A sand interceptor is a below-floor tank that settles out sand, grit, and heavy solids from wastewater before it enters the sewer. The heavy material sinks and cleaner water flows out the top. Car washes, garages, and industrial floors use one to keep grit from clogging the drain lines.
A sand interceptor is a below-floor tank that traps sand, grit, and other heavy solids before they reach the sewer. Wastewater flows in and slows down. The heavy material sinks to the bottom, and the cleaner water flows out the top. Car washes, auto shops, and industrial floors use one to keep grit out of the drain lines.
How a sand interceptor works
The device works on settling. Heavy solids sink in still water. Wastewater enters a large tank set into the floor and slows down. In that calm space, sand, grit, mud, and metal shavings drop to the bottom. An interior baffle splits the tank into two sections. That baffle stops flow from rushing straight across, so the solids have time to settle. The clean water leaves through an outlet near the top. Crews pump out the collected grit on a set schedule. Common models include the Zurn sand and sediment interceptor.
What the code requires
The Uniform Plumbing Code covers this in section 1016.0, Sand Interceptors. It calls for a sand interceptor wherever a drain carries solids heavier than water that could clog or damage the sewer. The unit must be readily accessible for cleaning. It must hold a water seal of at least 6 inches and be vented. The inlet needs a net free opening of at least 2 square feet, with more area added as flow goes up. Code allows brick, concrete, coated steel, or other watertight material.
Not a grease or oil interceptor
A sand interceptor is not a grease interceptor or an oil-water separator. All three sit between a drain and the sewer, but each catches a different waste. A grease trap holds kitchen fats and food waste. An oil-water separator floats off petroleum and fuel. A sand interceptor drops out heavy grit and solids. Car washes and garages often run a sand interceptor and an oil separator in series. A commercial plumber can size and install the right unit.