Generac Power Systems ST20

Questions and Answers:

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Eric PhillipsAug 12, 2025
What to do if my Generac Power Systems Water Pump will not pump?
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  Casey BrownAug 12, 2025
  If your Generac Power Systems Water Pump isn't pumping, there could be several reasons. First, check for air leaks in the suction hose, ensuring it's double-clamped at joints, the clamps are tight, fittings have thread compound and are tight, and the hose has no nicks or cuts. Also, the suction or discharge lines may be blocked, so check the hoses and filter. Ensure the end of the suction line is fully submerged; if not, increase its length or move the pump closer to the liquid source. Finally, the total head might be too high; reduce it or use a higher head pump.
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Kyle SavageAug 16, 2025
What to do if my Generac Power Systems Water Pump does not perform well?
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  Lisa SalasAug 16, 2025
  If your Generac Power Systems Water Pump's performance is lacking, start by checking for debris buildup restricting the flow; clean the hoses, fittings, and filter. Ensure the suction hose end is fully submerged. Inspect the impeller for excessive wear and replace if needed. Check for a damaged seal, indicated by liquid leaking from the adapter's middle, and replace it. Also, check the suction hose for air pockets or leaks. Clean out a clogged impeller by removing the casing. Finally, ensure the engine throttle is set to the FAST position.
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mbushAug 20, 2025
What to do if my Generac Power Systems ST20 Water Pump will not start?
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  Michael HarrisAug 20, 2025
  If your Generac Power Systems Water Pump refuses to start, first, allow the engine to cool for 2 minutes, then ensure there's fuel in the tank. Replace a faulty spark plug. Check that the fuel valve lever and the ignition switch are in the ON position. Lastly, make sure the choke is in the correct position; slide the choke lever to the CHOKE position.
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Timothy GarciaAug 25, 2025
Why does my Generac Power Systems ST20 Water Pump shut down during operation?
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  Charles MartinAug 25, 2025
  Your Generac Power Systems Water Pump might shut down during operation for a couple of reasons. It could be out of fuel; allow the engine to cool for 2 minutes, then fill the fuel tank. Alternatively, the low oil sensor might be shutting down the unit. Ensure the unit is on a flat surface and check the oil level, adding more if necessary.
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Tamara BallAug 27, 2025
Why does my Generac Power Systems ST20 Water Pump start but runs roughly?
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  Nicholas PowellAug 27, 2025
  If your Generac Power Systems Water Pump starts but runs roughly, the choke might be in the wrong position; slide the choke lever to the RUN position. Ensure the spark plug wire is securely attached. Replace a faulty spark plug. Drain the fuel tank and carburetor, then refill with fresh fuel if the current fuel is contaminated with water or debris.
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Ryan ClarkAug 31, 2025
Why Generac Power Systems Water Pump loses prime?
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  webbjeremyAug 31, 2025
  A Generac Power Systems Water Pump may lose its prime if the water level drops below the end of the suction line. To resolve this, either increase the length of the suction line or move the pump closer to the water source.
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deborah71Sep 3, 2025
How to prime Generac Power Systems Water Pump faster?
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  Melvin WilliamsSep 3, 2025
  Priming your Generac Power Systems Water Pump can be sped up by moving the pump closer to the liquid source, especially if the suction line is long. Also, check the suction line for loose connections or air leaks, and ensure the suction hose is fully submerged.
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Anthony RamosSep 7, 2025
Why Generac Power Systems ST20 Water Pump will not prime?
- M
  Melissa MasonSep 7, 2025
  If your Generac Power Systems Water Pump won't prime, it might be due to excessive suction lift. Try moving the pump closer to the liquid source.

Generac Power Systems ST20 Specifications

General

Model	ST20
Inlet Size	2 in
Outlet Size	2 in
Maximum Flow Rate	158 GPM
Maximum Suction Lift	26 ft
Self-Priming	Yes
Type	Water Pump
Engine	Generac OHV
Max Head	95 ft

Summary

Introduction

Contacting Generac

Provides contact information for Generac Customer Service via phone and internet.

Safety

Exhaust Hazard Safety

Details dangers of carbon monoxide from engine exhaust and safe operating practices.

Exhaust Hazards and Precautions

Explains risks of carbon monoxide and requires outdoor operation.

Electrical Shock Hazard

Warns about the risk of electrocution from contact with power sources.

Hot Surfaces Hazard

Alerts to burns from hot parts and exhaust gases igniting combustibles.

Fire Hazards

Details flammability of fuel and vapors, and precautions during fueling.

Hearing Protection Hazard

Recommends hearing protection due to objectionable noise levels.

Fall Hazard

Warns about slippery surfaces and the risk of falling.

Moving Parts Hazard

Highlights risks of entanglement with rotating parts and protective clothing.

Kickback Hazard

Explains starter cord kickback risk and safe pulling technique.

Spark Hazards

Warns about unintentional sparking causing fire or electric shock.

Splash Hazards

Warns of eye injury risk from spray and recommends safety goggles.

General Information

Know Your Water Pump Components

Identifies key components and controls of the water pump using diagrams.

Product Specifications

Provides technical specifications for CW15K and ST20K models.

Emissions Information

Details compliance with EPA and CARB emission standards and tamper warnings.

High Altitude Operation

Notes potential influence of higher altitudes on the engine's fuel system.

Unpacking and Parts Check

Instructions for removing parts from the carton and verifying all items are present.

Set-up and Assembly

Assembling the Water Pump

Step-by-step instructions for attaching vibration mounts, handle, and wheels.

Adding Engine Oil

Guides on checking and filling engine oil to the correct level.

Fuel Requirements and Adding Fuel

Specifies gasoline requirements and procedures for safely adding fuel.

Connecting Suction and Discharge Hoses

Instructions for attaching hoses, barbs, clamps, and filter.

Priming the Water Pump

Procedure for filling the pump chamber with water before operation.

Operation

Water Pump Location and Clearances

Guidance on placing the pump outdoors with adequate clearance and air movement.

Pre-Start Checklist

Ensures the unit is ready for operation by checking safety, oil, fuel, and hoses.

Starting the Water Pump

General steps for starting the water pump engine.

Starting the CW15 Water Pump

Step-by-step guide for initiating the CW15 model's engine.

Starting the ST20 Water Pump

Step-by-step guide for initiating the ST20 model's engine.

Stopping the Water Pump

Procedures for safely shutting down the water pump engine.

Maintenance

Maintenance Recommendations

General advice on regular maintenance for performance and longevity.

Maintenance Schedule

Provides recommended service intervals for various maintenance tasks.

Emissions Control Maintenance

Details on maintenance of emissions control devices and authorized service.

Water Pump Maintenance

Covers cleaning debris, checking hose filter, and inspecting hoses.

Checking the Hose Filter

Instructions for examining and cleaning or replacing the suction hose filter.

Checking Hoses

Guide to inspecting hoses for leaks, damage, or wear.

Engine Maintenance

General warnings and procedures for engine maintenance tasks.

Engine Oil Recommendations

Specifies recommended oil types and viscosity for engine lubrication.

Checking Engine Oil Level

Step-by-step guide to checking the engine oil level using the dipstick.

Adding Engine Oil

Instructions for filling the engine oil to the correct level.

Changing Engine Oil

Procedure for draining and refilling engine oil, especially in harsh conditions.

Servicing the Air Cleaner

Steps for cleaning or replacing the air filter to maintain engine performance.

Servicing the Spark Plug

Guide to inspecting, gapping, and replacing the spark plug.

After Each Use Procedures

Tasks to perform after every use to prevent damage and ensure longevity.

Long Term Storage

Preparations for storing the water pump for over 30 days.

Protecting the Fuel System for Storage

Instructions for stabilizing fuel to prevent degradation during storage.

Protecting the Engine for Storage

Steps to protect the engine's internal components during storage.

Changing Engine Oil for Storage

Procedure for changing oil before long-term storage.

Protecting the Pump for Storage

Methods to prevent pump damage from mineral deposits or freezing.

Other Storage Instructions

Additional advice on fuel storage, unit covering, and storage location.

Transporting and Tipping

Warning against operating or transporting the unit at an angle greater than 15 degrees.

Troubleshooting

Troubleshooting Guide

Lists common problems, their causes, and recommended corrective actions.

Generac Power Systems ST20

Table of Contents

Questions and Answers:

Generac Power Systems ST20 Specifications

Summary

Introduction

Contacting Generac

Safety

Exhaust Hazard Safety

Exhaust Hazards and Precautions

Electrical Shock Hazard

Hot Surfaces Hazard

Fire Hazards

Hearing Protection Hazard

Fall Hazard

Moving Parts Hazard

Kickback Hazard

Spark Hazards

Splash Hazards

General Information

Know Your Water Pump Components

Product Specifications

Emissions Information

High Altitude Operation

Unpacking and Parts Check

Set-up and Assembly

Assembling the Water Pump

Adding Engine Oil

Fuel Requirements and Adding Fuel

Connecting Suction and Discharge Hoses

Priming the Water Pump

Operation

Water Pump Location and Clearances

Pre-Start Checklist

Starting the Water Pump

Starting the CW15 Water Pump

Starting the ST20 Water Pump

Stopping the Water Pump

Maintenance

Maintenance Recommendations

Maintenance Schedule

Emissions Control Maintenance

Water Pump Maintenance

Checking the Hose Filter

Checking Hoses

Engine Maintenance

Engine Oil Recommendations

Checking Engine Oil Level

Adding Engine Oil

Changing Engine Oil

Servicing the Air Cleaner

Servicing the Spark Plug

After Each Use Procedures

Long Term Storage

Protecting the Fuel System for Storage

Protecting the Engine for Storage

Changing Engine Oil for Storage

Protecting the Pump for Storage

Other Storage Instructions

Transporting and Tipping

Troubleshooting

Troubleshooting Guide