Channel Shaft Backflow - Backflow Valve?

Hello dear house building forum,

So far, I have always avoided creating a post. But with my question, I simply want to explicitly describe the situation on-site.

We have extended our detached house and are already quite far along (currently plastering is being done). A new bathroom was planned and built in the extension. The wastewater from the bathroom flows into our combined sewer (there is only combined water in our village). Behind the bathroom wastewater, rainwater is also discharged, and then it goes directly to the sewer shaft at the street. My architect tells me that I need a double backwater valve between the bathroom and the rainwater at the KG pipe. However, my bathroom is ABOVE the backwater level at the street, so I always read that it is not necessary to install a backwater valve, especially since if one is required, an electrical one would be prescribed, which would of course be somewhat more costly.

I basically have no problem installing a backwater valve... but if, apart from a blockage in my KG pipe, it makes no sense, I do not see the necessity.

A brief description of the location:

O (sewer shaft) Shaft cover is still 35 cm below the bathroom's finished floor level
|
|
|
|
________L (rainwater inlet)
.................|
.................| (Here my architect would install a double backwater valve)
.................L (bathroom)

I hope my question is precise enough.

Regards, the builder.

Hello again.
Doesn't anyone have an opinion or any advice for me?

Does no one have an opinion

I could imagine that your eighties computer graphics, I would say, "don’t exactly immediately make sense to the majority."

I can imagine that your eighties-style computer graphics, so to speak, "do not exactly spontaneously make sense to the majority."

Hello, okay I can understand that, I deliberately did not upload a drawing or even the sewage plan because I hardly see posts here with drawings etc. (which are still normally answered). I had assumed that the mention of the backwater level BELOW bathroom height is already sufficient. But no problem, I can gladly present it better. Maybe an image via Paint is also not good, but I would rather not use the official KG plan. I hope this way my question can be better understood.

Hi

Since the backflow level is below the bathroom drains, I see no need for a backflow valve here. To avoid backflow in case of a clog and also to have an additional inspection and cleaning opening, I would provide a small shaft in front of the bathroom.

Olli

Morning

Since the backflow level is below the bathroom drains, I don't see any need for a backflow valve here.
To avoid backflow in the event of a blockage and also to have an additional inspection and cleaning opening, I would provide a small shaft in front of the bathroom.

Olli

Hi Wrobel, thanks for your answer. That's also the only thing I've been able to find so far in my research. I have to say that my architect was generally not exactly a lucky find for us, so I wanted to turn to the forum with this topic.

The inspection and cleaning opening sounds good, what would be suitable there? If I Google it now, I find, for example, DN110 pipes with DN400 shafts? A silly question, are these closed odor-tight? Does anyone have experience with this? Because that would be near our terrace.