Air pressure in sink drain pipe prevents drainage

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Iceman 64

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Hello - I am an American living in Sweden and am trying to fix an issue under our sink where the drain water can not drain unless I pull out the light gray flexible tubing inserted into the dark gray piece (pictures below) to allow some air vent, otherwise the air pressure in the pipe does not allow any drainage at all.

The upper piece is only inserted into the bottom piece, it is not fastened. The thinner flexible piece on the right is the dishwater drain tube.

When a large volume of water is dumped into the sink, like when emptying a bucket for example, the system seems to get overwhelmed and the water cannot drain fast enough, the upper pipe gets forced deeper into the lower pipe closing off the air, then water overflows out of gap an runs all over. The force of a lot of water creates a back pressure that the pipes cannot vent.

It has been happening more often now, with less quantities of water to trigger it.And now happens when the dishwasher is run. The water still drains fine when just the tap is running. If I forced the two pipes together, then there is no drainage at all.

I snaked the line today as far as I could, about 40 feet, and forced through some sludge, but it didn't seem like any major blockage.

The two pipes are not connect fast, but only one inserted into the other. I have been using a workaround where the top pipe is not inserted fully into the bottom piece to allow some venting. But that is now failing.

It is a fairly new kitchen install (within the past 5years) and I asked a local plumber when it first happened if perhaps there is a venting issue, but he said it was not venting, snaked it real good, but said that was about all he could do.

In summary, if I push the two pipes together, there is no air venting and no drainage. As a workaround, I pull the tubes apart slightly to allow some venting which enables drainage. But this can lead to leakage, and the system gets overwhelmed when, for example, I pour a bucket of water in the sink or fill then empty the basin, and water leaks out an onto the floor.

Drainage in our shower and all other sinks in the house are fine. So I am thinking there is something wrong with the set up versus an issue with the main sewage line running out of the house.
Looking for some advice......Thanks!
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JG plumbing

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I don't quite know Wendy to tell you to do becuse I don't know Wendy will fit there in Sweden. I think i would do what Bill eluded to. Take that flex pipe that is coming out of the top of the trap and loop it up high and drape it straight back done into the floor. The excess flex that is zig zagging needs to be a high loop.
 

Twowaxhack

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It could be what Bill alluded to but I’m thinking the drain is obstructed in some way.

So it worked for 5 yrs ?
 

Iceman 64

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It could be what Bill alluded to but I’m thinking the drain is obstructed in some way.

So it worked for 5 yrs ?
It only worked for the past 5 years due to my workaround of artificially venting the pipe by pulling it out slightly.....
 

Twowaxhack

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It only worked for the past 5 years due to my workaround of artificially venting the pipe by pulling it out slightly.....
So it’s never worked correctly since the remodel 5 yrs ago ? Did it the drain work fine before the remodel ?

What was done during the remodel ?
 

Iceman 64

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So it’s never worked correctly since the remodel 5 yrs ago ? Did it the drain work fine before the remodel ?

What was done during the remodel ?
I would say it never really worked correctly since. The kitchen was totally blown out, gutted, and re-done. Totally new plumbing and everything. Upon discovering the problem, I called the plumber and he did not comment on the configuration. He only snaked the line a few times. We just refrained from pouring large quantities of water in the sink and letting a basin-full of water drain slowly.

The drain worked fine before the re-model with the old plumbing as far as I could tell. If there were any hidden leaks, I was not aware.

I dont think there is another P-trap under the floor, but the line makes a left turn then runs under the cabinet space where it connects to a larger drain pipe before turning into the floor.(photo).
 

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JG plumbing

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I dont see a second P-trap in the floor, only an elbow where the sink drain line connects into the larger floor pipe
The ptrap's vent is all wadded up like I said and bill said. You have water in your vent.
 
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Iceman 64

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That looks like a dishwasher drain hose to me, which granted does need a high loop. I'd be surprised if that was a vent.
Correct. This was the dishwasher drain hose, which I looped up high, but it did not resolve the problem. When I push the upper drain hose tight into the lower fitting, the sink backs up. No drainage. When I pull it out slightly, there is a sharp air sucking sound of air and the drain pipe clears.

I think I have some venting issues somewhere. Wondering if the issue is related to air vent that vents up through the roof. But all other fixtures in the house do not have this problem. This is a strange case, it seems to be isolated to this line only.

I saw online where someone installed an air admittance valve in the under-the-sink drain stack, to correct for defective roof vents or ones that are not up to code, Seems like a simple solution, but not sure how exotic or common it is. (or if the device is available in Sweden)

Got a plumber coming next week Wednesday, but trying to do my investigation to sanity check his prognosis.

Back in the US I had a good plumber, wish I could fly that guy over here....
 

JG plumbing

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OK. If that's your dishwasher drain then I don't know what your have going on there. I assumed it was acting as a vent for that thing they are calling a trap.
 

Iceman 64

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OK. If that's your dishwasher drain then I don't know what your have going on there. I assumed it was acting as a vent for that thing they are calling a trap.
Thanks anyway for the advice, though. Gave me a good start. They have some kooky set-ups over here...
 

Twowaxhack

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You probably have a partial clog, almost completely clogged. So the drain is acting like it’s being drained into a sealed container.

It was probably working like a combination waste and vent until it clogged up.

I think you have obstructed drain pipe at some point in the system.

You need to cable the drain while you have some hot water flowing down the pipe to wash as you clean with the cable.

good luck 👍
 

Iceman 64

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I called a specialized drain cleaning service and the guy came out the next day. There was a clog in the line at the basement level. He busted it out with a vinyl hose cable powered by a motor in his truck. He had a whole mobile set-up in his truck, the whole job took about 15 minutes. If I would have tried it myself, it would have taken a half a day.

Thanks for the advice everyone, we're back in business!
 

Twowaxhack

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I called a specialized drain cleaning service and the guy came out the next day. There was a clog in the line at the basement level. He busted it out with a vinyl hose cable powered by a motor in his truck. He had a whole mobile set-up in his truck, the whole job took about 15 minutes. If I would have tried it myself, it would have taken a half a day.

Thanks for the advice everyone, we're back in business!
I wish you would’ve took pics ! Glad it’s working.
 

Twowaxhack

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I think i would do what Bill eluded to.
Since you like to tell people to look definitions up.......please learn the difference between allude and elude.

You’ve done this several times. There’s a difference you know. 😘

Bills not running from anyone is he 🤡

Maybe the EPA ? How about The FBI for price fixing on toilet repair ? 🤡

I was really hoping the “ dishwasher vent hose “ was the problem. I wanted to be wrong once.......
 
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