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pinkertonpv 06-04-2010 09:14 AM

Laundry room remodel
I have moved my laundry room to my walk out basement. How important is it to have a vent pipe for the washing machine drain. The basement drain connects to part of the original drain right where the drain enters the ground in the crawl space. I had to remove a portion of the old drain to make the connection which makes the basement drain not vented. Do I have a pbm? The old vent connected in the exterior wall of the ldry rm just after the p trap. I can reconnect the new portion of the basement drain to the old drain thus reconnecting the vent to the new drain, but the vent pipe will be 6 or 7 feet from the basement p trap. Will that be a pbm?

Alan 06-04-2010 10:05 AM

Yes, you need a vent.

Yes, you can connect old drain to old vent, and connect new vent to old drain. Make sure you have the proper configuration of vent before your p-trap. :thumbup:

pinkertonpv 06-04-2010 11:35 PM

1 Attachment(s)
I have attached a line diagram of the two drain lines and the vent line. Not real clear but the vent will be 6 or 7 ft downstream from the p trap. Will it work OK? Reduce the size of the diagram if necessary and rotate till you get proper alignment.

Alan 06-05-2010 01:24 AM


Your vent has to be vertical at least 6" above the flood level rim.

The way you were describing it, it sounded like it would be ok, but given the diagram above, that is not legal.

just a guy 06-05-2010 07:23 AM

depends where you are located and what codes are observed as to it's legality, in philadelphia it would be legal and work with no problem.
we are allowed 12' branch from vented line for single fixture

pinkertonpv 06-05-2010 08:30 AM

ldry room vent
Thanks for commenting. I want to do what's right, but mainly I want it to work correctly. The vent pipe will not be any different from the original washer drain system. Still where it originally was and extending thru the roof. the end result when I reattach the pvc I cut to add the new drain will be that the vent pipe will be 6-7 feet behind the p trap for the new washer. Distance of fall will be the same. My concern now is will that 6-7 ft between the p trap and the vent pipe opening be a pbm. I am thinking from you guys comments that this will work OK, just may not be up to code. Is that right?

pinkertonpv 06-05-2010 10:16 AM

Laundry room remodel
I have tested the drain several times and the water flows freely. P trap appears to work fine. Next is to reattach vent. :)

Alan 06-05-2010 12:38 PM


Originally Posted by just a guy (Post 451446)
depends where you are located and what codes are observed as to it's legality, in philadelphia it would be legal and work with no problem.
we are allowed 12' branch from vented line for single fixture

I doubt with the vent going horizontally right off the drain. :huh:

Alan 06-05-2010 12:40 PM

I seriously doubt with the way you have drawn it, that it's going to work right at all. With the vent horizontal so low, you're going to have suds and water backing up into the vent. The vent can't work properly if it's full of water, and it's only a matter of time before the vent clogs completely with soap scum, dirt, and lint.

pinkertonpv 06-05-2010 01:28 PM

laundry room remodel
1 Attachment(s)
Alan, my dwg was a pretty bad in depicting the precise configuration of the vent vs drain. The vent is never horizontal. The vent drops 3 feet from the ptrap to where it connects to the PVC going underground and out of the crawl space. A Portion of the old W/M drain is now used as the vent. There is not much chance of water backing up into the vent unless there is a clog in the lines. I have drawn another diagram showing floor joists, crawl space, ground and pipe to better clarify. Do you think this will work OK?

I do appreciate your help and apologize for causing confusion. I have reconnected the old drain line now used as a vent.

Alan 06-05-2010 01:49 PM

That still would not fly here, but you should consult your local code to be sure.

The vent should come off the top of the trap arm, meaning that the p-trap should not be above the vent opening by more than one pipe diameter.

I'm not saying it will or won't work, but it looks like you'll end up with a siphoning problem there.

pinkertonpv 06-05-2010 03:12 PM

ldry room vent
Alan; I understand. What you are saying is besides the code, the configuration I have may siphon the water from the p trap and allow gases back into the house? If that occurs I may add an air admittance valve just behind the p-trap if i can find one small enough to fit. Appreciate you advice and info.

fpeftw 06-05-2010 11:30 PM

1 Attachment(s)
try this
Attachment 21313

Alan 06-06-2010 12:04 AM


Originally Posted by fpeftw (Post 451849)

That isn't legal either as far as I know. :huh:

fpeftw 06-06-2010 01:15 AM

ok, why?

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