3LSIS/4LSIS Built-in Screw Solar Submersible Pump

Model Interpretation:
3/4: Represents the pump body diameter (3 inches ≈ 76mm, 4 inches ≈ 100mm).
L: Vertical.
S: Screw.
I: Usually represents "In-well" or "Immersion".
S: Stainless Steel casing/stator housing.

Core Configuration: Single-screw submersible pump.
Core Difference: Unlike centrifugal pumps (which use rotation to throw water), screw pumps rely on a rotor (screw) rotating within a stator (rubber bushing), forming sealed chambers that "push" the water up like peristalsis.
Core Working Principle: Positive displacement + Low speed, high torque
The LSIS series operates on the principle of "slow and powerful, accepting all comers":
Meshing Seal: The core of the pump is a metal rotor (screw) and a rubber stator. As the rotor rotates within the stator, a continuous sealing line is formed.
Axial Propulsion: As the rotor rotates, the sealed chambers move from the suction end to the discharge end. The liquid is enclosed in the chambers and smoothly "pushed" out of the wellhead.
Low-Speed ​​Operation: Compared to the high rotational speed of centrifugal pumps, screw pumps typically operate at lower speeds. Combined with a brushless DC motor, it provides extremely high starting torque, making it ideal for solar power (low starting current).
Core Features: Resistant to impurities, wear-resistant, capable of pumping viscous liquids

Feature Detailed Description
Extremely High Wear Resistance: A core advantage. Screw pumps are insensitive to sand and particles. Even with high sand content in well water, screw pumps can operate normally, and their lifespan is much longer than centrifugal pumps (the impeller of a centrifugal pump will be worn down by sand, while the screw pump "pushes" the sand along).
Pumping High-Viscosity Media: Centrifugal pumps lose pressure when pumping mud, while screw pumps excel at pumping sludge, mud, oil-water mixtures, and other high-viscosity liquids. The higher the viscosity, the better its sealing performance.
Strong Self-Priming Capability: Screw pumps have excellent self-priming capabilities. For shallow wells or applications installed on the ground, they can easily draw water (although this advantage is more evident at the moment of startup when used as a submersible pump).
Stable and Pulsation-Free Flow: Due to volumetric displacement, the water flow is very stable, without the violent water hammer phenomenon of centrifugal pumps, resulting in less impact on the pipeline.

Typical Application Scenarios:
The LSIS series is an expert in handling harsh environments, sewage, and sludge:
Deep well water extraction with sand:
Suitable for old, deep wells with unstable well walls and containing a large amount of sand or rust.
Sewage/sludge discharge:
Suitable for livestock farm manure treatment, septic tank cleaning, municipal sewage discharge, etc.
Industrial wastewater/oil-water separation:
Used for conveying industrial wastewater containing oil, chemicals, or suspended solids.
Biogas slurry extraction:
In biogas projects, used for extracting biogas slurry containing a large amount of solid suspended matter.

Selection and Usage Suggestions:
Strictly prohibit dry running (critical):
The rubber stator of the screw pump requires liquid for lubrication and cooling. It is absolutely forbidden to run without liquid for a long time, otherwise, the stator will quickly melt and become unusable due to frictional heat. It is recommended to equip a water shortage protection controller.
Temperature limitations:
The rubber stator is not resistant to high temperatures. The temperature of the conveyed medium should generally not exceed 80℃-100℃. If high-temperature liquids need to be conveyed, please choose a stator made of special materials.
Relatively small flow rate:
Compared with centrifugal pumps of the same power (such as the LZSU series), the flow rate of screw pumps is usually smaller, but its head (pressure) can be very high. It is more suitable for "steady flow" scenarios.
Reverse rotation problem:
Screw pumps usually have strict requirements for the direction of rotation. The motor rotation direction must be confirmed during wiring; reverse rotation will damage the stator.

The 3LSIS/4LSIS series is the "off-road vehicle" among solar water pumps. It doesn't pursue speed and flow rate like centrifugal pumps (LSG/LHF), but it is robust and durable. If your well water is very dirty, contains a lot of sand, or you need to pump sludge or viscous liquids, then the LSIS series is the irreplaceable best choice.