My Kitchen Sink Has a Drainage Problem

[skeezix]

I have a double kitchen sink. The sink on the right is normal, the sink on the left has a garbage disposal. The disposal drains to the right-hand sink tail pipe via a 90 degree fitting, then the tail pipe goes to a P-trap and from there to a 2-inch drain pipe.

If I fill the right-hand sink it has no problem draining. When I put a stopper in the right-hand sink and let water run until the stopper is covered, the garbage disposal will not drain. That is, I can fill the disposal side several inches and the water will not drain until I pull the right-hand sink stopper. Shown below is a diagram of the sink drains.




The capped pipe used to be a drain for the dishwasher drain. In the drawing the hose marked "FromD/W" goes behind the disposal and connects to the hose that is 4.5 inches below the bottom of the sink.

I have not the foggiest idea how the two drains connect to the clean-out behind the wall. I do know that the clean-out connects to a 2-inch pipe that goes to the main sewer.

 

[havasu]

Do you see a vent stack on the roof above the sink?

 

[Twowaxhack]

Clean all the connecting sink drains with a professional drain cable while running hot water.

 

[FishScreener]

It sounds like the vent line is blocked. You could check by putting the sink in the non-draining mode, and unscrewing the cap on the left trap. Unscrew it slowly, with a catch pan underneath, and see what happens.

 

[Twowaxhack]

It sounds like the vent line is blocked. You could check by putting the sink in the non-draining mode, and unscrewing the cap on the left trap. Unscrew it slowly, with a catch pan underneath, and see what happens.

If what you say is true then how do s traps drain……they don’t have a vent.

 

[FishScreener]

Twowax, if the right hand sink drain is open, it works fine. If you put the plug in, the left hand sink doesn’t drain, until you pull that plug. Then it drains.

The only thing which would connect the two, is vacuum. Thus the problem is a venting issue. And with the strange drain line setup, who knows how thing work in the wall, and where the vent piping is run.

 

[havasu]

Similar to "the finger stopping the water flowing from a straw?"

 

[cliffyk]

Similar to "the finger stopping the water flowing from a straw?"

Bingo...

 

[Twowaxhack]

Similar to "the finger stopping the water flowing from a straw?"

Not at all. There’s no finger over the top of the disposal.

 

[Twowaxhack]

Twowax, if the right hand sink drain is open, it works fine. If you put the plug in, the left hand sink doesn’t drain, until you pull that plug. Then it drains.

The only thing which would connect the two, is vacuum. Thus the problem is a venting issue. And with the strange drain line setup, who knows how thing work in the wall, and where the vent piping is run.

The drain is partially clogged. The vent only protects the ptrap unless that’s the only vent in the building or the only vent before a belly in the pipe.

A kitchen sink will drain fine without a vent.

 

[havasu]

Not at all. There’s no finger over the top of the disposal.

Good point

 

[Zanne]

This may seem like an odd question, but does turning on the disposal make water drain from the left side? I have a garbage disposal in a similar configuration and the stupid thing doesn't always drain unless I turn it on and the vibrations force the water down. I don't have to turn it on for long-- just gets the water flowing.

It does sound like there might be a clog somewhere though.

 

[skeezix]

This 2-story house (living on bottom, bedrooms on top) was built in 1982 and there is a vent pipe above the kitchen sink.

@FishScreener: >>Twowax, if the right hand sink drain is open, it works fine. If you put the plug in, the left hand sink doesn’t drain, until you pull that plug. Then it drains.<<

That's another way of explaining what I have.

I need to try rooting out the drain pipe via the clean-out in the drawing again. The last time I tried it the cable would only go in about a foot and then stop. While I was trying to figure out what was causing that, the War Dept. came in and that was the end of that...

 

[BlueSkyHigh]

While I was trying to figure out what was causing that, the War Dept. came in and that was the end of that...

War Dept.'s can be very scary.

 

[Twowaxhack]

Have a professional clean the drain and it’ll drain with the other stopper in the sink.

 

[skeezix]

>>And with the strange drain line setup, who knows how thing work in the wall, and where the vent piping is run.<<

I don't see what's strange about the drain line setup. Do you mean that it's horizontal? It's always been like that.

The house was built in 1982 and the GD was replaced in 2000 and in 2020. Seems like the problem started a couple years ago. I'll pull the GD drain and check to see if something is clogging it, but I doubt it.

When the stopper in the right-hand sink is open, the GD does seem a tad slow to drain but the water never flows out of the top of the GD and into the left-hand sink. When the stopper is closed, the water level rises from the GD and begins to fill the left-hand sink right at 10 seconds.

 

[Twowaxhack]

Have a professional clean the drain and it’ll drain with the other stopper in the sink.

 

[skeezix]

All very fine suggestions. But...

The problem was the rubber ring around the mouth of the GD was causing the problem. When I duplicated the problem (again for the umpteenth time) and then pushed one of the fingers of the rubber ring down, the water in the LH sink drained away immediately! Thanks to a gentleman named "Reach4" in another forum for his suggestion!

 

[Twowaxhack]

All very fine suggestions. But...

The problem was the rubber ring around the mouth of the GD was causing the problem. When I duplicated the problem (again for the umpteenth time) and then pushed one of the fingers of the rubber ring down, the water in the LH sink drained away immediately! Thanks to a gentleman named "Reach4" in another forum for his suggestion!