Before I moved into my house two years ago, I had to replace my lateral sewer line which was replaced with trench-less technology by a reputable local company.

I was very happy with their work (which got inspected and passed) but just recently I suddenly became very nervous when I realized that the kitchen sink (and dishwasher) does not seem to connect to any sewer line in the house. Now I am very afraid they may have made a mistake and all my kitchen sewer just runs into the soil under the concrete pavement outside of the house. How realistic is this?

Let me explain with a schematic and picture:

enter image description here

The sewer line runs outside of the house as indicated in the schematic. The sewer line was replaced in the light grey part using the hole indicated in the dotted blue box (shown in the picture when they did the work). From the left is a sewer line coming from an outbuilding. From the bottom comes the sewer line from the house (bathroom and laundry). The replaced line runs towards the right to the road.

Now there is a kitchen with dishwasher as well, indicated with the three red question marks. From the basement I can very clearly see that there is no other pipe entering the sewer from the bathroom. I also clearly see the bathroom sewer line exiting the building through the basement wall, straight to where the wye in the picture is.

Under the kitchen, I do see the vent stack from the kitchen sink in the cripple walls. No further pipe is visible (and in particular, no visible connection in the hole they dug out, see picture). Hence I think there is no other way than that this kitchen sewer must connect to the main sewer line with another wye. But the hole indicated in the picture was the only hole they dug. They did not open the concrete pavement at the location where the kitchen is located.

Is it plausible that the kitchen sewer WAS connected to the old sewer line outside with a wye but they missed it and ran the trenchless replacement through the old wye? And now the wastewater is all going into the earth, right next to the new sewer line?

Or it it possible at all that they could connect it somehow to the new line without digging another hold for it?

Do I have any feasible DIY way to figure this out?

  • What sort of trenchless technology did they use? My impression is that a "missed branch" in a typical trenchless install would usually end up plugged, not open, and you'd find out very quickly when it backed up. Mar 16 at 21:21
  • Not sure what you mean by “which technology” but I have more pics if needed. First they pulled a metal rope through and then they pushed a loong PVC(?) / flexible pipe from the hole in the picture all the way to the street. Is there a test I could do? For example, it doesn’t back up if I run the water for, say 10min. Would it back up when it wouldn’t be connected to the sewer?
    – divB
    Mar 17 at 3:05
  • Could you explicate the part about seeing the "vent stack" under the kitchen? Vents would all be at the level of or above the traps at the kitchen fixtures.
    – kreemoweet
    Apr 14 at 6:43

2 Answers 2


Under the kitchen, I do see the vent stack from the kitchen sink in the cripple walls. No further pipe is visible

There are 3 possibilities:

  1. Kitchen drains out the side of the foundation where you can't see it.
  2. Kitchen drains laterally in the wall where you can't see it.
  3. Kitchen drain is not connected, and food waste is falling into the basement.

Part of the confusion might be that the drain and the vent are in two different locations.

Even in the first case, the kitchen drain would have to be connected to the old sewer line or the new sewer line. Where it goes after that isn't a major concern unless the pipes are backing up somewhere. I wouldn't worry just based on a visual check of the basement pipes.


Alright. I opened the cleanoup, put my ears in and sequentially ran water from the bathroom and kitchen sections. I could hear the former but not the latter.

Based on this, I contacted the company which did the trench-less sewer replacement two years ago. They came in a very happy mood. As soon as I showed him the crawlspace he got quiet and startled. I think he immediately realized that indeed, a wye was forgotten.

Today they are here correcting the work for free under warranty (hopefully and hopefully no further unforeseen issues happen). Need to cut the concrete again and as an additional issue, there is a heat pump now exactly above it, they they needed to cut the concrete in front of the heat pump and then dig in sideways underneath.

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