We are building our own nest - the way & report into the house

I think this is incorrect information. The decisive factor should be

Zweckverband Abwassergruppe Dübener Heide, Bad Düben Landkreis Nordsachsen

"Wastewater and Fee Statute" dated 19.4.2012, page 11

§ 25 Fee standard for stormwater disposal (1) The wastewater fee for the partial service of stormwater disposal is measured according to the amount of stormwater that accumulates on the property connected to the public wastewater facilities and is discharged into the public wastewater facilities. Properties that are dedicated to public traffic in accordance with § 2 SächsStrG are exempt from the wastewater fee for the partial service of stormwater disposal.

The standard for the wastewater fee for the partial service of stormwater disposal is the sealed property area and the type of sealing. The sealed property areas of a property (§ 26 para. 1) are multiplied by a factor which is set taking into account the degree of water permeability and evaporation for the individual types of sealing (§ 26 para. 2). ...

§ 26
... If in an individual case it can be proven that not all the stormwater is discharged into the public wastewater system in a permissible manner from the area underlying the fee assessment (paragraphs 1 and 2), the wastewater fee is to be appropriately reduced upon written application by the property owner, the hereditary building right holder, or the otherwise legally entitled person for structural use in the individual case. Sealed property areas that are drained into the public wastewater system wholly or partially, permanently or temporarily, are to be taken into account. § 24 para. 4 applies accordingly.

The property is probably within their area of jurisdiction, right?

Oh yes, it is located there, I spoke with them....

How do I then calculate this fee?

I was just told that wastewater costs nothing to discharge because the wastewater meter runs with the water meter. Therefore, discharging will cost nothing since we do not draw any "fresh water".

Why don’t you draw any fresh water? Wastewater is of course billed based on the meter of the normal drinking water...meaning 100m³ of water consumed = 100m³ of wastewater...exceptions only apply when an extra garden meter is installed...

Discharged rainwater is calculated based on the roof area here...then some kind of annual rain average is calculated which is multiplied by the roof area...but I can’t say exactly because we also do not discharge but let it infiltrate.

Oh yes, it's there, I spoke with them.... How do I calculate this fee then?

For us, it also depends on the sealed area x fee (which I don't know right now). Asking helps. The annoying thing is mainly that you practically pay for the weather, over which you probably have no control.

With us, it also depends on sealed surface x fee (which I don't know now). Asking helps. The annoying thing about it is mainly that you practically pay for the weather, which you probably have no influence on.

Okay, I understand, would building a cistern be a countermeasure?

In a cistern, water does not infiltrate; you can only "store" it and then use it yourself. You would need infiltration or a cistern and infiltration in the overflow. Sometimes superficial infiltration is also allowed.

Here we require a water law permit from the lower water authority. This permit is only granted if you calculate exactly how much rainwater to expect and how efficient the infiltration (or similar) is. You should therefore consult experts on the topic, because otherwise, you might be told a lot of nonsense. A local geologist should be able to help you.

Water does not seep away in a cistern; you can only "store" it there and then use it yourself.
You would need infiltration or a cistern and infiltration at the overflow. Sometimes surface infiltration is also allowed.

In our area, you need a water law permit from the lower water authority. You only get this permit if you precisely calculate how much rainwater to expect and how capable the infiltration (or similar) is.
So you should consult experts on this topic, otherwise you will be told a lot of nonsense. A local geologist should be able to help you.

Thanks for the info... This is really all a hassle... A lot of patience is required, I am currently working through the list of additional costs and gathering the information.

What is still open, is there an overview of where to get all this information?

Building permit....................................634 €

Installer water meter/construction water......257 €

Provision interest KfW124...................8 €

Association of private builders......................90 €

House surveying.....................................584 €

Provision interest KfW124...............124 €

Approx. 100 m³ topsoil disposal...........1800 €

Expert building inspection...............370 €

Construction water, advance payment................390 €

Rental of band dryer, 2 weeks...................230 €

Rainwater and sewage shaft... .3000 €

Civil engineer, connections.............................510 €

Supplementary permit, garage...............90 €

Rainwater drain and courtyard gravel ..3300 €

Garage, HT pipes rainwater...............65 €

Courtyard gravel, house edging......... from 3000 € (without surface material)

Laying terrace...................................from 2000 € (without surface material)