Lifting system backflow plate

Hello everyone,

we are just about to submit the building application and our developer claims that we are obliged to plan and implement a backflow prevention system.

As far as we understand, this is clear. What we really cannot understand, however, is why we are not allowed to install a backwater valve for sewage and are allegedly required to install a lifting system.

The situation is as follows:
The plot is completely flat, rainwater is not allowed to be discharged into the sewer system throughout the entire development area but must drain via an infiltration pit. Our ground floor is about 30 cm below the last backwater level in the sewer. The plot/development area is located on top of a hill, so water does not come down from any hill but rather drains quickly.

This means that, in case of an event that might occur every 5 years and the sewer system can no longer handle the rainwater, we are supposed to install a pumping station.

For us, this is clearly a matter for a backwater valve and not a pumping station. This system serves a different purpose for us. Furthermore, this system is not allowed to be built outside the building, so we are supposed to get a flap and a system under the floor slab in the house connection room.

The whole thing is supposed to cost about 7000 euros even without earthworks.

Are we thinking too simply or is the construction company right?

By the way, for the insurance a backflow protection is important. A flap would therefore be sufficient and would certainly achieve the same effect.

Thank you for your opinions

I think you are confusing something. The pumping station is for wastewater, not rainwater. The rainwater should be discharged on the property.

The pumping station lifts the wastewater so that it can get from your lower house to the higher street. But since the street is only 30cm higher, the difference in height should actually still be enough. Otherwise, please write more precisely what you want.

The rainwater pipes are NOT connected to the street network if infiltrated on site; a pumping station makes no sense unless the house is significantly lower than the rest of the property. But even then, it would probably be cheaper to simply dig deeper for infiltration.

What about a basement? If you have one, and there is wastewater present there, then the lifting station is exactly intended for this.

Especially when the house is 30 cm below street level, the drain pipes are at least another 30 cm deeper, so it is quite possible that everything will back up on you.

It is solely about the case that the channel would not be able to handle excessive rain. Only if that should be the case will the system activate. The house is on flat land slightly above street level, which is adjusted by paving or by a step to the front door. The last backwater level in the channel (a whole piece down the street) is about 30 below our ground floor. Neither the street nor the house have been built yet. However, the plan data is now available in this form.

We build without a basement