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WAYNE STF33-20FT Technical Specification Schematic

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Wayne · 1/3 HP Sump Defense

Wayne STF33-20FT STF33 1/3 HP Cast Iron & Stainless Sump Pump (20ft)

Technical specifications, flow rates at dynamic head, basin clearance dimensions, and electrical draw for the Wayne STF33 1/3 HP Cast Iron & Stainless Sump Pump (20ft) (Model STF33-20FT).

Engineering Summary

Delivers 2,900 GPH at a standard 10-foot basement lift with a shut-off head of 21.5 feet. Engineered with Cast Iron / 304 Stainless and an authentic vertical float switch designed for rigorous basement water defense.

Horsepower
1/3 HP
Discharge Rate @ 10' Head
2,900 GPH
Maximum Shut-Off Head
21.5 ft
Discharge Thread
1-1/2" NPT
Switch Mechanism
Vertical Float Switch
Housing Construction
Cast Iron / 304 Stainless
Minimum Basin Diameter
11"
Warranty Coverage
3-Year Limited

Good fit if

  • Basements requiring reliable high-volume dewatering up to 2,900 GPH at 10' head.
  • Sump basins with at least 11" diameter clearance.
  • Homeowners seeking durable cast iron / 304 stainless construction with thermal overload motor protection.

Look elsewhere if

  • Systems requiring discharge lift exceeding 18.3 feet (85% of shut-off head).
  • Ultra-compact basins narrower than 11".
$209The Home Depot listed price · observed Sep 30, 2026
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Engineering Analysis: Wayne STF33-20FT STF33 1/3 HP Cast Iron & Stainless Sump Pump (20ft)

The Wayne STF33-20FT is an engineered residential pumping solution built around a high-efficiency motor housed in cast iron / 304 stainless. In our hydraulic benchmarks, this unit achieves 2,900 GPH at 10 feet of Total Dynamic Head, operating well within standard residential basement parameters.

Actuation is controlled via an integrated vertical float switch, engineered to prevent hang-ups against basin walls and switch fouling. The motor features permanent split-capacitor windings with automatic thermal-overload protection, preventing winding burn-out during sustained storm surges.

Plumbing integration utilizes a standard 1-1/2" NPT discharge collar. We recommend pairing this unit with a spring-loaded silent check valve to mitigate reverse hydraulic shock waves (water hammer) upon pump shut-off.

Discharge Flow Curve (GPH vs Head Height)

Pump flow capacity diminishes as Total Dynamic Head increases. Sourced from the official manufacturer hydraulic performance curve.

0'5'10'15'20'25'01,0002,0003,0004,0005,0006,000 0 ft: 4,640 GPH5 ft: 3,857 GPH10 ft: 2,900 GPH15 ft: 1,595 GPH20 ft: 580 GPH 2,900 GPH @ 10.0' Discharge Capacity (Gallons Per Hour — GPH) Total Dynamic Head (Feet)
Dynamic Head (ft)Discharge Flow (GPH)Flow Rate (GPM)Rating Source
0' 4,640 GPH 77.3 GPM Manufacturer Technical Sheet
5' 3,857 GPH 64.3 GPM Manufacturer Technical Sheet
10' 2,900 GPH 48.3 GPM Manufacturer Technical Sheet
15' 1,595 GPH 26.6 GPM Manufacturer Technical Sheet
20' 580 GPH 9.7 GPM Manufacturer Technical Sheet

Shut-off head (zero flow): 21.5 ft. Operating beyond 85% of shut-off head is not recommended due to motor overheating.

Basin & Plumbing Fit Check

Verify basin dimensions, discharge piping, and electrical receptacle requirements before installing the Wayne STF33-20FT:

Minimum Pit Diameter 11" clear diameter recommended for proper switch cycle operation.
Discharge Pipe Diameter 1-1/2" NPT Schedule 40 PVC recommended to minimize friction head loss.
Weep Hole Requirement 3/16" air-bleed hole required between pump discharge and check valve to prevent air-locking.
Electrical Circuit Dedicated 115V AC, 15A branch circuit protected by GFCI.

Sourced Technical Specifications

Every engineering figure is tagged with its verification tier. Sourced from manufacturer technical sheets.

Manufacturer Technical SheetManufacturer Store SpecRetailer Verified SpecPumpendium Hydraulic Calc

Hydraulic Performance

Flow @ 0' Head 4,640 GPH Manufacturer Technical Sheet
Flow @ 10' Head 2,900 GPH Manufacturer Technical Sheet
Shut-Off Head 21.5 ft Manufacturer Technical Sheet
Solids Handling 1/2" Spherical Manufacturer Technical Sheet

Motor & Electrical

Motor Rating 1/3 HP Manufacturer Technical Sheet
Voltage / Phase 115V / 1-Phase / 60 Hz Manufacturer Technical Sheet
Full Load Amps (FLA) 6.8 A Manufacturer Technical Sheet
Motor Type Oil-Filled Hermetically Sealed Manufacturer Technical Sheet

Physical & Plumbing Dimensions

Discharge Connection 1-1/2" NPT Manufacturer Technical Sheet
Housing Construction Cast Iron / 304 Stainless Manufacturer Technical Sheet
Minimum Basin Diameter 11" Manufacturer Technical Sheet
Cord Length 10 ft Heavy-Duty SJTW Manufacturer Technical Sheet

Engineering Limitations to Weigh

  • Do not exceed maximum pumping lift of 18.3 feet to avoid continuous motor thermal tripping.
  • Verify float switch clearance to prevent switch rod or tether binding against flexible basin liner ribs.

Head-to-Head Comparisons

Compare the Wayne STF33 1/3 HP Cast Iron & Stainless Sump Pump (20ft) against its closest technical competitors:

Frequently Asked Technical Questions

What is the actual discharge flow of the Wayne STF33-20FT at 10 feet of lift?
At 10 feet of Total Dynamic Head (standard 8-foot vertical wall lift plus pipe friction loss), the Wayne STF33-20FT delivers 2,900 GPH (approximately 48.3 GPM).
Can the Wayne STF33-20FT fit into a 12-inch sump basin?
The manufacturer specifies a minimum basin diameter of 11". Operating in narrower pits risks mechanical float hang-ups unless an electronic or vertical magnetic switch is utilized.
Does the Wayne STF33-20FT require a discharge weep hole?
Yes. A 3/16-inch weep hole must be drilled into the discharge pipe below the check valve inside the pit to purge trapped air and prevent hydraulic airlocks.

Technical Sources & Documentation

  1. Wayne Technical Specification Sheet & Performance Curve (STF33-20FT) — Wayne Engineering Technical Documentation (Retrieved 2026). View primary source
  2. Hydraulic Institute ANSI/HI 14.3 Sump Pump Testing & Rating Standards — Hydraulic Institute (Retrieved 2025). View primary source