ᐅ Noise Transmission Through Drainage Pipes and Rainwater Downpipes

Dear Forum,

I have the following issue with my small sewage lifting station and my home drainage system. If this is the wrong forum, please feel free to move my post accordingly.

The small sewage lifting station is located in the basement of my detached house (built in 2019). When the lifting station pumps out, I can hear gurgling noises in the bedroom on the top floor. The sound transmission does not occur inside the house but through the main drain pipes and the rainwater downpipe outside. The noises are loud and disturbing. Therefore, I would like to know what I can do about it.

Here is a sketch of the home drainage system:

A drain cleaning company has already conducted a camera inspection of the affected pipes and lines. However, no irregularities (e.g., excessive slope) could be detected. My general contractor said he has never encountered such a case before. Although he confirms that noises of this volume are unusual, he does not know how to solve the problem.

My questions:
- An acquaintance told me that rainwater and wastewater are only allowed to be combined at the inspection chamber. Is this correct? Could this be the cause? As shown in the attached sketch, rainwater and wastewater are already combined in the main drain pipe in my case.
- What other causes could there be for the noise? What measures could be taken to reduce it?

Thanks in advance for any helpful advice.

Best regards
timmy-baut

timmy-baut schrieb:

- A friend of mine said that rainwater and wastewater should only be combined in the inspection chamber. Is this correct?

I can’t comment on the regulations, but it would have been better to have separate piping up to the chamber. Nowadays, separate sewer systems are often installed or existing ones are converted during renovations. In your case, this would mean digging up to the house and installing new pipes. It’s probably not likely right now, but your excavator saved about 300€ by doing it this way (since the pit was already open) and may have caused a major hassle in the future.

My guess is that the gutter isn’t properly isolated from the house. The gurgling sound is then transmitted as structure-borne noise.

WilderSueden schrieb:

I can’t comment on the regulations, but it would have been better to have separate piping all the way to the shaft.

Thank you for your quick response. Would separate piping have been better only in terms of noise reduction, or are there other advantages as well? In the area where I live, there is a combined sewer system, meaning that rainwater and wastewater are discharged together into the sewer anyway.

The main pipe and the wastewater pipe are probably made of PVC. That material does not transmit structure-borne sound. If there is any noise, it must be airborne sound through the downpipe that is open to the rain gutter.

But isn’t it already mentioned in the original post that the sound transmission occurs through the main pipeline and the rainwater pipe?

Couldn’t the problem be solved with a simple backflow valve that dampens the airborne sound?

xMisterDx schrieb:

Couldn’t the problem be solved with a simple backflow valve that dampens airborne sound?

Thanks, good point. If the transmission is indeed through airborne sound, it might work.