To avoid harmful substances it is important that emissions such as oil, gasoline, grease and sludge are cleaned by oil separators to reduce damage to the human health and the environment. But also to prevent high levels of oil from waste water to sewage treatment plants which can disturb the purification process. The aim with this work is to find out that the municipalities fulfill the requirements in the environmental framework. By supervising the 5-year inspection of oil separators according to SS EN 858 on the stormwater and wastewater network. To find out this, inquiries were sent by e-mail to all 290 municipalities in Sweden. The results show that the inventories of oil separators have not been carried out to the proper extent. The municipalities can follow the supervision pursued according to the environmental guidelines and environmental goals but an inventory is also needed to know how many oil separators are present in the municipalities. The oil separators are usually controlled with other supervisions. A 5 - year inspection of oil separators that were sufficiently good has only been made by 2 municipalities. 5 – year inspection must be carried out even if the operations have not been running for 5 years. The conclusion from this study is that oil separators have been a neglected area in most municipalities. Hopefully this inquiry can be a reminder to start with inventories in those municipalities.