Waste water backup.

[FatDaddy]

I have an odd situation and will do my best to explain with thanks in advance for any advice given.
A brief explanation to the photo:
The riser has a clothes washer discharge in it and is 18" above the assembly leading to the 4" cast iron line that
leads to a drywell outside.
The line leading to the left goes to a slop sink about ten feet away.
The 2" pvc drains the kitchen sinks.

My issue is that for a long time I have seen signs in the sink of a small backup. It seemed to occur when the washer was discharging. Last night it almost filled the sink with really nasty black wasterwater and the sink did not drain at all. When I inserted a garden hose in the riser, water backed up into the sink.
I vacuumed the water out and called my septic guy.
He and I put fifty+ gallons of water into the slop sink and it drained strongly. Without a cleanout cap on the 4" he could not use a big snake and he could not send a snake down the riser due to the bend. He went in via the pvc.
It SEEMS as though the water backs up when the washer is discharging and additional water from either upstairs or the slop sink is entering the system. My guess is that the 4" line to the drywell is as clear as any seventy year old line can be.

Any thoughts about my predicament? I am $200 poorer and nothing has changed. I will reconfigure the piping to include a cleanout cap but wonder if the current configuration is the problem.

 

[Reach4]

That horizontal wye connected to the laundry sink is going the wrong way... However that is not causing the sink to not drain at all; that has to be a clog. But after the clog is removed, the washer still might blow water at the sink if the wye is still facing the wrong way.

I think there is a problem with the standpipe venting too, but the venting is not causing the backflow to the sink. I think that elbow should be a longer sweep, but that is not causing this problem.

I think your cure will involve adding a big cleanout to the 4 inch and redoing other stuff.

I am not a plumber.

 

[Sponsor]

 

[FatDaddy]

That horizontal wye connected to the laundry sink is going the wrong way... However that is not causing the sink to not drain at all; that has to be a clog. But after the clog is removed, the washer still might blow water at the sink if the wye is still facing the wrong way.

I think there is a problem with the standpipe venting too, but the venting is not causing the backflow to the sink. I think that elbow should be a longer sweep, but that is not causing this problem.

I think your cure will involve adding a big cleanout to the 4 inch and redoing other stuff.

I am not a plumber.

Thanks. I sort of agree. It must be in the configuration leading up to the 4" connection.

 

[Reach4]

Thanks. I sort of agree. It must be in the configuration leading up to the 4" connection.

I think the blockage is on the septic tank side of your picture.

 

[Orangewood]

The drywell could be past its useful life.

 

[FatDaddy]

I think the blockage is on the septic tank side of your picture.

I was leaning towards that BUT the lines seems clear...again, as clear as a seventy year old line can be. It must be something to do with the jumble of connections and while I want to correct the issue, as long as I watch the drainage and do not stress it with too many discharges at once I may be able to buy time.

 

[FatDaddy]

The drywell could be past its useful life.

No doubt, BUT with the amount of water we sent down the drain without issue, I have to think it is the piping that leads to the four inch.

 

[FatDaddy]

I think the blockage is on the septic tank side of your picture.

That was my immediate thought,thus the call to my septic guy. Not so sure now. Re-piping is in order but they configured it that way for a reason(s) as the previous owner probably used experienced plumbers.It is on my "to-do" list but not high (it is a long list) and as long as I watch my discharge and do not do too many things at once I may be OK. Thanks.

 

[Reach4]

I was leaning towards that BUT the lines seems clear...again, as clear as a seventy year old line can be.

How did you access that line to determine it was clear? Did you run a thin 25 ft snake into the standpipe, or what?

I have to think it is the piping that leads to the four inch.

There is what -- 8 inches of common pipe between ( the junction of the laundry sink and the standpipe output) and the 4 inch pipe?

 

[Reach4]

as the previous owner probably used experienced plumbers.

I really really really doubt that.

 

[FatDaddy]

I really really really doubt that.

Doubt what?

The "wye" is about 3 1/2" o/c from the start of the 4" line. The riser with the p-trap is about 13 1/2" o/c from the 4" line.
The septic guy said that since he could not fit a big headed snake into the line there probably was little good done by his snaking
with the small snake. He went out, if I had to guess thirty+ feet.

 

[Reach4]

Doubt what?

I doubted the thing I quoted: "the previous owner probably used experienced plumbers."

I was presuming that the wye and the standpipe and the line from the slop sink was installed by plumbers for the previous owner. It may have been done by the previous owners themselves. Maybe I was too subtle. So here is not subtle: I am not a plumber, but IMO whoever it was was either not competent as a plumber or worse.

Your septic line could not be rodded because the person who added the sink drain and the standpipe got rid of the cleanout.

Based on your reported symptom, we know there is a path between the standpipe and the sink. We know that the water is not making it out to the septic. That tells me that the problem is between the junction between the standpipe path and the sink path. The blockage could be in your picture downstream of that, but the blockage seems more likely to be past the wall.