Sand/oil separators are in ground tanks. They are designed for use by places like car washes and vehicle maintenance shops. They are meant to capture things like dirt, sand, sweepings and minor petroleum spills. Keeping them out of the public water system. Substances lighter than water, oil for example, will float. Substances like sand, which is heavier than water, will sink. Only the grey water should be able to flow into the wastewater system.
It’s important to have the sand/oil separator pumped on a regular basis. Not only can waste back up into your service line and cause odors and blockages, if they take up too much space they may siphoned through the outlet pipe. This would cause the waste to flow into the wastewater system. Overflowing separators could cause damage to the environment. Overflow can also lead to public health issues.
Each separator is different, and you should know holding capacity for the one at your facility. Make sure that the waste is not reaching a depth within 8 inches of the outlet pipe. You can judge the depth by using a long rod, often referred to as a “sludge judge”. Have your separator pumped regularly. Procrastination will cost you more in the long run.
Check with your local government for regulations on these tanks. Usually, you will need to keep records on site for a set amount of time. You will also need to have your separator tested regularly to ensure that it’s not hazardous waste.