A constant level lubricator is used to maintain the oil level in a piece of equipment that naturally depletes fluid through use, wear, friction, or evaporation. Bearings, gearboxes, and pillow blocks typically require oil replenishment, especially when used in environments that are dirty or where heat is a factor. Typical industries that utilize constant level lubricators include paper mills, cement plants, coal handling facilities, wastewater treatment, nuclear plants, and mining operations. A constant level lubricator operates without a power source or moving mechanical parts. It relies on the liquid seal principle to maintain a fixed liquid level in a bearing housing or gear box. It can function reliably over long periods with little or no monitoring. When piped to a bearing, gearbox, or similar piece of equipment, the height of the constant level oiler is critical. The oil level line must align with the optimal fluid level in the main equipment. The air vent on the lubricator should be piped into the main equipment above the fluid level to equalize the pressure between the lubricator and the main equipment.