Vehicle washing greese and oil trap design 1

This design is problematic. You have a sand filter in the system which will get clogged quickly with residue.

Your flow is relatively small and there are lots of commercially available oil/water separators on the market that would be more efficient and likely less expensive than building the tank you have shown.

Many oil/water separators work on a flat plate/lamellar flow process...others work by vertical baffles with liquid flowing from the bottom to top through weirs or slots at the bottom of the baffles and the oil/grease floats to the top. It is important that the flow be very slow through these devices.


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Funny, I was just sizing one for a 3 bay garage for our public works department. By our State Plumbing Code I show a need for a 184 gallon unit and readily found commercial units at 250 gallons. In my case I'm just filtering floor drains and am not concerned with maintaining a specific flow rate through the unit.