Dirt and rainwater connection - Is the offer fair?

Hello,

we have just received the first offer for a dirt and rainwater connection.
Attached is a picture of the property with the house and the planned pipes marked.
We have received (from the general contractor) an offer of €6500.
Originally, €3000 was planned in the construction cost estimate for this.

Does anyone have any idea why the offer is €3500 more expensive than originally assumed?
And is the price reasonable? It seems too expensive to me; I have now requested comparison offers from local civil engineering companies.

Originally, 3000€ were planned for this in the initial construction cost calculation.
Does anyone have an idea why the offer is 3500€ more expensive than originally assumed?

Which services or conditions were calculated in the original calculation and what does the current offer look like? You just need to compare the positions. We don't know either one here.

Which services or conditions were calculated in the original estimate and what does the current offer look like? You just need to compare the items. We don’t know either one or the other here.

Nothing more specific was named in the original estimate. It only stated:
Wastewater sewer (approx. 10 m) with inspection chamber 1500€
Rainwater disposal (approx. 25 m) connection without soakaway chamber 1500€

The subsequently submitted offer includes 33.15 running meters for wastewater, 64.35 running meters for rainwater.
I don’t know how they arrived at these values, if these refer to meters. Where should 64 meters of rainwater pipe run? Our property isn’t that large. Or does "LFM" not mean "running meter"? Unfortunately, I am a total layman when it comes to such topics. :/
Services in the offer:

Wastewater sewer DN 125 including all fittings made of KG pipe, supply and installation, depth up to 0.80 m, including connection to the existing shaft (max. depth of existing shaft up to 1.50 m). Note: The lengths and depths specified here may vary on site. A separate billing will then take place.

Rainwater sewer DN 100 including all fittings made of KG pipe, supply and installation, depth up to 0.80 m, including connection to the existing shaft (max. depth of existing shaft up to 1.50 m). Note: The lengths and depths specified here may vary on site. A separate billing will then take place.

In the original calculation, nothing more specific was stated. It only said: Wastewater sewer (approx. 10 m) with inspection chamber €1500 Rainwater disposal (approx. 25 m) connection without infiltration chamber €1500 The newly submitted offer states 33.15 LFM for wastewater, 64.35 LFM for rainwater. I don't know how they arrive at these values, if they mean meters here. Where should 64 meters of rainwater pipe run? Our property isn’t that big. Or does "LFM" not mean "linear meter"? Unfortunately, I am a total layperson when it comes to such topics. :/ Services in the offer: Wastewater sewer DN 125 including all fittings made of KG pipe, delivery and installation, depth up to 0.80 m, including connection to the existing chamber (max. depth of existing chamber up to 1.50 m). Note: The lengths and depths given here may vary on site. Separate billing will then take place. Rainwater sewer DN 100 including all fittings made of KG pipe, delivery and installation, depth up to 0.80 m, including connection to the existing chamber (max. depth of existing chamber up to 1.50 m). Note: The lengths and depths given here may vary on site. Separate billing will then take place.

Originally 35 meters, now it’s 100 meters! It’s okay to deviate, but measuring three times as much is amateurish! Who specified the 35 meters? I would ask the general contractor directly how the deviation came about. That way, they know from the start that you are checking!

Hi

You just need to measure the lengths of the pipes on your site plan.
Don't forget the vertical lengths for the rainwater as well.
Roughly estimated, I come up with dimensions between the first and second offer.

Olli

Nothing more specific was mentioned in the original calculation. It only said:
Wastewater channel (approx. 10 m) with inspection shaft 1500€
Rainwater disposal (approx. 25 m) connection without infiltration shaft 1500€

Those were probably standard flat rates without concrete planning.

The subsequently submitted offer includes 33.15 linear meters for wastewater, 64.35 linear meters for rainwater.

If the lengths match, the offer is also correct. Keep in mind that the straight path is not taken. If your house is 10x10 m, you already have 30 m of pipe horizontally without even adding another meter to the street.