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New Laundry Tub - Venting Needed?

Posted by tom_in_seattle (My Page) on
Sat, Nov 27, 10 at 20:25

I'm installing a large Kohler drop-in cast iron laundry tub in the main floor laundry toom and would like to know if this needs to be vented as I was under the impression that if you drain into a larger diameter pipe no extra vent is required.

The drain on the tub is 1-1/2" and that will go into a 2" 90-deg in the wall, run about 2 feet horizontial, then turn 90 and go down through the wall into the crawl space. The 2" line connects with the 3" waste/vent line for the upstairs master bath shower and WC.

This 3" line also carries waste from the main floor clothes washer. Without opening up the laundry room wall I don't know how the washer vents. It may have a vent that goes up and connects with the vent line for the master bath shower directly above.

If I need to add a vent, can I just go up vertically xx feet, then over to the assumed washer vent, which I'd guess would be about 4-5 feet horizontally away.

Thanks for any help. I'm under the UPC.


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RE: New Laundry Tub - Venting Needed?

I believe the distance allowed between a plumbing fixture trap and the vertical vent piping depends on the diameter of the drain line not what you stated which is if you drain into a larger diamter pipe no vent is needed. That being said, I think in your case, since you have 1.5 inch on the laundry tub, the trap arm(pipe between the trap weir and the vent pipe) should not be longer than 3.5 feet(42 inches)before it reached the vent line.

Double check with your city plumbing inspector and pose the question to him/her


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