Where does the air vent go in this case? aka do I need a second AAV? aka drain gurgling issues

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Sokolq55

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Whenever my laundry pump drains, there’s gurgling from the downstairs shower p trap. There is no gurgling from the kitchen p trap.

There is already a vent as seen in the picture and I can see the spring mechanism activating when the laundry pump is draining. The laundry pump itself has an open stack vent that’s not blocked.

Is the current vent in picture not enough?
Should one be installed dedicated just to the shower drain? And if so, where would it go? ie closer to the shower p trap or extended up like I drew in yellow?

thanks!

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wwhitney

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Every fixture needs a trap, and every trap need a vent attached to the trap outlet before the trap arm drops more than one pipe diameter. So the kitchen sink trap vent will be above the floor, and the shower trap vent needs to be nearish the shower p trap, not at the location you drew.

Can you provide a picture of the shower p-trap and the piping to the first picture? Also, what is your laundry pump and can you provide a picture of it and the piping to the first picture?

I'm not familiar with laundry pumps, so maybe the AAV in your picture is how they get vented. If your shower trap isn't properly vented, that could explain your gurgling.

Cheers, Wayne
 

Sokolq55

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Every fixture needs a trap, and every trap need a vent attached to the trap outlet before the trap arm drops more than one pipe diameter. So the kitchen sink trap vent will be above the floor, and the shower trap vent needs to be nearish the shower p trap, not at the location you drew.

Can you provide a picture of the shower p-trap and the piping to the first picture? Also, what is your laundry pump and can you provide a picture of it and the piping to the first picture?

I'm not familiar with laundry pumps, so maybe the AAV in your picture is how they get vented. If your shower trap isn't properly vented, that could explain your gurgling.

Cheers, Wayne

Thanks, Wayne. The problem with the shower is it’s on a slab - ain’t much access to place a vent before the trap drops. It would have to go someplace after.

Thank!

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Sokolq55

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This has always been this way. We did have a main backup before but at that time pretty much everything started gurgling and even after the main was cleared, the shower continued.
 
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James Henry

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I suspect, because you don't have a vent for the shower, when the washer drains the soap bubbles push air up the shower drain and disturb the trap seal.
 

Sokolq55

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You need a vent to the open atmosphere. Placing the AAV will not help you. AAV let’s air in to the system, not out. You have air wanting out of the system.

Where would placement of said vent be optimal? Closest to the shower p trap? I was thinking maybe one right out of the clean out near the shower.

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Reach4

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Where would placement of said vent be optimal?
The top end would be above the roof.

Do you have a roof plumbing vent? What does that vent?

If you have no shower vent, and that shower pipe is coming horizontally from the shower trap, for an AAV to be useful, it would have to be before the shower trap output turns down. If close enough, an AAV would be up near the tip of your yellow arrow. Max distance would be within 8 ft of the U of the trap.
 
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Sokolq55

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You need a vent to the open atmosphere. Placing the AAV will not help you. AAV let’s air in to the system, not out. You have air wanting out of the system.

I actually just double checked with some dish soap water over the drain when the gurgling happens - the bubbles actually get sucked in.

My theory is that when the laundry water rushes down past the shower wye it creates a vacuum that pulls the air out through the shower drain.
 
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Sokolq55

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The top end would be above the roof.

Do you have a roof plumbing vent? What does that vent?

If you have no shower vent, and that shower pipe is coming horizontally from the shower trap, for an AAV to be useful, it would have to be before the shower trap output turns down. If close enough, an AAV would be up near the tip of your yellow arrow. Max distance would be within 8 ft of the U of the trap.

This shower was a retrofit of a bathroom with no shower by past owner. The new drain from the shower basically bypasses the main stack vent which is behind the toilet and the shower is on opposite end and on a slab. So I suspect they just didn’t want to break up the slab to hook into the main vent.

Will try your suggestion and put in an AAV near the tip of the yellow arrow I drew. Basically as close to trap as I can get it. It’s only like two feet between the arrow tip and the trap with very little drop.
 

Reach4

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I actually just double checked with some dish soap water over the drain when the gurgling happens - the bubbles actually get sucked in.

My theory is that when the laundry water rushes down past the shower wye it creates a vacuum that pulls the air out through the shower drain.
Good test and analysis!
Will try your suggestion and put in an AAV near the tip of the yellow arrow I drew. Basically as close to trap as I can get it. It’s only like two feet between the arrow tip and the trap with very little drop.
Nice. If you have room, great. If there is not room, you could cut the pipe at the s in first, and replace more.

Wherever is handy between 4 inches and 8 ft. ;-)

You could put a sanitary tee to transition the shower drainage from vertical to horizontal. Put the AAV 4 inches above the santee, and drainage comes out of the bottom of the santee.

If using a different fitting to introduce the vent, show us your plan first. You could tilt the santee. The aav can be with 15 degrees of true vertical. The santee could tilt up to 45 degrees.
 
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wwhitney

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You could put a sanitary tee to transition the shower drainage from vertical to horizontal. Put the AAV 4 inches above the santee, and drainage comes out of the bottom of the santee.
This option right here, I just want to second that. The downstream most allowable place for the AAV is to replace the elbow just above the text "From shower" with a san-tee, and put the AAV on the top of the san-tee.

Cheers, Wayne
 

Sokolq55

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The pump for the laundry has an atmospheric vent. It’s the vertical pipe extending from the pump basin on the left.

You could eliminate All the AAV’s by piping all your vents to that vertical vent.
This would equalize the entire system without a mechanical device.

I don’t know if that would work because that vent doesn’t go anywhere - it terminates at basement ceiling and would be below the p trap of the shower drain. Plus I’d have to run a new circuit to it. I hear you regarding eliminating mechanical parts - if I were to redo this bathroom I’d connect the shower and the sink via a wet vent to the main stack. But for now I figure if the AAV ever fails, my wife’s nose would quickly notice :D
 
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Jeff H Young

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aav is not a vent its a check valve. allowing flow in only one direction. when pressure enters aav closes and pressure comes out the p trap (bubbling gurgling) and your p trap is no longer a trap it becomes the vent. So thats the downfall of an aav I suppose an aav cant hurt but in certain senarios they cant help
 

Sokolq55

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So your pump is vented into the room......not outside.,

what a mess.....

This is standard practice in my region. Just asked my sister she has a 3 year old house and hers is plumbed the exact same way. I believe it’s allowed because only grey water that goes through that pump plus the pump inlet itself is always under water so there’s no way for sewer gases to back up. And there’s an additional check valve on the pump outlet.

I don’t know what the code says, but pretty much every basement laundry setup works this way around here. Laundry drains into utility sink, utility sink drains into that pump. Pump is “vented” to the basement ceiling with two inverted 90 elbows at the top with a dryer softener sheet stuck in between for a “filter” lol :D
 

Sokolq55

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Wash water will stink to high heavens if it sits and sours.

Have you ever smelled the stink that can come out of those new front loader washing machines ? Same smell.

I like atmospheric vents on most everything. It solves a lot of problems......forever. But I get it, that’s how it’s done where you live. Understand it’s not correct under most plumbing codes.

Someday when all my other projects are done :cool: I will connect the downstairs shower and that laundry pump to the main stack vent. But only after I completely rewire and cleanup the tangled mess that is the current electric breaker panel lol. So, one day...maybe
 
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