Stumped by double vanity

[B. Clark]

Background Info:

• Upstairs double vanity.
• Both sinks won't drain.
• Sink 1 on L side; Sink 2 on R side.
• Sink 2 overflow connects to Sink 1's tailpiece.
• Single-piece vanity top.

Troubleshooting Measures Taken:

• Pulled P-traps and tailpieces.
• Sink 1's tailpiece was full of sediment in overflow tube from Sink 2 (see IMG_4548 and IMG_4550).
• Sink 1's P-trap had some sediment (see IMG_4544) but Sink 2's was clean (and Sink 2 had the clogged overflow tube!).
• Cleaned p-traps.
• Ran 25' Ridgid drain snake in both waste pipes (horizontal to one another).
• Nothing plugging either horizontal waste pipes.
• Took clean-out plug off and ran 25' snake down vertical waste pipe (located just below horizontal waste pipes). No resistance.
• Tried plunging. Nothing.

Meanwhile, when I reassemble both sinks, they still fill up with water.

I am stumped.

All other sinks in the house drain fine (same for showers and tubs).

Thoughts are most welcomed!

Thank you,
B. Clark

 

[James Henry]

Sometimes for various reasons the snake will travel up the vent pipe and not the drain. It takes some experience to notice it, if you put 25 feet of snake down the pipe and it came back clean then you most likely went up the vent.