Drainage question

Ran into an issue with the drain for our washer. We bought our house about 3 yrs. ago from my in-laws (house my wife grew up in). When we were moving them out, I noticed they had a 1/4 turn butterfly type valve on the washer drain line. I was told that the new washers had too much flow for the older lines of the house to keep up with, so they choked it off. I didnt question it and just followed suit, applied the same type of valve and restricted the flow to keep it from overflowing. Needless to say, this year we burnt up the drain pump on our washer, surprise-surprise.
So before I burned up another pump, I decided to investigate what the deal was. I pulled the paneling down from the wall and this is what I found:



The Water softner drain is open ended with the softline from the Kinetico dumping in it and the vent goes out thru the roof. The clean out is a threaded Y-coupling, with the plug directly above the turndown, where the line runs back under the slab to our main drain line.
I tested out an additional vent where the clean out is, with success! All I did was pull the plug out and screw in a threaded male fitting that allowed me to stick a pc. of 2"x4' PVC in and capped it with a AAV. I could run the washer drain valve wide open and force the Kinetico to cycle and drain at the same time and not get a single gurgle or get the drain to even remotely act like it wasnt going to drain.

Before I put an additional hole in the ceiling to properly vent this line, is there anything I should do differently? My plan is to run a 2" section from the original location of the clean out, up into the attic. Then run it over to the original vent and just Y-into it. I'll add a Y-coupling with a threaded inlet for a new cleanout, close to the originals location, in the new vent pipe as well.

I don't know how well your drawing portrays what you actually have, but in installing a proper vent, it must be no more than 60" from the trap, and the pitch of the trap arm in that distance may not exceed 1/4" per foot.

The drawing is not very accurate, the length from the trap to the turn down is @ 36" and only drops about 1/2". The progam I was using would only give me that angle or flat, so I used it.

Assuming your drawing is correct, then the vent is completely useless and the trap is in the wrong location. An AAV will do NOTHING to improve drainage. Install the new vent, and then connect it back to the existing vent riser, AFTER you disconnect the vent from the existing piping.

hj said:

Assuming your drawing is correct, then the vent is completely useless and the trap is in the wrong location. An AAV will do NOTHING to improve drainage. Install the new vent, and then connect it back to the existing vent riser, AFTER you disconnect the vent from the existing piping.

Click to expand...

The AAV was only to see if a vent after the trap would help, I didnt want to leave an uncapped vent sticking up in my utility room in case something happened like a clog or the washer pushing water up and out it. I planned on tying the new vent in to the existing vent this weekend. Also, I have a little extra space to move the trap if need be, whats wrong with its location currently?

It might be more of a matter of your drawing. The trap should be connected directly to the base of the standpipe, and cannot have the "S" bend in it that your drawing shows.

Oh yeah, the trap is directly under the down pipe and doesnt make that extra hump. I'm gonna have to get a real drafting program and make it look correct. Sorry for the confusion and thanks for the help!