There is a similar thread on this topic. I've got a new LG WT1101CW top load washer and our drain pipe can't keep up with the flowrate coming from the washer. It's a great idea to add a larger diameter tube to the drain pipe to allow the excess water time to drain away.

Is there any significance to the second 2" pipe at the outlet side of the trap? Or is this just another drain pipe coming from "upstairs"?

Proposed solution from the other question

  • No photo? 2nd pipe? Connecting to a new washer with old drains what is the problem? – Ed Beal Apr 6 at 21:06
  • 1
    I can't imagine that your washer is overwhelming a 1-1/2" pipe. Its own drain is probably 3/4" at best. That's less than a quarter the size. What is the actual problem? – isherwood Apr 7 at 15:37
  • New washers after overwhelm old 1.5 pipes. The big pipe in your picture serves as a reservoir for the volume of water pumping out. the smaller pipe is likely an air admittance valve for a less than optimal venting option. – Kris Apr 7 at 21:40

Is there any significance to the second 2" pipe at the outlet side of the trap?

No. The vertical pipe downstream of the trap is either another drain coming in from above or a vent stack. It isn't involved with the capability of the 3" section to provide some surge capacity for the draining washer.

(Well, I suppose it does add a little bit of capacity, insofar as water can fill that drain/vent pipe up to the level of the opening at the top of the 3" section. So that's a little bit of surge capacity. But it isn't its primary purpose.)

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.