# Plumbing - If a 1.5" 42in long sink trap arm connects into a 2" drain line - How far from the connection does the vent has to be located?

Context: Connecting a 1.5 in diameter 42in long sink + dishwasher trap arm into a 2in diameter drain.

Question:

1. How far, from the trap to drain connection, does the vent on the 2in diameter draine line have to be located? from my research I am getting 5ft but also 8ft from the connection.
2. Can the re-vent of the laundry sink be removed, if the drain is a 2" pipe rather than a 1.5in pipe?
3. How long can the trap arm be if the 2" drain to the vent is 8ft?

• what's horizontal and what's vertical? please provide a sketch with orientation, diameters and lengths Dec 10, 2022 at 0:52
• 8 feet (from the exit of the trap) is the distance if the whole thing was 2" to the trap, because that's the limit where the end of the pipe is still level with the trap weir. Dec 10, 2022 at 1:53
• Thank you P2000. See attached diagram. If the new laundry sink drain is 2in, can I get rid of the re-vent?
– Max
Dec 10, 2022 at 3:03
• Thank you Ecnerwal, this is what I thought. It should be 8ft for a 2in vertical change. But then, how long can the trap arm be, if the exit to the 2in drain pipe is 8ft from the vent?
– Max
Dec 10, 2022 at 3:04
• 8 feet is 8 feet from the exit of a 2" trap in a 2" trap arm. Not from where a long 1.5" trap arm enters a 2" pipe. So the answer to question 3 is 0 inches. Dec 10, 2022 at 14:30