up a floor to the revent above those fixtures.
What I somtimes notice going into homes plumbed kind of iffy, are things like, flush a toilet upstairs, and the water in the downstairs toilet goes up and down and sloshes out water from the bowl.
I've seen washers siphon kitchen traps. Bathroom lavs that slowly drain down the other bowl as the companion bowl is being used. I've seen some funky things.
 

Dwitting87

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Wet venting is for bathroom fixtures, located on the same floor.

Washers, Kitchen sinks, Laundry trays don't get included. Any venting done on one floor, needs to go up a floor to the revent above those fixtures.
What I somtimes notice going into homes plumbed kind of iffy, are things like, flush a toilet upstairs, and the water in the downstairs toilet goes up and down and sloshes out water from the bowl.
I've seen washers siphon kitchen traps. Bathroom lavs that slowly drain down the other bowl as the companion bowl is being used. I've seen some funky things.


I think I finally got it Terry. Thanks for your help (and HJ). By the way I added an image showing what I was thinking. I think it sums up what you said.
 
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