Cesspit and household wastewater treatment plant

A cesspit (žumpa, a sealed holding tank) is a watertight tank that collects waste water from the house and is emptied regularly. A household wastewater treatment plant (domovní ČOV) treats the water mechanically and biologically and discharges it into surface water or, through soil layers, into groundwater. Both are used where a house is not connected to a public sewer. A septic tank, from which partly treated water flows out, is neither a cesspit nor a treatment plant.

When a cesspit is allowed

The Water Act requires builders of new buildings to drain waste water into a sewer. Where there is none, treatment with discharge comes next, and a cesspit only where no other solution is technically feasible (Section 5(3)). The building authority may order an owner to connect to the sewer where this is technically possible.

Cesspit: emptying and records

A cesspit must be watertight, without an outflow and ventilated. Its contents may only be taken to a wastewater treatment plant, by the plant operator or a licensed company. On request of the water authority or the Czech Environmental Inspectorate, whoever uses the cesspit must show emptying receipts for the last two calendar years (Section 38(7) of the Water Act). A cesspit is not a water works; it is a structure permitted by the building authority.

Household plant: structure and discharge permit

A treatment plant for up to 50 population equivalents is a water works and, under the Building Act, a simple structure permitted by the building authority. Operating it also requires a waste water discharge permit from the water authority of the municipality with extended powers. It is issued for a limited period of at most 10 years and must then be renewed. Discharge into groundwater is allowed only where discharge into surface water is not possible, and only with a hydrogeologist's favourable opinion. Since 1 August 2025, small plants do not need occupancy approval.

Example

An illustrative calculation following Ministry of the Environment guidance: four people with a standard water use of 35 m³ per person per year produce about 140 m³ of waste water a year. A 10 m³ cesspit must therefore be emptied about 14 times a year.

What to ask for when buying

• for a cesspit, emptying receipts for the last two years,
• for a treatment plant, the building permit and a valid discharge permit with its expiry date,
• whether the municipality plans a sewer.

A discharge permit tied to the house passes to the new owner if the house keeps serving the same purpose; the transfer must be notified to the water authority within 2 months. Under the construction requirements decree, new cesspits and treatment plants are placed at least 12 m from a well, or 30 m in permeable ground; the building authority may grant an exception.