Kitchen sinks won't drain after renovation

[az350x]

Greetings-
We've recently moved in to our new (to us) home in rural Oregon, which we are finishing up renovating. The house is a 1998 manufactured home. Before we demoed the kitchen earlier this year, we used the kitchen sinks for dishes, etc. with no problems. As a manufactured home, the kitchen sinks are plumbed with 1 1/2" drain lines, and most fixtures are vented under the counters/vanity tops, including the kitchen.

We replaced the kitchen cabinetry, counters, sink, dishwasher (new one not yet installed), faucet, and added a new disposal (the house has never had one). We hired a local plumber who redid the plumbing under the sink. The drains are outside of the wall (behind cabinets), and drain pipe runs through floor, for what it's worth.

I'm not thrilled at all with all of these interior vents (as opposed to through-the-roof), but it seems to be an accepted practice and there's not much I can do about it at this point-especially the kitchen.

So the issue we're having is the sinks seem to "lock up" and not drain. One drains slowly, both will hardly drain at all. Also, when you drain one, it will back up into the other. This happens IMMEDIATELY when you pull a plug, as opposed to shortly after draining begins like it would if the line were obstructed somewhere downstream.

I have a drill-mounted Ridgid "snake," which I used today and ran it several feet down the drain pipe under the sink (after disassembling the drain setup under sink). The snake ran freely as far as I could, came out clean, and you could hear it banging around in an obviously-empty pipe as far as I ran it. I'm positive the drain line is free of obstructions.

On a hunch, I removed the new Studor Redi-Vent that the plumber installed when he piped the kitchen. I carefully ran water in one sink, and it drained 100 times better than it has to date. The other sink (with disposal) also drained perfectly with the vent removed. I swapped the Redi-vent for an Oatey (new) that I had, and the problem returned. I was hoping the first vent was defective, but it happens with either.

At this point, I'm confident that there's some issue with the plumbing layout or something. I THINK that the previous drain pipe setup (long-since disposed of) did not have a slightly-graded cross piece from the sinks to the vertical drain line down through the floor, which the new setup does. Instead, I believe there was more of a downward 45* sloping line. Could the added velocity of the water then have served to help the vent pull open and do its job, as opposed to the gentle grade that the new setup employs? Again, with no vents installed (have to be careful though because it will back up/overflow out vent stack under counter if I push too much water through it, as I learned the hard way today!

So, I'm stumped. I have a call in to the plumber. I suspect there's something wrong with the mechanics of the newly-installed drain line, as two brand-new under-counter vents both behave the same, and no vent installed let's it drain like crazy.

Can a y be installed and a second vent be added at same height to increase air intake?

I could probably post a photo if needed, but not sure how to do it on this forum- do I need to host it elsewhere?

Thanks for any feedback.

 

[az350x]

So I figured out the picture posting.

 

[Sponsor]

 

[Terry]

With AAV's, you need at least one open air vent through the roof. They can't all be AAV's.

 

[Plumber69]

Really it should still drain. You may have negative slope below the floor. Or there's a ptrap installed below the floor to. Two ptraps on the same drain would cause this

 

[az350x]

With AAV's, you need at least one open air vent through the roof. They can't all be AAV's.

There are two through-the-roof vents on the house, but they are toward the rear of the house nearer to the bathrooms.

If it matters at all, the home is about 1,700 sf, with 1.75 baths.

 

[az350x]

Really it should still drain. You may have negative slope below the floor. Or there's a ptrap installed below the floor to. Two ptraps on the same drain would cause this

The setup that was removed was the same, with p-trap under the sink, and it worked fine before. The only thing I can think of is, IF I'm remembering correctly, the lower cross pipe in the pic I posted, while having obvious grade, may be different than before. I think I remember that feed to the vertical, through the floor pipe having a much more aggressive angle, like possibly 45 or so.

If that were the case, do you think the added velocity of draining water from the added angle would do a better job of "pulling" the AAV's (not sure what that means, but I'm presuming it's the undersink vents I have) open and drawing air?

I can't think of anything else it could be, as I almost positive that's the only possible difference...

 

[Plumber69]

Post a pic of a side view of your drain. Where it tee's up to the aav

 

[Plumber69]

Right where the pipe goes down through the cabinet. Where does it go. There has to be negative slope somewhere. When you drain your sink it's pushing air probly keeping your aav closed. You need somewhere for the pushed air to go freely.

 

[az350x]

Post a pic of a side view of your drain. Where it tee's up to the aav

Does this view help?

 

[Reach4]

I think plumber69 suspects a belly in the pipe in the crawl space.

I think it would be interesting in a case like this to have the air pressure go to a tube dipped into a glass jar filled with water. That would form what is called an open air manometer. It would be a cheap way to measure pressure/vacuum without needing calibration. Whether that tube connection would temporarily replace the AAV, or whether the tube would tee off on the way to the AAV, it could be a useful diagnostic IMO.

 

[Stuff]

Someone needs look underneath the house. Take a level. Maybe the pipe going through the floor wasn't secured and got pushed down when the changes were made.

 

[az350x]

UPDATE- the plumber came by today and had a look. He saw why I suspected a vent issue, and couldn't see any reason why we would HAVE a vent issue. He ended up fixing the problem- a clog in the line under the house, about 30' down the drain line, before the kitchen drain line merged with any of the other fixtures in the house (they're all at the other end, and meet in the middle of the house where they head to septic tank).

He used a pressure washer and some sort of "jetter," which unplugged whatever (grease, likely) was plugging the line. He put it all the way back together and it works AWESOME.

I guess I'll stick to flying airplanes for a living and leave the hard stuff to the experts...

Thanks for all the replies, all!

 

[Stuff]

Good to hear things are fixed. Always better when when you have a pro on site.

 

[hj]

Your problem was NOT that you did not have enough air, it was that you could not get the air in the pipe out, and that is something NO "Studor" vent can do. Once he removed the obstruction, the air could exit down the sewer line and the sinks drain properly.