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frosty45 · Mar 24, 2009, 09:51 PM

I am remodeling our bathroom and wonder about the need to add a plumbing vent. What is the maximum distance allowed from the vanity drain to the stack without adding a vent?

Thanks

massplumber2008 · Mar 25, 2009, 03:37 AM

Hi Frosty...

Maximum distance will depend on the plumbing code that prevails in your area.

In my area, the maximum distance for vent between stack and sink is 5 feet... ;) (see top drawing). Under most other codes I think it is 3.5 feet maximum.

Anything between 3 and 5 feet would work for me. Anything longer than 5 feet will require you to install an 1.5" vent and run it back to the vent stack... see middle picture below. Notice how the vent pitches back toward the drain and be sure to hang the pipe every 4 feet. The trap wants to end up between 18-20" off finish floor and the vent reconnects into the vent stack at 42-48" off finish floor.

You can also pipe it up as in the alternative piping drawing below... just need to start low on the stack. Again, the trap wants to end up between 18-20" off finish floor and the vent reconnects into the vent stack at 42-48" off finish floor.

Let us know if you have more questions... anytime!

MARK

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speedball1 · Mar 25, 2009, 05:08 AM

Depending on where you live and the code you fall under and the size of your drain.
1 1/2" drain line between 3 1/2' and 5'
2" drain between 5' and 6'.
Note: The newer vanity installations are usually piped with a 2" drain line and reduced down at the trap. Good luck, Tom