Redoing bathroom. Have a galvanized vent line thatís corroded.

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Old 01-24-21, 08:30 AM
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Redoing bathroom. Have a galvanized vent line thatís corroded.

The down pipe above the sink trap is corroded behind it about half way down and actually broken off. Should I just cut it and cap it at the other down pipe, or should I cut it out and and join it with rubber couplings and PVC? If rubber coupling, where should I cut and join?



 
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Old 01-24-21, 09:07 AM
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I would absolutely, 100% replace the tee downward with PVC. Galvanized drain pipe is definitely beyond it's life expectancy and is either rotting through at this point, or so gunked up that it will cause slow drains forever.

Whether you replace the vent portion is really up to you. If the roof is just above, I would probably replace it.

If you do decide to keep the galvanized vent, make sure you support it well before you cut it. It's pretty heavy and will drop down once cut. Also, once it's all re-connected, check the boot on the roof as it may need some extra roofing cement or some fixing since the pipe may move a bit and you don't want to get an unexpected leak.
 
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Old 01-24-21, 09:14 AM
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The tee down? The only tee I see is at the sink drain. Can you draw on the pic where I should cut and replace?

Iím three floors below the roof. Had boot replaced last year. The stack is about five feet to the left, but donít have access to it without an incredible amount of demolition.
 
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Old 01-24-21, 02:06 PM
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I don't know. I read your description three times and I'm still confused.

The pipe above the tee is strictly the vent. Where the red arrow is shows tremendous down pressure based on the weight of the galvanized pipe. You would have to support the pipe at that point to keep it from coming down the wall.

Where is the break..... where the blue arrow is ?
 
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Old 01-24-21, 02:24 PM
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I would use metal plumbers tape (the metal tape with the holes in it) to support it where I drew red. Make sure it's well-supported.

Then I'd cut it at either of the green marks. I'd probably choose the horizontal cut, as long as the pipe is solid enough, but either way works.

Use a shielded no-hub coupling to transition to PVC from there down.

 
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Old 01-24-21, 03:24 PM
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Yellow arrow. In the back below the round birthmark on front is where the crack is. Goes about halfway down the pipe. You can actually see itís dislodged from the elbow.
 

Last edited by Lurker99; 01-24-21 at 04:01 PM.
  #7  
Old 01-25-21, 01:27 PM
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The galvanized makes another 90 about three feet up on the right side where it connects into the stack. Am I keeping the galvanized vent and patching it with PVC, or am I adding a PVC vent that'll be inside the vanity? If anybody is confused, the crack is right where PJMax drew the yellow line, but in the back. The top of that pipe is dislodged/corroded from the elbow also.
 
 

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