My kitchen sink clogged all of a sudden tonight. I snaked the drain pipe several times and even ran the hose in the drain pipe in the wall under the sink for several minutes and it drained well. The ptrap is clean. I thought it might be the drain vent so I snaked that too. I came to a point where it stopped but I think that was just a hard turn the snake didn't like. I ran the hose for several minutes down the vent from the roof and it drained well. I figure if water can flow through the vent pipe then air can too. My sink does have a disposal but water flows from the sink to the ptrap. When I plunge the sink water shoots out of the dishwasher vent. The problem looks like water won't go from the ptrap to the drain pipe although everything I checked is open.

So when you plunge you get water out the air gap but the drain and the trap are clear. Is that correct?

You have removed the trap and snaked the horizontal drain in the wall. Is that correct? You also went on the roof and snake the vent down to where the snake hit something and wouldn't go any further. Try this, go back and snake the roof vent again. This time, when you reach the base continue on past the point where the snake hung up. I'll bet you find your clog their. Let me know how you make out. Good luck, Tom

@hkstroud
Thanks for your reply. Yes when I plunge the drain after I let water build up it shoots out the air gap vent connected to the disposal and dishwasher. The first time the drain was clogged it did not even have a slow drain. After I plunged the first time it started to have a very slow drain, but further and more aggressive plunging did not help, except to shoot water all over the place.

It seems like a vapor/vent lock because all the components when tested separately work just not when everything is connected.

@speedball1/Tom
Thanks for your reply. There is a window in front of my sink so I know there are some turns in the vent pipe. When I snake the drain pipe in the wall under the sink I think the vent goes up, drain goes down and connection to the sink is 90 deg to both out of the wall. It looks like a T fitting. When I snaked the vent pipe from the roof it hit something solid like the bottom of 90 deg turn and was hard to get past. I will try harder to get through the bend in the vent pipe. I just figured that if I could run water down there and there was no backup then air could flow too.

Under the house there is one drain for the dishwasher and then the drain for the sink joins and then down to the main line. I know it is somewhere above the main cast iron sewer line because the hose flowed fine for 5 minutes without a backup after I inserted it in the drain pipe under the sink when it was opened up. Maybe water is flowing from the vent pipe on the roof into the dishwasher drain and there is some blockage in the sink drain. Since the sink and dishwasher are next to each other I would think the sink could use the vent from the dishwasher if that vent path is clear.

Yes when I plunge the drain after I let water build up it shoots out the air gap vent connected to the disposal and dishwasher.
Under the house there is one drain for the dishwasher and then the drain for the sink joins and then down to the main line.

Those two statements seem to contradict one another. If the dishwasher drains to the disposal through an AAV vent, how can there be a drain for the sink and a drain for the dishwasher that connect under the floor?

Remove and check the little ell that comes out of the disposal and connects to the drain trap. Sounds like the drain of the disposal (that little ell) is clogged.

Harold,

You got it. I tested the disposal draining water after I took the elbow out and I tested the P trap with out the elbow. It was some beet peels that the disposal didn't chew up and they created a nice little block. Thanks for you help.

Congrats.

Sounds like you have already cleared the horizontal drain line in the wall. Now, take your snake up on the roof and snake the kitchen roof vent. Put out enough snake to reach the base and 15 more feet. That signature clogged. Let me know how you make out. Good luck, Tom