ᐅ Is it possible to connect kitchen wastewater to the soil stack?

Hello! I’m new here and just want to jump right in:

Situation: Detached single-family house from 1935, repeatedly renovated by tenants, mostly unprofessionally. The kitchen is to be moved to a different room. Is it allowed to connect the wastewater (sink/dishwasher) to the external soil pipe (down into the basement and from there just below ground level into the soil pipe)? I should mention that there is NO other wastewater discharged on this side of the house. The bathroom, etc., are connected to the sewer system on the opposite side of the house!

I would really appreciate any information!
Good luck, Ally

I assume that by "downpipe" you mean the rainwater drainage system.

In some municipalities, it is allowed to connect both wastewater and rainwater to the same sewer. In others, this is not permitted, and wastewater and rainwater must be disposed of separately. We cannot know what is allowed in your area; you will need to check with your local authorities.

Thank you very much for the information! I have to admit, the situation is already present, but we have a problem: For about a year now, there has been a burrow in the front garden. We initially assumed it was caused by voles, but we were proven wrong—it seems to be rats! Over the weekend, we tried inserting the garden hose into the burrow, and it sounded strange and hollow... the water disappeared immediately. We grabbed a shovel and carefully dug around. About 40 cm (16 inches) below the surface, we found a “pipe” (those ribbed black flexible pipes). Naturally, it was already damaged for a long time, as could be seen by the damp, dirty area around it. At first, we were puzzled, then I brought up the kitchen drainage pipe with the downpipe that we installed (we always thought it was connected elsewhere). And sure enough: it was that. No wonder there are rats there, with food leftovers and dishwasher detergent residues… I don’t want to think about it!

Our neighbor noticed everything and told us that their rainwater pipes lead into drainage pipes and then into the garden and front garden, with a kind of “overflow” into the sewer system! Now we are standing here not knowing what exactly is down there. Given this situation, one wonders whether the plumber did everything properly at the time or if there should have been any concerns raised??? For now, I feel like “the fool.”

Now we are considering: Since 2009, everything has worked (even in this damaged state)! Should we just repair it? But: Where does it lead? For over a year, soil has also been washed into it: is it slowly becoming clogged? Is it actually allowed to use those ribbed black flexible pipes (9 cm (3.5 inches) diameter) for wastewater at all? Is it really a drainage pipe or hopefully a normal sealed pipe?? So many questions.

Unfortunately, I’m not very familiar with this. However, I would say that this hose is probably not suitable for that purpose. It may also not be approved because it is too thin-walled, and possibly for other reasons, but as I said, I’m not sure.

Rats are likely to start using the pipe as a shelter.

Yes, the pipe can also become clogged with soil.

There are pipes with small holes designed to absorb and drain water from the ground, and there are also ones without holes. I can’t tell which type you have there, but it’s probably without holes.

Have a professional come and take a look at the situation.

Personally, I would replace the line with a proper sewage pipe, which would also be installed deeper. Of course, this assumes it’s possible to lay it deeper in your location.

Hello,

AllyMcT schrieb:

Situation: Single-family house, detached, built in 1935, repeatedly "renovated" by tenants, mostly unprofessionally.
The kitchen is to be moved to another room. Is it allowed to connect the wastewater (sink / dishwasher) to the external downpipe (down into the basement and from there just below ground level into the downpipe)?

No, this pipe is reserved exclusively for roof drainage.

AllyMcT schrieb:

I have to add that on the side of the house there is NO other wastewater pipe. Bathroom etc. is connected to the sewer on the other side of the house!

That cannot be the case; you probably just haven’t found another pipe yet. All wastewater has been and is collected inside the house and then discharged below the slab. Whether it then flows into one or two public connections depends on the local authority’s regulations.

To answer your follow-up question: No, it’s not enough to just patch it up. You need to bring in a gas/water installer to replace all wastewater pipes. Better a quick end to the problem than ongoing trouble.

Regards, Bauexperte

Hello! Well, it really is the case that no additional wastewater flows into this "pipe." It only carries wastewater from this one downpipe. And nothing converges under the house either, because before moving in, we had all the wastewater pipes and sewers up to the street replaced by a company (and we were mostly present during the work). A soakaway pit and the old clay pipes were removed and replaced, all on the other side of the house.

When flushing through our "pipe break," I was able to push a garden hose in so far that it must already be outside the property!

Of course, I would prefer a final scare over an endless one, but what concerns me is whether the plumber was allowed to do it this way. The pipe only starts underground about 40cm (16 inches) from where he connected the kitchen wastewater to a standard sewer pipe. So he didn’t see it himself, but he knew all the conditions because he also did the sewer work on the other side of the house during the renovation! And the house is old. As a local, he should also be aware of that. Should he have informed me? Should he have raised any concerns? I’m not a plumber and trusted him to carry out this work.