Are backwater valves always necessary in flood-prone areas?

If the processes are below the backwater level, a lifting station is mandatory.

As far as I have been told, it is not necessary. If the backwater flap is closed, wastewater should simply not be discharged below. As long as there is still a toilet above the backwater level, a lifting station is not required, an electric backwater flap is sufficient.

And the way it is shown in the last graphic, it is not allowed to operate like that. The barrier must, in my opinion (layman), be between the drain in the basement and the pipes coming from above.

//EDIT: There is no backwater flap installed there, so it works like that. However, you need pipes that first go upwards and then downwards.

Alternatively with backwater flap: Separate wastewater pipes must lead to the sewer once for below the backwater level and once for above the backwater level. This ensures that above is constantly drained and below flows in.

Exactly what Uwe says is what I mean.

The company Kessel has made a nice graphic for this.

I see exactly the problem in the graphic because the line continues upwards directly at the washing machine connection.

If the processes are below the backwater level, a lifting system is absolutely necessary.


Olli

Good morning

I quote myself once again.
That is what really counts.

Toxi is not entirely wrong in this regard, that it would clearly be better to connect the lines from the ground floor and upper floor separately and independently from the basement to the inspection shaft.
In case of a blockage / backwater between the house and the shaft, both lines can then be operated independently.

If you take another close look at the first sketch, you can see that the water from the basement is pumped over the backwater level. (the pipe bend visible on the ground floor)
If you now imagine filling the shaft with water, you can see that water first escapes over the top of the shaft before it runs back into the basement via the bend.

Only this way and no other is the installation professional.


Olli

Right, in the picture at the very top there is a small lifting system installed. So it would also be okay there without a backflow preventer.

I am quoting myself again. That is what really counts.

Then this would not be standard-compliant for everyone in the construction area. Because in the basement everyone has an electric backflow flap, but no one has a lifting system.

What just occurred to me, which we of course also have to consider: Wrobel is of course right in this case if the sewer invert is above the drains, so it cannot drain by gravity. Then a lifting system is necessary. But as long as that is ensured, and the other conditions (toilets, etc.) are met, a backflow flap is sufficient.

Ok, for me that means that, as planned, I do not need any backwater valves since I do not have an outlet below the backwater level. Very good.... Thank you.