ᐅ Are backwater valves always necessary in flood-prone areas?

wrobel schrieb:
If drains are located below the backflow level, a lifting system is mandatory.

As far as I have been told, this is not necessary. If the backwater valve is closed, no wastewater should be discharged below that level. As long as there is still a toilet above the backflow level, a lifting system is not required; an electric backwater valve is sufficient.

toxicmolotow schrieb:
And as shown in the last diagram, this is not allowed. In my opinion (as a layperson), the barrier must be between the drain in the basement (KG) and the incoming pipes from above.

//EDIT: There is actually no backwater valve installed in that setup, so it functions as shown. However, pipes are needed that first go upwards and then downwards.

Alternatively, with a backwater valve: Separate wastewater pipes must lead to the sewer—one for below the backflow level and one for above it. This ensures continuous drainage above the backflow level and inflow below.

Exactly what Uwe is saying is what I mean.

The company Kessel has created a clear diagram for this.

I see exactly that problem in the diagram, because the pipe continues upward right at the washing machine connection.

wrobel schrieb:


If drains are located below the backwater level, a sewage lifting station is mandatory.


Olli

Hello,

I’m quoting myself again. This is what really matters.

In this regard, Toxi is not entirely wrong; it would definitely be better to connect the drain lines from the ground floor and upper floor separately and independently of the basement to the inspection chamber. In case of a blockage or backflow between the house and the chamber, both lines can then operate independently.

If you take another close look at the first sketch, you can see that the water from the basement is pumped above the backwater level (the pipe bend visible on the ground floor). If you imagine filling the chamber with water, you’ll notice that water first flows out of the top of the chamber before it can run back into the basement through the bend.

Only this way—and no other—is the installation professionally correct.

Olli

That's right, the picture at the top shows a small sewage lifting unit installed. In this case, it would also be acceptable without a backwater valve.

wrobel schrieb:
I’m quoting myself again.
That’s what really counts.

Then, in this housing development, almost every building would be non-compliant. Because every basement has an electric backwater valve, but none has a lift station.

What just occurred to me that we also need to consider: Wrobel is, of course, correct in this case—if the sewer invert level is above the drains, so the wastewater can’t flow by gravity, then a lift station is necessary. But as long as gravity drainage is ensured and the other conditions (toilets, etc.) are met, a backwater valve is sufficient.

Ok, for me, this means that, as planned, I do not need backflow valves since I have no outlet below the backwater level. Very good... Thank you all.