Clogged Pipe and Detached Vent Stack, with Photo and Video

Hello all, I recently bought an old home and after about 2 months of no issues, the washer/sink are backing up. I ran a 25 foot auger from the cleanout under the kitchen p-trap and seemed to get some sludge in the auger bit, but it didn’t do much. So, I went in the crawl space to take a video (please watch). A picture is also attached.

What I believe is the biggest problem is the 90 elbow, which I bet is where the clog is. If I put in a long sweep 90 or two 45s and then reattached the vent stack, would this likely fix the issue? I am not sure if the vent stack’s location is an issue due to its position downline after the washer and kitchen sink. There is an AAV on the kitchen sink, but not the washer.

Also, at the start of the video you can see the washer pipe make a sharp turn and then turn from a 2” to a 3” pipe. Is this section up to code?

How bad is this plumbing setup in general?

Thanks for your time, any help is much appreciated.

 

Every few years I go under the house and run my garden hose with an adjustable nozzle so it sprays 360 degrees around the inside of the drain and I feed it through the clean-outs I have located at various places on the line. You'll have to cut in some clean-outs. it's messy but it does a good job of washing out the slime. like you, it is also the drain for my washer and kitchen sink. if that doesn't work then put an AAV on your washer.

 

Along sweep is always much better then an ell or short sweep

You may find it useful to

1- Install a clean out at the base of every stack

2-Every change of directions greater then 45 deg

3- full size clean out up to 4"

 

All the horizontal should have long sweeps. Pipes dont look like they have much fall 1/4' per foot?. the old vent stack isnt needed but the washer and kitchen should have vents didnt see a bathroom ? you could have made that last turn a lot smoother those tight 90s arent good 2 45s or a long sweep and 45 or 22.5 for elelvation change no need at all for that

 

Thank you all for your help! I thought I would tie in the existing vent stack, but is it really not necessary, Jeff? The bathroom is farther down line, right before it exists the house. There is a vent stack on that side.
I'm planning to add an AAV after the washer, which I can use as a clean out as well, correct? Then change the main 90 to a long sweep with a clean out before it. And, finally, tie in the existing vent stack unless it's really unnecessary.