Mystery Vent

[atrus5]

Hi everyone!

I decided to do a bathroom renovation and have run into a few plumbing vent issues I did not anticipate. I'd appreciate any thoughts and assistance with them.

1. When removing the tile around the whirlpool tub I found a capped vent in the wall. When the house was built (1993) I recall the plumbing inspector rejecting the plumbing because the whirlpool was not vented but then it was later approved. I don't recall any details beyond that but suspect this is related. The Whirlpool has drained fine for 30 years with no issues. The overflow has always been loud but everything has always worked. Out of curiosity I removed the cap on the vent and the whirlpool performed exactly the same. Any thoughts why it is capped (and not even glued)? It has always worked fine so I suspect just leave it alone except to perhaps glue it on to prevent any sewer gas from escaping - although none has ever been noted.

2. After removing the old one-piece shower unit (converting to a tiled shower) I see that the plumber took advantage of the seat area of the fiberglass shower unit to run the vent up and over an LVL beam before going up the back wall of the shower. Can I move this vent on the opposite side of the "nook" adjacent to the toilet? The wall is between and shower/toilet nook and a walk-in closet which are both in the larger bathroom area across from the whirlpool and double sinks. Running to the sidewall of the shower would require holes in the floor joists which are too close to the end so not possible. But any suggestions on vent placement are appreciated if I am wrong.

Additional detail:
- The shower & tub are on the opposite side of the bathroom from the sinks.
- The shower/tub drain follows the joist cavity to the end of the bathroom then runs along the house outer wall under the joists before returning up the wall the whirlpool and sinks are on.
- The shower vent is about 29 feet upstream of the whirlpool drain due to the wrap-around run.
- The sink vent is about 5 feet downstream from the whirlpool but I can't see how it is plumbed.
- The basement below the bathroom is finished with drywall including the ceiling.
- I dug through the attic insulation and only see vents from the shower and sinks which go pretty directly out the roof on this area of the house.

Thank You!

 

[MicEd69]

The P-trap in the "capped vent" photo is not per code as it isn't vented properly even if the vent went up through the roof. Need more pictures and dimensions before more suggested fixes can be provided. You kinda have a mess I'm afraid.

 

[atrus5]

Thanks for the reply MicEd69. I attached a diagram with dimensions. Hopefully it helps.

Appreciate if you could clarify why the vent is not proper even if completed through roof and any correction suggestions.

 

[MicEd69]

Here is a diagram showing the proper vent requirements for a P-trap.



The trap arm must be sloped 1/4" per foot, and ONLY a 1/4" per foot, between the trap weir and the vent. The vent needs to come off the trap arm vertically, or no more than 45 off vertical until it reaches 6" above the flood rim of the fixture in which it serves.

And note that the maximum trap arm distances shown can be slightly longer if you are under the IPC.

So, it appears that you may need to move the connect to the 3" farther downstream so that you can get the vent connected properly. But with the stipulation of no horizontal vent runs until you reach 6" above the flood rim of the fixture, the vent may not be able to be moved to the other side of the room. However, you can wet-vent via a horizontal line that is below the flood rim of the fixture. In other words, if you can drain a sink into that line and vent it properly, that vent will serve as a vent for the tub as well. The issue is that a horizontal vent line below the flood rim will/can fill with water and possibly collect "stuff". With nothing to flush that "stuff" out, it can cause a pluggage. Cleanouts are also an important item to incorporate in your vent and drain piping.

 

[Twowaxhack]

The trap arm must be sloped 1/4" per foot, and ONLY a 1/4" per foot, between the trap weir and the vent.

This is not correct.

1/4” per ft is the minimum and may be exceeded if the developed length is not maxed out.

Example: 2” fixture arm and trap with 3/8” per ft drop could have a developed length of 2’ and still be legal.

 

[MicEd69]

This is not correct.

1/4” per ft is the minimum and may be exceeded if the developed length is not maxed out.

Example: 2” fixture arm and trap with 3/8” per ft drop could have a developed length of 2’ and still be legal.

Yep, you are totally correct Twowaqxhack. I was only wanting atrus5 to understand that the vent cannot be in the 45-degree slope of his existing line. As atrus5 didn't understand that the vent was incorrect, I really didn't want to confuse the issue, so I used the recognized "standard" slope of 1/4" per foot for an 1 1/2" pipe.

Thanks for your clarification, Twowaxhack. This forum would be less intelligent if you were not on it.

 

[atrus5]

Thank you for the thorough replies. Please allow me some time to digest them.

In the meantime I need to clarify that in my original post I was referring to 2 different vents in the bathroom. Question 1 is for the "mystery vent" for the tub which you have been primarily responding to. Question 2 is for the shower vent which I want to confirm I can move. I apologize but my title of "Mystery Vent" was misleading since that is only 1 of the vents I am stuck on.

Here is a diagram of the entire bathroom with the 2 vent issues in maroon. Sorry, I realize the diagram is quite busy - the red are the room walls, blue the dimensions, and black the plumbing. I'm not sure how to represent these so... again my apologies.

 

[Twowaxhack]

The capped pipe in the wall is doing absolutely nothing but being a liability.

The tub isn’t vented, its a form of an s-trap and might have gurgled at the end of the tub draining if it was full of water. I’m sure it drained like a boss…..

The shower vent can be moved into any wall within 5’ of the p-trap (maybe further, check your code)


Consider getting a pro to do the work or study up on how plumbing vents and drains are installed. It’s not as random as it seems

The original plumber and inspector didn’t do a good job.

 

[atrus5]

Thank you both for your support. It is starting to make sense.


Also thanks for resolving Question 2. It will require some floor and drywall tear-up but I can do most work in the walk-in closet so not critical for appearance.


"It’s not as random as it seems." - The more I understand venting the more I truly appreciate this statement.

After researching how vents function and how the P-trap weir needs to "see" the vent it makes sense that a vent tapping into a Y will not work. Your discussion of 1/4 drop rate for 1.5" and 3/8 for 2" pipe (and length) makes sense as well.

I continue to consider a pro but with my wife telling me to "Leave well enough alone. It works fine now" has me trying to determine if any changes to the "mystery trap" will reduce the noise - which apparently only bothers me.

The noise starts immediately when a full tub starts to drain and it is air echoing through the overflow. It might change slightly when the tub is lower but with the tub removed I cannot check it. According to feedback to another individual in a different plumbing forum my noise is a sign that the drain is working real well and "they should tip the plumber". They even joke on ways for him to reduce the noise by partially obstructing the drain to slow it down.

Bottom line, I'm just the kind of guy that is bothered by things not done correctly... but maybe I should just move on.

I think that one option for the tub is to tie the vent into the horizontal pipe from the P-trap before it turns down 45deg to the 3" line. Obviously I would then have to finish the vent up through the wall to the attic. More drywall work but this time with blown-in cellulose I'd rather avoid. I'd have to check distances on the horizontal line to make sure I am the right distance from P-trap to vent to 45.

But I am starting to wonder if the wet vent MicEd69 mentioned is why my tub seems to work fine with great draining and the trap never sucked dry. There is a vent stack behind the closest sink which is about 42" downstream from the tub. The shower/toilet would help to keep the line clean and there is a cleanout. Concerns I have with this are two-fold
- I have yet to see a diagram of a wet vent with the tub P-Trap horizontal pipe above the 3" main line - in all drawings the horizontal from the P-trap IS the main line.
- The water closet should be the last on the wet vent. My toilet is not on the wet vent and it is serviced by the shower/toilet vent BUT it is still upstream from the wet vent circuit and poo passes through the wet vent section of pipe.

 

[MicEd69]

Perhaps this will help.

The tub is wet vented through the drain line from the sink. The toilet is also wet vented through the drain line from the tub and the drain line form the sink.

 

[atrus5]

Yes that helps a lot!

Now I'm wondering why he installed a dummy vent in the wall instead of doing it right and connecting the horizontal from tub to sink vent under the floor to create a wet vent. It doesn't appear that it would have been that difficult then (before the 3" drain was boxed in and drywalled in the basement).

I have read that wet vents weren't formally part of code for a while but I can't find when. Maybe it wasn't allowed 30 years ago.?

 

[Twowaxhack]

The guy that piped your tub drain didn’t understand basic plumbing.

 

[atrus5]

Like you suggested earlier, not happy with the plumbing inspectors as well. Rough-in inspection should have caught lack of tub vent. Final inspection caught the missing tub vent but then approved the bad "fix".


Anyways, thank you both for all of your assistance!! I really appreciate it.

 

[atrus5]

Final result for the whirlpool tub vent. Wife said no to tearing up the drywall ceiling downstairs for a wet vent so I tied into the sink dry vent instead.

Hopefully it's good enough since I stuffed the insulation back in today and i'm patching the drywall tomorrow.

If it's correct, you guys get the credit. If it's wrong I get the blame. Either way it's gotta be better than it was.

Thanks again to both!

 

[Twowaxhack]

Good job

 

[MicEd69]

Looks good!

 

[atrus5]

Now that the main part of the bathroom is buttoned up I'm starting on the 2nd issue I originally listed - The shower/toilet vent. If it's better to open a new thread please let me know.

I thought this would be easy but after cutting up the floor now I'm struggling to know the best way to move the vent and would really appreciate any suggestions on how to move it to the wall opposite where it is now.

To recap, the shower originally was a one-piece fiberglass unit with a built-in seat. About an inch forward of the rear shower wall is an LVL beam under the floor that the joists hang from. The original plumber popped out of the floor ahead of the LVL and 45'ed up and over it into the rear shower wall - this worked because a seat in the shower unit just barely provided clearance. Of course I didn't know this until the unit was cut out to expose it. Now the vent is in the way of installing a tiled shower. We don't want a seat there and honestly anything other than the original molded/curved seat would be too obtrusive.






The wall I want to move the vent into has a clothes closet on the other side so I could easily access the floor to cut it out if there is an advantage to accessing the pipe on that side.

The limitations for which wall the vent is run up through I THINK are:
- The vent can not stay in the wall it is in now since the LVL keeps me from running the pipe to there under the floor.
- The vent can not move to either sidewall of the shower without going through a joist and I am too near the end of the joist and too close to the top of the joist for a hole

Running the vent to the opposite wall between the toilet and the clothes closet is my only option, but,
- The vent can not be re-routed from where it plumbs in now without running horizontal (and quite a long way).
- Splicing the vent in directly below the closet wall would put the toilet between the shower and the vent killing the vent.
- Tieing the vent into the section of 3" just upstream of the toilet wye would require a horizontal run and options there are already limited since there is only 2 5"8" from toilet wye to subfloor.
- Moving the Toilet wye downstream under the clothes closet slightly would allow the vent to be under the closet wall but the toilet is already a tad high (changing the flooring so closet flange is 1/4" too high) and the longer run would raise the flange height.

Suggestions or corrections would be greatly appreciated!