Head-to-Head Comparison · 1/3 HP Class

Liberty Pumps 257 1/3 HP Cast Iron Sump Pump vs. Liberty Pumps S37 1/3 HP Stainless Steel Sump Pump (pro-kit)

Engineering comparison between the Liberty Pumps 257 1/3 HP Cast Iron Sump Pump and Liberty Pumps S37 1/3 HP Stainless Steel Sump Pump (pro-kit). Flow curves, switch durability, and technical verdict.

Liberty Pumps

257 1/3 HP Cast Iron Sump Pump

LIBERTY PUMPS 257 Technical Specification Schematic
$264SupplyHouse listed price · observed Sep 30, 2026
Liberty Pumps

S37 1/3 HP Stainless Steel Sump Pump (pro-kit)

LIBERTY PUMPS S37-PRO-KIT Technical Specification Schematic
$304SupplyHouse listed price · observed Sep 30, 2026
The Technical Verdict

The Liberty Pumps 257 1/3 HP Cast Iron Sump Pump delivers 2,040 GPH at 10' head compared to 2,100 GPH for the Liberty Pumps S37 1/3 HP Stainless Steel Sump Pump (pro-kit). If your basement requires maximum flow throughput, the Liberty Pumps holds the hydraulic advantage. For tight sump pits, compare the minimum basin clearances: 10" vs 10".

Specification Comparison Matrix

Specification Liberty Pumps 257 1/3 HP Cast Iron Sump Pump Liberty Pumps S37 1/3 HP Stainless Steel Sump Pump (pro-kit) Advantage
Discharge Flow @ 10' Head 2,040 GPH 2,100 GPH Liberty Pumps +60 GPH
Shut-Off Head 21.0 ft 22.0 ft Liberty Pumps +1.0 ft
Switch Mechanism VMF Magnetically-Coupled Vertical Float VMF Magnetically Coupled Float Vertical Clearance
Housing Material Class 25 Cast Iron Stainless Steel / Cast Iron Thermal Heat Sink
Minimum Basin Diameter 10" 10" Basin Fit
List Price $264.00 $304.00 Lower Initial Cost

Choose 257 1/3 HP Cast Iron Sump Pump If:

  • You require 2,040 GPH discharge capacity at standard 10' head.
  • Your installation prioritizes Class 25 Cast Iron for continuous motor heat dissipation.
  • You prefer the VMF Magnetically-Coupled Vertical Float switch mechanism.

Choose S37 1/3 HP Stainless Steel Sump Pump (pro-kit) If:

  • You need 2,100 GPH flow capacity at 10' dynamic head.
  • Your sump pit accommodates a 10" clearance footprint.
  • You favor the VMF Magnetically Coupled Float actuation design.

Hydraulic Performance & Head Sizing

When operating at 10 feet of Total Dynamic Head, the Liberty Pumps 257 delivers 2,040 GPH versus 2,100 GPH for the Liberty Pumps S37-PRO-KIT. Pumping capacity curves indicate that both models handle standard residential foundation drainage effortlessly.

Switch Technology & Pit Clearance

The Liberty Pumps employs a VMF Magnetically-Coupled Vertical Float requiring a 10" pit, whereas the Liberty Pumps utilizes a VMF Magnetically Coupled Float suited for basins with at least 10" clearance. Ensuring your pit allows uninhibited float movement is essential to preventing switch hang-ups.