ᐅ House Drainage to Sewer Manhole – Lowering the Backwater Level?

Hello everyone,

We have a situation where we need to connect our house drainage to a sewer shaft located on a slope. Due to the incline, the manhole cover is about 1 meter (3 feet) above the basement floor level of our house.

Is it conceivable to build some kind of overflow in the sewer shaft towards the slope, which would effectively lower the backwater level?

The proposed overflow is shown in the sketch on the right. Protection against animals, etc., is of course accounted for.

The entire drainage system and the shaft are completely on our property.

Lowering the shaft would be difficult because of the slope. Raising the house is not an option. The basement contains the bathroom and living spaces.

I could also imagine branching the "overflow" off from my house drainage pipe.

Could something like this work, and would it be permissible?

At least to me, this currently seems like the only option to avoid a lifting station (proper solution) or a backwater valve (technically not quite correct).

Thanks and best regards

Frank