Took out a double sink and installed a single basin, single drain farmhouse sink. The old stainless steel double sink drained just fine, no issues at all, no gurgling, no slow draining, all was fine. Put in the new single basin, single drain, farmhouse sink and it is EXTREMELY slow to drain. I slowly unscrewed one of the P trap connections and while water leaked out, the water in the sink rushed out and down the drain once air was introduced. Because this started after putting in the farmhouse sink, right away, my question is what's the difference in plumbing a farmhouse sink in vs a double basin double drain sink? I did snake out the drain all the way to the main drain (only about 8 feet to the main drain so that was pretty easy), I also ran water down my vent pipe, no issues. But sink still does not drain properly. The sink bottom is above the height of the drain also. Any tips would be appreciated.

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For giggles, I just did another snake, 50' this time. The end of the snake was visible through the outside cleanout towards the septic. With that, I know if there was clog, it's gone now. But (there's always a but)............still doesn't drain. I loosened the P trap again to let a little air in (yes, it leaked) and it drained right out. Went up on the roof, ran the snake down the vent pipe to the sink, no clogs. Still won't drain.
Any suggestions?

How about a picture of the drain under the sink?

Old piping depending on material can corrode from the inside out making the ID smaller than it should be
An air admittance valve under the sink may help or a repipe to the stack/ main drain

Put in an air admittance valve late last night. The draining actually got slower. Put about 4" of water in the sink last night around 9 pm. This morning at 5 am there was about 1/4" still in it..............

Just added photos to the main post. Thank you sir.

With the AAV in place, it's still slow? Does it drain good if you loosen the AAV to let air in?

What size snake did you use?

Yes. I put that AAV in that you see in the photo last night around 9 pm. It actually made the sink drain slower. I used a 50' snake that went all the way down and through the main drain and was visible outside in the main cleanout towards the septic tank. Pulled the snake through and back in probably 40-50 times while spinning with a cordless drill. Zero difference at all.

What I mean is, if you loosen the AAV does it drain much better? You said you loosened the previous P-trap and it let some air in and drained better, so will loosening the AAV make it drain better as a test?

Your snake may not have cleared the blockage. A pencil size snake may have only poked a hole through a greasy slimy kitchen blockage, and once it passes through it continues on snaking downstream. When you pulled the snake back the grease ball just got shifted and reformed the blockage 8 inches further. You may need a bigger head.

Every thing seems to be piped correctly
Like sum said you may need a thicker cable I would normally use a 5/8” cable with a drop head auger on the end for a 1 1/2” kitchen drain especially if it’s pvc all the way to the stack

By not using the kitchen drain for a couple days/weeks the sludge/grease may have dried up causing a stubborn clog

Ahh, sorry, I misunderstood. Yes, when I loosen the AAV, air comes blowing out and then the water comes leaking but the sink does drain down faster.

The cable I used was one on a reel that you can hook up to a cordless drill. Pretty small.

Try the following harmless 'can't hurt, may help' technique. Will cost pennies + an hour of your time (mostly waiting).

Dissolve as much baking soda as you can in 2 quarts of warm (not hot) water.

Have two cups of white (or other) vinegar waiting and ready to pour.

Pour the baking soda solution down the drain.

Count to ten.

Pour the vinegar down the drain.

Wait 15 minutes and snake the drain again if necessary WITH WATER RUNNING down the drain.


If still stopped up you will need a pro with proper equipment.


ps. remove the AAV but keep the fitting as a c/o

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"Measure Twice & Cut Once" - Retired U.A. Local 1 & 638

DEFINITELY going to try that! Thank you!

1. unscrewing the AAV should also allow drainage.
2. YOU PROBABLY HAVE SOME sort of obstruction in the "main line" creating a double trap