New Rainwater Management Regulations for Developers in the Czech Republic
Rainwater management should be addressed at the design stage because rainfall is expected to be retained and infiltrated on the property where local conditions allow it. An unsuitable solution can delay permitting or final approval and may cause damage to neighbouring property. This article explains when a hydrogeological assessment is needed, how to choose a suitable drainage solution and what to check before construction begins.
Key takeaways
Legal Basis and the Obligation to Retain Water in the Landscape
The key legal framework is Act No. 254/2001 Coll., on Waters, which establishes the obligation to ensure the infiltration or retention of rainwater. This requirement is further detailed in regulations related to the new Building Act and in the decree on construction requirements.
The state administration recognizes that the effective management of rainwater directly on a property is one of the most efficient tools for climate change adaptation. Therefore, this obligation is being enforced with increasing strictness.
The obligation applies not only to new constructions but also to modifications of existing buildings, such as extensions or structural alterations that change drainage conditions. If you are applying for a building permit, you must also address rainwater management.
Hierarchy of Solutions According to the Law
The law does not allow for an arbitrary choice of solution. Instead, it defines a binding hierarchy of procedures that developers must respect. You cannot choose an administratively simpler option if a technically feasible, higher-priority option is available.
Preference of Procedures from Infiltration to Drainage
According to Section 5(3) of the Water Act and the decree on construction requirements, the order is as follows:
1. Rainwater infiltration on the property
The first and preferred solution is to let rainwater infiltrate directly on the developer's property. This solution is the most desirable because it supports the natural water cycle and is implemented using infiltration systems.
For infiltration to be considered fulfilled, the land must be geologically suitable and large enough. The new decree on construction requirements no longer works with fixed percentages but refers to standard values and land-use planning documentation.
2. Retention and discharge into a separate storm sewer
If infiltration on your property is demonstrably not possible, the second option is retention and regulated discharge into a watercourse. This is usually done via a storm sewer that does not lead to a treatment plant.
3. Regulated discharge into a combined sewer system
Only if infiltration is not possible and a separate storm sewer does not exist in the locality does the law permit the regulated discharge of rainwater into a combined sewer system. The emphasis is on the word "regulated," which means the water must be retained on the property and discharged gradually.
Hydrogeological Survey as an Essential Document
A common mistake that the lawyers at ARROWS law firm encounter is the absence or poor quality of a hydrogeological survey. Without it, it is impossible to legally design a method for rainwater disposal.
What a Hydrogeological Survey Is and Why It Is Important
A hydrogeological survey is conducted by a person with professional competence. Its purpose is to determine the infiltration capacity of the soil and the groundwater level. The survey serves as a crucial legal and technical basis for the project documentation.
The survey typically includes:
drilling exploratory boreholes on the property,
an on-site infiltration test,
a risk assessment (impact on neighboring properties, wells, subsoil stability).
The cost of a quality hydrogeological survey for a family home is in the range of several hundred to a thousand EUR. It is an investment that prevents serious errors in the project.
How This Document Is Used in Practice
The hydrogeological report is attached to the application for a building permit. The official at the building authority uses it to assess whether the proposed solution corresponds to the actual conditions on the property. If the report is missing or flawed, the authority will suspend the proceedings or reject the application.
The legal team at ARROWS law firm recommends obtaining the survey as early as the feasibility study phase, so the project designer knows what size retention tank or infiltration system to plan for.
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Systems and Equipment for Rainwater Management
The choice of technical solution must comply with standard ČSN 75 9010 (Infiltration Systems for Rainwater).
Types of Equipment
Surface infiltration systems: Swales, trenches, infiltration basins. They require more space but are easier to maintain and have an aesthetic appeal.
Underground infiltration systems: Infiltration blocks and tunnels. They save surface space but require thorough pre-filtration to prevent clogging.
Retention tanks with water reuse: Underground tanks where water is accumulated for further use.
Sizing is Key
The size of the infiltration system is calculated based on:
the size of the drained area (roof, paved surfaces),
the infiltration coefficient (from the hydrogeological report),
design rainfall intensities (based on the frequency and duration of rain).
Undersizing an infiltration system is a frequent cause of disputes. If the system overflows during heavy rain and floods a neighbor's property, the property owner is liable.
Legal Risks and Penalties
Underestimating the issue of rainwater carries both public law risks in the form of state fines and private law risks, which include disputes with neighbors.
Fines for Illegal Discharge into the Sewer System
If you discharge rainwater into a combined sewer system without a permit and a contract, it is considered an unauthorized discharge.
Fine amount: According to the Act on Water Supply and Sewerage Systems, the fine for a natural person can be up to CZK 100,000. For legal entities and entrepreneurs, the penalties are in the hundreds of thousands to millions of crowns.
Detection: Municipalities and sewer operators use so-called smoke tests. Harmless smoke is forced into the sewer, and if it emerges from your gutters, the illegal connection is proven.
Denial of Final Approval or Permit
The building authority may not issue a final building approval or occupancy permit if the implementation of rainwater management does not correspond to the approved project. This can block the use of the property or the drawing of a mortgage loan.
Neighbor Disputes and Damages
Under the Civil Code, you must not disturb your neighbor to an extent unreasonable for the local conditions by directing water onto their property. If your poorly designed infiltration system causes waterlogging of a neighbor's house or erosion of their garden, you are liable for the damage caused, and the neighbor can seek redress in court.
The lawyers at ARROWS law firm represent clients in cases where improper drainage has caused extensive property damage.
Easements and Neighbors' Rights
The issue of rainwater also significantly affects neighbors' rights as regulated in the Civil Code.
Eavesdrip Easement
A landowner may have an obligation to tolerate water from a neighboring roof flowing onto their property if an easement (a real burden) has been established for this purpose. However, without a valid legal title, such as a contract or prescription, you do not have the right to discharge water onto a neighbor's property.
Right to Rainwater Runoff
A landowner onto whose property water naturally flows from a neighboring, higher-lying property must accept it. However, there must be no intentional diversion of water without an agreement or easement. If a neighbor modifies the terrain in such a way that water newly flows to your property and causes damage, you have the right to defend yourself and demand an adjustment.
Subsidy Support: New Green Savings
The state encourages the use of rainwater through the New Green Savings subsidy program.
What Can Be Financed
A contribution can be obtained for the purchase of a rainwater retention tank, with the subsidy covering up to 50% of eligible expenses. The amount of support depends on how the water is used, i.e., whether it is only for watering the garden or also for flushing toilets in the house.
Conditions
The applicant can be the owner of a family or apartment house, and the program supports both new constructions and renovations. For new constructions, support is usually conditional on the water also being used inside the house, not just for watering.
Although the administrative process has been simplified in some calls, an expert technical calculation is still necessary for the correct system design and trouble-free operation. You will always need it for the building permit process.
Conclusion
Rainwater management is currently an indispensable legal obligation. Ignoring the law can lead to high fines, problems with final building approval, and costly neighbor disputes. The correct procedure includes verifying the possibility of infiltration, designing a technical solution, obtaining a permit, and subsequent maintenance.
The lawyers at ARROWS law firm handle this agenda comprehensively, from drafting easement agreements to representing clients in disputes over damages. Our experience helps clients avoid complications and defend their positions in administrative proceedings.
If you want to realize your project safely, contact ARROWS law firm. We will help you navigate the legislation and prevent future problems.
About the author
Disclaimer:
The information contained in this article is for general informational purposes only and serves as a basic guide to the issue as of 2026. Although we strive for maximum accuracy, laws and their interpretation evolve over time. We are ARROWS Law Firm, a member of the Czech Bar Association (our supervisory authority), and for the maximum security of our clients, we are insured for professional liability with a limit of CZK 350,000,000. To verify the current wording of the regulations and their application to your specific situation, it is necessary to contact ARROWS Law Firm directly (consultation@arws.cz). We are not liable for any damages arising from the independent use of the information in this article without prior individual legal consultation.