Lemco Seals are Engineered to Control Drawdown and Stop Submersible Pumps From Sucking Air
The LEMCO SEAL helps control drawdown and it protects the submersible pump by keeping it submerged in water. The airtight Lemco Seal forces the submersible pump to draw from the aquifer below instead of lowering the static water level inside the well. During dry spells, when the static water level lowers naturally, cavitation and pump failure can result. Wells made in fine sand with screens are especially vulnerable to drawdown. Even when there seems to be plenty of water, fine sand and fine screens restrict water flow and cause excessive drawdown.
Because the seal is airtight, it accounts for negative pressure or suction on the well when the pump is running. This means it can increase well production. In the illustration, the submersible pump is submerged in water. Even though the water level has dropped below the pump inlet (on the outside of the well). To use an analogy, it's similar to sucking on a straw and raising the level of the liquid above the glass. The Lemco Seal makes it possible to raise the water level, inside the well, far above the water level outside the well casing, which makes it ideal for low water level and slow producing wells.