Are backwater valves always necessary in flood-prone areas?

Since we are building in a flood-prone area, in my opinion it can still happen that water pushes through the sewer system. What do you think? Do I still need backflow valves then?

What do you prefer? That the sludge comes through the door in case of a flood, or that it bubbles up from the basin? That's a rhetorical question.

When discharging rainwater, in my opinion it makes sense to install one between the on-site drain and the rainwater discharge point, so that the sludge is not forced into the building if the pipe is clogged or because the pipe can’t handle it.

But I’m not an expert... Maybe call the AZV?!

Hello again

yes exactly like that and only like that is correct. as shown in the sketch.

In the processes on the ground floor, all are above the backflow level.
In the basement, drainage is done above the backflow level using the lifting system.
In the picture, on the pipe coming from the pump that is led over the bend on the ground floor into the wastewater pipe in the basement.

Olli

It is completely irrelevant whether it is a mixed system or not. If processes are below the backflow level, a lifting system is absolutely necessary. Olli

And just as it is shown in the last graphic, it must not work that way. In my opinion (layman), the blockage must be between the drain in the basement and the pipes coming from above.

Otherwise, the bathwater from the upper floor will flow back out of the drain below when the sewer is closed.

We have a backwater valve for the wastewater connections in the basement (washing machine, heating, floor drain shaft, utility sink). This was explained to us as follows: It is designed to prevent water from the sewer from pushing into the basement. Up to the height of the lowest window, this is a must, since the insurance companies (almost always) only cover flood damage. This refers to water coming through the windows etc. Water coming through the wastewater pipes is backwater and usually not insured. With a backwater valve, it is insured if the maintenance and test protocol is completed. In a true flood, one certainly has other worries ... Backwater can always happen quickly and through no fault of your own.

I don't really understand it now, though....

says that the sketch is correct says that it must not work like that....

Actually, I thought it should fit like that.... And whether a backflow valve is necessary here or not, I haven't been able to find out so far. As a layperson, you basically assume that the nice people who plan the house know what to do. However, I'm just not so sure...