which one does not belong

attached is a pic of basement floor of a triple decker. these are lines running under the basement floor.

we know this much is certain. there are frequent over flows of the bathroom line and we know that the cause can be found at the merge point of the bathroom line an the kitchen line before a single line exits the front of the building. there is too much going on at this point.



the sewage lines are cast iron and old, but the bathroom line is clear of any blockages and looks ok.
condition of kitchen line is unknown

the washer is not permitted, not vented and does not use a slop sink. the usage is really high for this washer. these over flows happen during months where there are many overnight periods with 12 straight hours of usage of this washer at 25 cu ft/hr.

what is the likely cause?
The Washer or
The bathroom line or
The kitchen line

the choices for solution are

remove washer and its high usage

cap the kitchen line from the stack to the washer and create a new kitchen line that meets the bathroom line in the front of the building

cap the bathroom line from the stack to the washer and create a new bathroom line that meets the kitchen line in the front of the building

The cause is a simple, common clogged drain line. Have the lines in question professionally cleaned by a reputable plumber.

we did. the problem still exists

Did you do a camera inspection of the underground piping all the way out of the building from the toilet branch?

yes we did.

what did the camera show ?

looked pretty clear, there was a belly 17' in front of the house, but water was flowing fine at the time of the inspection.

I think that bathroom sewage was getting into the kitchen pipe before the merge of the 2 lines. could the washer cause this to happen. there were times when they were running load after load for 23 hour periods.

a belly will do it.

what happens is, the belly stops the paper and poo from going down the line.

look at like a kid on a slip and slide that hits the pool. you stop.

but the water keeps going, then another flush, some more stops, pretty soon you have a traffic jam of paper an poo

you hit it with a snake and nudge it past the hump, it starts moving again.

nope that is not it.
as i stated: we know this much is certain. we know that the cause can be found at the merge point of the bathroom line and the kitchen line before a single line exits the front of the building. the washer sits very close to this merge point.

we know this because we replaced the kitchen line with a new line from the bottom of the kitchen stack to the front of the building and merges with bathroom line here. the old kitchen line was capped where the washer is.

it worked

i do not believe that the kitchen line was the problem. why would it be.

Well it sounds like you've ruled out a clog or a belly being the problem and the camera revealed no other issues, so one would then think that there is a volume-to-pipe-size conflict. If that is the case, then I don't see how connecting any other branches further downstream would resolve the problem unless there is an increase in pipe size. Sound right?

the washer piping to sewer line was replaced when they capped the kitchen line. they put in a new pvc pipe that is capped at one end and connects to the bathroom line a few feet away and connects to the washer close to where it is capped. i do not know if the pipe size was
increased from what it was before. or if any other changes were made pertaining to the washer connection.
the owner of the washer says that there were no changes to the washer. but he lies.

i bet the pipe size for the new kitchen line was increased. but why would that be necessary. the original pipe size for the kitchen line worked with the bathroom line since the the construction of the building 90 years ago and was approved by the city.

or are you suggesting there may have been a volume-to-pipe-size conflict between the washer and the kitchen line?

could it be that the original kitchen line is smaller than the bathroom line combined with increased volume coming from excessive usage of the washer triggers this volume-to-pipe-size conflict.

if either is true, what would happen

I do believe that there is a correlation between extreme periods of high water usage and the over flows. these over flows were happening alot, each time the date of the over flow was documented, it was during a high usage month based on data from the water company. many of the overflows are not documented.

i appreciate your responses!

What I'm saying is that the overflows are happening at the bathroom and the piping from the bathroom should be no less than 3" and possibly 4", correct. So any pipes continuing down stream would have to be the same size or larger than 3" or 4" and it is assumed that the volume of water from the washing machines is overwhelming the pipes since the possibility of clog or belly affecting the flow has been ruled out. It is then reasonable to surmise that the pipes would still be overwhelmed by volume, still, if a connection is moved further down stream without an increase in size to handle the volume. In summary, if volume-to-pipe-size is the cause then moving a connection downstream would not change anything unless the connection is to a larger pipe size than the bathroom branch connection. Does that sound right?

It still sounds to me like there is a clog/bottleneck/belly causing the problem.

thanks again! i appreciate your patience

it was not a clog or belly. there were no change made to the bathroom line whatsoever and the problem was fixed. this was a chronic problem for years, the lines were being snaked often, and the camera showed no problems except a belly that still exists. then suddenly they stopped after the work was completed.

attached is the new picture.

the old kitchen line (from stack to merge with bathroom line) was probably smaller than the new one (from stack to front of house). but that should not have mattered. a small line can feed a bigger line, no problem, i assume.

Even if the kitchen line had a problem area that often got blocked due to buildup or a crack, and was smaller, it should not affect the line it feeds into. if it gets blocked the flow just will not make it to the line it feeds into. am i correct?

so, as i think you are saying, the move of the kitchen line to merge at a different point should not have mattered?

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I do not know how the washer was connected to the former kitchen line.
i only know how it is now. the underground pbc pipe that connects the washer to the bathroom line is fine. works fine

there had to have been a newer pipe (likely pbc) replacing a section of the original cast iron pipe for the kitchen line, because the washer was originally hooked up many years after the house was built and it had to have a way to get into the cast iron.

it is possible that the previous kitchen line was to small for the washer drain pipe.

on the other hand, it is also possible that while the kitchen line was smaller than the bathroom line it fed into. the section that was replaced and connected the kitchen line to the washer and then to the bathroom line may have been too big to be feeding into the bathroom line.