Is this a siphon trap?

[jpap]

I'm planning a remodel underneath two bathrooms (photo is looking at the upper bathrooms from below).

It looks like tub trap arm is wet vented by a 2" wye going straight up to the lav above. That lav has a 1-1/2" dry vent on the upper level (and no other fixtures on the same 1-1/2" dry vent).

Should I be concerned about water rushing down from the lav siphoning the tub P-trap? Or is this a pretty standard wet-vent (CA under UPC)?

 

[jpap]

Reading this article, with its main diagram repeated below, it looks like the tub wet-vent might not be proper here?

Do I need to turn the wye on its side, so that the lav enters 45 deg (or less) from the horizontal? (That's the bottom-right situation in the image below.)

Could I instead raise the tub P-trap and use a san-tee to connect to the vertical part of the lav drain before it enters the wye?

 

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[Jeff H Young]

thats a verticle wet vent . I think it complys but if not I see no reason it wont funtion perfect. its alreadsy built So I dont see a reason to change. bath tub shall be as short as practicle So a really C.S. inspector could argue its sort of a general workmanship issue and a little better planning might have been able to provide a shorter tailpiece at tub but I think generaly it looks ok sure wouldnt worry about it unless may bey you are getting it inspected even then I think itll fly fine.

 

[John Gayewski]

If the pipe is 2" it's good.

 

[jpap]

Thank you for your replies, Jeff and John. The wet vent is 2" until the 1-1/2" dry vent above it.

My main concern is whether the high velocity of waste from the lav would siphon the tub p-trap. The tub is in a guest bathroom and will rarely be used, while the lav is in a main bathroom that will be used every day. What do you think?

On code-compliance, this situation looks similar to this thread from 2020 where @wwhitney wrote:

...some people say the wye has to be flat, although I don't find any support for that in the text of the IPC or UPC

The JLC article previously linked is the only reference I could find that explains why one would want the wye to be flat.

I can probably live with a slow tub (shower) but I definitely want to avoid sewer gasses in the house. (We're yet to move in, so I don't know if this is a real problem.)

 

[Jeff H Young]

Sorry I said anything befor its fine its a VERTICLE wet vent no the combi dosent need to be flat forget it enjoy a stink free and safe life. its not a problem

 

[John Gayewski]

No there's no problem, the engineering has been figured for us as it's code compliant. A verticale wet vent (in this case being 2") has been sized in the code to leave room for air. Unless the water is dropping for the second story there's no issue.

 

[Jeff H Young]

this is a built house and looks fine the vent is wet from a lav right there its all good ! JPAP I think read something and got worried