In Örebro municipality, Sweden, the municipal environmental organization performs an inspection of on-site wastewater treatment systems after receiving a control report and photo documentation from the homeowner. In this project 57 soil treatment systems and 50 systems with prefabricated treatment plants were inspected to evaluate the methods and instruments of the inspection, and to draw conclusions of the applicability of different checkpoints in the inspection. Furthermore, deficiencies of the treatment systems were complied, and suggestions were made of how to develop the control report, permit process and the follow-up of the permits. Some of the checkpoints, methods and instruments of the inspections were concluded to be suitable without changes, but some changes were also suggested and some of the checkpoints were considered not to be recommended as a standard in every inspection. When it comes to recommended changes, the size of the soil treatment system was one example that was hard to measure in the field. It is therefore important to make sure that the homeowner provides photo documentation with a measuring tape that show the size of the soil treatment system. Örebro municipality also needs to be tougher on requiring photo documentation on precipitation units and phosphorus traps as well as photo documentation that shows whether new pipes have been connected. The other suggested changes include service contracts, measurements of water levels in vent pipes and drainage pipes, general improvements of the control report and the photo documentation etc. Among the checkpoints that was not recommended as a standard in every inspection was testing the ventilation with a smoke cartridge, to measure the pH and temperature in prefabricated treatment plants and septic tanks, to measure and compare the depth of the distribution well with the depth of the drainage pipe at soil treatment systems and to measure groundwater level in the field. The connection between pH/temperature and functional problems needs to be clarified – preferably through a future study. The other checkpoints were considered difficult to perform in the field and was therefore recommended to be performed when there are signs of functional problems and not as a standard part of inspection. For the permit process, it was proposed to review the conditions, to clarify requirements for documentation on groundwater and service and to provide information on how the conditions are followed up. Among other suggestions for improvement were that it would be desirable to have access to a database or other documentation in the field with quick access to product information about different types of prefabricated treatment plants.