Tyhjennysvesi

Tyhjennysvesi is a Finnish term for water that is discharged when a container, tank, or system is emptied. It may originate from household rainwater tanks, septic systems, wastewater-treatment units, boilers, or cleaning operations in industrial facilities. The exact composition varies with the source, but tyhjennysvesi commonly contains sediments, organic matter, nutrients such as nitrogen and phosphorus, detergents or cleaning chemicals, oils, and dissolved minerals. Temperature and pH can differ, and in coastal areas the water may be influenced by salinity.

In environmental management, tyhjennysvesi requires appropriate handling to prevent pollution. Many municipalities regulate its disposal; typically clean or lightly contaminated tyhjennysvesi can be discharged to an appropriate stormwater network, an infiltration field, or a wastewater system according to local rules. More contaminated streams may require treatment, capture for reuse, or disposal through designated facilities. Practical handling includes preventing spills, using sedimentation or filtration steps, and avoiding direct release to sensitive natural watercourses. For rainwater tanks or septic systems, regular maintenance and adherence to local guidelines are advised.

Etymology: tyhjennysvesi combines tyhjennys (emptying) and vesi (water). The term is widely used in Finnish water management and construction sectors to describe discharge water from emptied installations.

See also: greywater, wastewater, stormwater.