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I have a common drain for three sinks the clogs 1-2x per year. All three sinks back up at the same time and slowly drain. Total distance between sinks is about 25ft. I suspect that the sinks share a common lateral drain pipe and a T comes off that (hidden in walls) to a visible diagonal drain (several bends) and then down. All interior piping. If I snake down a sink, it just goes across to the other sink.

I have cleared the clog by snaking up the diagonal drain pipe (~5ft from a removable coupling). But as stated in other posts, this is probably only creating a hole in the clog. The suspect T is not visibly accessible. The T is probably ~10ft from the closest sink. There's a roof vent somewhere along the lateral pipe.

I have tried running hot water down sinks on both sides of the drain, but that does not seem to help.

I don't want to damage the cast iron pipes or replace them at this time.

Any suggestions for clearing the bigger clog? Anything safe to pour down the sinks that would dissolve hair, scum, etc? I can poor from both sides with or without water in the pipes (~10ft to the T). It will sit there for a while and slowly drain.

best guess of drain configuration

  • pool chlorine will eat hair, but may promote rust. – Jasen Feb 9 at 8:01
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    You could contact a plumber that has a snake with a camera to check the drains. – d.george Feb 9 at 10:14
  • Hello, and welcome to Home Improvement. Nice use of Excel for a diagram! What do you put down the sink? – Daniel Griscom Feb 10 at 0:35
  • Just the typical bathroom sink stuff - water, toothpaste, mouthwash, soap & cleaning materials, unintentional hair, etc. I suspect hair and soap scum are major components of the clog. – excel Feb 10 at 6:35
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Heavy duty professional drain snakes have a variety of attachments available for clearing all kinds of clogs but those are more of a pro tool than DIY.

I would attach one of the inexpensive plastic barbed clog removers to a snake and very carefully run it up the diagonal to the tee.

Cobra Drain Cleaner

You'd want to be very careful to make a good secure attachment so you don't wind up with a remover lost in the drain pipe. I'd probably use bailing wire and electrical tape and at least a 6" overlap. (You'll see you'll want the ring end lashed to the snake - that way the barbs pull the debris back to you.)

With patience there's a good chance the barbed remover will hack up and retrieve the clog.

  • Can you snake down the vent? – Jeff Cates Feb 10 at 21:47
  • yes but it does not help. A plumber tried that. The snake just goes laterally past the drain pipe. – excel Feb 11 at 5:21
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If there's a way to securely plug two of the three sinks, then you might find a toilet plunger in the third sink would help clear the clog. Or, you could use one of those expanding drain cleaner bladders.

  • I may try that. i can remove the sink traps and close two of them as well as the roof vent. One concern: I'm not sure if I can force enough water down the pipe to clear more than a hole in the clog. Once enough flow opens up, the pressure will drop and the water may just go around/through the clog, like it does when I snake from below. Also, if part of the clog is in the lateral pipe, forcing water through may send it to the other side vs. down the drain. – excel Feb 10 at 6:48
  • That's why I was hoping to find a 'pipe safe" solvent I could pour down both sides that might loosen/dissolve the clog. – excel Feb 10 at 6:58
  • See this answer for a possible solution. – Daniel Griscom Feb 10 at 12:39
  • Sounds like a good longer term fix once the clog is opened. – excel Feb 10 at 18:03

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