Practice Guide · Rainwater fee

The rainwater fee — how it is calculated and which applications can reduce it

"We pay every year just because it rains now and then." The rainwater fee (stormwater fee) often only registers when the assessment notice arrives — or when the municipality re-surveys sealed surfaces by aerial imagery. This guide explains how the fee arises and which routes exist to reduce it — each of them an application your municipality decides on.

Author: Alvaro Burgos Cifuentes, M.Sc.Last updated: September 2026

At a glance

  • With the split wastewater fee, you pay separately for foul water (based on drinking-water consumption) and rainwater (based on the connected sealed area in m²).
  • In NRW the rainwater fee in 2022 ranged, depending on the municipality, from 0.15 to €2.19/m²/yr (LANUV 2022) — a population-weighted mean of €1.13/m², median €0.83/m². Your specific rate is set in your municipal fee statute.
  • The fee can be reduced via the connected area: disconnection/infiltration, green roof, retention — each on application and per statute.
  • None of these reductions happens automatically or is guaranteed. They are applications with supporting evidence; the authority decides.
  • For single-family homes it is usually a two- to low three-figure amount per year; for commercial sites with large roof and yard areas, recurring four- to five-figure sums.

1. How the rainwater fee is calculated

Many municipalities charge the wastewater fee on a split basis: the foul-water share follows drinking-water consumption, the rainwater share follows the sealed area connected to the sewer, in square metres. The key word is connected — that is the lever any reduction works on.

The rate is set by your municipal fee statute. In NRW the rainwater fee in 2022 ranged from 0.15 to €2.19/m² per year; the population-weighted state mean was €1.13/m², the median — the typical case — €0.83/m² (LANUV, Wastewater Disposal Status Report 2022). Your local statute is always decisive.

A worked example for illustration: 150 m² of connected area works out — depending on the municipal rate — to roughly between €25 (€0.15/m²) and €330 (€2.19/m²) per year; at the state mean of €1.13/m², around €170. And that year after year. For commercial areas with large roofs and yards this quickly adds up to four- or five-figure amounts.

2. The lever: the connected area — on application

The fee follows the connected sealed area. Surfaces whose rainwater no longer runs into the sewer can be assessed differently. The usual routes — whether and by how much is set by your municipal statute, and the authority decides on the application:

Routes to a reduction — each on application

  1. 1Disconnection & infiltration: surfaces demonstrably infiltrating on the property are in many places no longer assessed. This often requires an infiltration verification — and possibly a water-rights permit. Whoever fully disposes of their own rainwater can also be exempted from the transfer obligation (§ 49 (4) LWG NRW); the fee consequence is governed by the statute.
  2. 2Green roof: assessed in many statutes with a reduced factor.
  3. 3Retention with throttled discharge: likewise reduced depending on the statute.
  4. 4Correcting the area survey: aerial surveys sometimes include areas that are not connected at all — the self-declaration is the place to correct that.

3. What is worth it, and when

For a single-family home it is usually a two- to low three-figure amount per year. Whether a structural measure pays off for that is an honest calculation — and sometimes the answer is: no. That is exactly what we will tell you.

For commercial sites with thousands of square metres of roof and yard, disconnection is by contrast one of the few cost blocks that can be reduced permanently and recurringly. Here the assessment sensibly begins with a water audit that brings together areas, notices and savings potential.

4. What we do — and what we do not

We deliver the part where applications fail: the reviewable document — an infiltration verification per DWA-A 138-1, an area assessment, and on request support through the procedure. You file the application; your municipality decides on it.

We plan and sign off under professional responsibility — the construction (disconnection, swale, soakaway trench, green roof) is carried out by your firm, your landscaper or your builder. Responsibility for the design stays with us, execution with your trades.

Whether the effort is worth it for your property, we tell you beforehand — even if the answer is "no".

Sources & legal basis

  • LANUV NRW — Wastewater Disposal Status Report 2022, Ch. 10 "Cost-covering water prices" — rainwater fee: population-weighted mean €1.13/m² (Tab. 10.2), median €0.83/m², range 0.15–€2.19/m² (as of 2022)
  • DWA-A 138-1 — Infiltration systems for stormwater (October 2024)
  • § 44 LWG NRW — Disposal of rainwater (re § 55 (2) WHG)
  • § 49 (4) LWG NRW — Exemption from the transfer obligation where the owner disposes of the rainwater themselves
  • § 55 (2) WHG — Local disposal of rainwater
  • Your municipal fee statute — decisive for rate, factors and application routes — varies by locality

Sources last checked on 5 September 2026.

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Is disconnection worth it for your property?

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