How many kW pump sewage lifting system single-family house

Hello everyone,

We need your help again:

Our house is located on a slope where there is no direct sewage pipe nearby. Our neighbor, of course, had the same problem and installed a lifting station (a shaft with a pump in the driveway). We need the same now to connect to the existing line.

We have now received 2 offers, one for a 2.2 kW pump and one for a 4 kW pump.

I don’t know if anyone can help us theoretically here without having seen it on-site, but I have the following data: Our wastewater flows into the shaft that we place in our driveway. From there, the mentioned pump pumps over a distance of 120 meters and has to overcome 0 meters in height until then. There the connection to the existing line is made. From there, the wastewater has to cover 175 meters and 16 meters in height.

Since one of the pumps has almost twice as much kW and accordingly costs twice as much, we would be grateful if someone could give us a tip or if someone by chance has the same scenario at home.

Thanks in advance.

Dimensioning is also a question of quantity. How is one supposed to give a tip there?

Dimensioning is also a question of quantity. How is one supposed to give a tip there?

Can one state a quantity there? It is a single-family house with 5 people (currently 3)

Well, there is a lot to say about that, because besides the number of people in the house, there are areas where surface water should also go into the sewer. This is relevant for the sizing. It is important to prevent backflow from the sewer. If the pump does not have to pump the wastewater against sewer pressure and no very high throughput due to surface water is required, then the smaller pump will certainly be sufficient.

Well, a lot can be said about that, because besides the number of persons in the house, there are areas where even the surface water is supposed to go into the sewer. That is relevant for the sizing.
It's important to prevent backflow from the sewer. If the pump does not have to pump the wastewater against sewer pressure and no very high flow rate due to surface water is required, then the smaller pump will certainly be sufficient.

Thanks already for your help...

So the surface water does not go into the sewer, only the wastewater that flows through the drain. The pipe from the pump to the sewer has a diameter of 32mm, so this total 300-meter-long pipe simply flows into the sewer. Is there any way to calculate if the performance is sufficient for the height difference and length the wastewater has to overcome?