Dishwasher fixes Sink.

Factual Questions
1

What happened:

Step 1. Sink gets stopped up.
Step 2. I try to fix it using Draino, but it fails.
Step 3. I try with a plunger, again fails.
Step 4. Plumber comes in, I pay him $35 and say I tried a Draino and a Plunger, he turns on my Dishwasher, (which was next to to my sink) and sink clears up and starts draining.

I am not mad at the Plumber, it was $1 to turn on the dishwasher, $34 for knowing/learning the trick.

But I would like to know WHY turning on the dishwasher worked.

2

Your dishwasher is almost always in close proximity to your sink. . .they share the same drain (most of the time). A couple of guesses:

  1. The dishwasher forces a LOT of water down the drain, thereby dislodging the clog. Also, the dishwasher water is most likely very hot, which probably helps loosen greaseballs and such. This might not work every time, but perhaps the plumber got lucky.
  2. Maybe if the clog is above the dishwasher drain connection in the sink drain, the suction from the rapidly draining water below the clog would help to loosen and pull the clog through?

However, if the clog is too far down and too stubborn, I could see a scenario where turning on the dishwasher would only cause a LOT of water to be regurgitated up through the sink.

I’m sure there’s a plumber around the board somewhere, I’m just a novice homeowner handyman type (which means my knowledge or lack thereof can be dangerous :slight_smile: )

3

Did anyone else see this thread title and think: “Rock breaks Scissors?”

4

I’m going along with the “very hot soapy water” guess. Things to consider:

Dishwashers almost always join the drain above the garbage disposal. Practically all clogs occur at or under the garbage disposal, negating the “suction form underneith” theory.

Dishwasher water is “pumped” out of the dishwasher, which means that it could provide more pressure when draining than the gravity force on the water leaving the faucet, but I don’t think that that happens due to the air gap. (BTW, the fact that the water is pumped out means “if it isn’t working, you just shut off the dishwasher before you get a LOT of water regurgitated up from the sink”.)

That said, Draino sucks, and Plungers are pretty useless on clogs on the other side of a garbage disposal, and it’s not all that hard to remove the elbow joint yourself and clean it out, in my personal experience.

-lv

5

I thought “And the waiter and line cook cleaned the bathtub”
Another possibility is the clog was really an air pocket at the joint of the dishwasher drain and the garbage disposal. Turning on the dishwasher activated the impeller on the pump and collapsed the pocket.

6

In Mass. air gaps on dishwashers have not ben required for a long time and therefore are very uncommon. It could vary state to state but I would guess that most states do not require an air gap so the water would be entering the drain under pressure.

Put me down for hot water under pressure theory. Another thing to consider is sometimes the dishwasher gets water that is hotter than what comes out of your faucet, so it could be really hot water under pressure.