Before you begin. This procedure is general reference information, not professional advice. Equipment varies by manufacturer, model, and year. Always follow the documentation supplied with your equipment — where it differs from this page, follow the manufacturer. Verify that you have the tools, the working conditions, and the ability to do this task safely. If anything is unclear, if the equipment is damaged, or if the task exceeds your experience, stop and use a qualified professional. You are responsible for your own safety and for the outcome. This site accepts no liability for any loss, damage, or injury arising from the use of this information.
Specifications marked unverified could not be traced to a manufacturer source. Do not rely on them — obtain the value from your equipment documentation.
Summary
Prevent pump damage by testing water supply adequacy before starting a pressure washer. Measure inlet water pressure and flow rate using a bucket test and a stopwatch. Compare results to your machine's minimum requirements from its manual. Use the appropriate inlet hose diameter for your machine's rated flow.
Necessary equipment
| Item | Note |
|---|---|
| 5-gallon bucket | Use the bucket for the flow rate test. |
| Stopwatch or timer | Record the time for the bucket test. |
| Pressure gauge | Measure the inlet pressure at the water source. |
| Water material | Use the water cold only. Temperature must not exceed 100°F. |
Specifications
No tier-1 source was found for this value. Take it from the documentation supplied with your equipment.
No tier-1 source was found for this value. Take it from the documentation supplied with your equipment.
No tier-1 source was found for this value. Take it from the documentation supplied with your equipment.
Procedure
Estimated 16 min to 23 min
DO NOT START THE PRESSURE WASHER IF WATER FLOW IS LOW.
Without adequate water, the pump draws air. Pump seals fail.
- Read the documentation for your pressure washer.3mReport a problem with step 1, Procedure
- Write down the minimum flow rate in gallons per minute.
- Write down the minimum inlet pressure in PSI.
- Do the bucket test at the location where you will use the washer.3mReport a problem with step 2, Procedure
- Turn on the water supply at the tap.
- Place a 5-gallon bucket under the water hose.
- Start a stopwatch when water starts to flow.
- Stop the stopwatch when the bucket is full.
- Calculate the water flow rate in gallons per minute.1mReport a problem with step 3, Procedure
- Divide 300 by the fill time in seconds.
- The result is the water flow rate.
- Compare your flow rate to the minimum stated in your manual.<1mReport a problem with step 4, Procedure
- If the flow rate is adequate, go to step 5.
- If the flow rate is too low, locate a larger water source.
- Measure the water pressure at the tap with a pressure gauge.2mReport a problem with step 5, Procedure
- Connect the pressure gauge to the tap.
- Read the gauge display.
- Write down the pressure in PSI.
- Compare your measured inlet pressure to the minimum from your manual.<1mReport a problem with step 6, Procedure
- If pressure is adequate, your water supply is adequate.
- If pressure is low, locate a larger water source.
- Inspect the inlet hose for any damage.2mReport a problem with step 7, Procedure
- Look for kinks, cracks, holes and blockages.
- Feel the hose for soft spots and weak areas.
- Replace the hose if you see damage.
- Compare the inlet hose bore diameter with your manual.2mReport a problem with step 8, Procedure
- Your manual states the diameter you need.
- Use only the diameter stated in your manual.
- A hose with insufficient bore reduces the water flow.
- Connect the inlet hose to the washer.2mReport a problem with step 9, Procedure
- Both the flow and the pressure must meet the minimum values.
- If the flow is low, do not start the washer.
- If the pressure is low, do not start the washer.
- Use an alternative water source if needed.
Terminology
This page uses one term for each item and holds it throughout, as ASD-STE100 requires. Equipment sellers and other guides use the names below for the same parts.
- inlet flow rate
- Also called: no common alternatives
- inlet pressure
- Also called: no common alternatives
- pump starvation
- Also called: no common alternatives
- bucket test
- Also called: no common alternatives
When to use a professional
Do not start the pressure washer with low water supply. Contact a plumber or the manufacturer if your water source is inadequate.
Common questions
What happens if I run a pressure washer without adequate water supply?
When inlet water flow is too low, the pump draws air instead of water. Air in the pump system causes cavitation damage, seal failure, and pump overheating. Pump failure from water starvation is one of the most common pressure washer problems.
Why does inlet hose length matter?
Water pressure drops as it travels through a long hose. If your inlet hose is very long or has a small bore diameter, the pressure reaching the pump can fall below the minimum required even if tap pressure is adequate. Every foot of hose run adds pressure loss. Use the shortest hose possible and match the bore diameter to your machine's specification.
How accurate is the bucket test?
The bucket test is very accurate because it measures actual flow from your water source at the location and elevation where you will use the washer. Elevation, water line size, and distance from the source all affect pressure and flow. A bucket test completed at the location where you plan to work reflects real conditions better than a pressure gauge reading alone.
Can I use hot water in a pressure washer?
No. Pressure washer pump seals are designed for cold water only. Hot water damages seals and rubber components inside the pump. Check your machine manual for the maximum inlet water temperature, which is typically 100 degrees Fahrenheit. Always use cold water.
What do I do if my water source does not meet the minimum requirements?
Do not start the pressure washer. Running it with inadequate supply will destroy the pump. Consult your machine manual for alternative solutions, such as using a larger diameter water line, shortening the hose run, connecting to a larger water source like a well or storage tank, or using a booster pump. Contact the manufacturer if you are unsure.
Related procedures
- Clear a blocked pressure washer nozzle and inlet screen
- How to check and replace the fill hoses on a washing machine
- Inspect a pressure washer hose, couplings and O-rings before use
- How to winterize a pressure washer pump before freezing weather, and what to put in it
- How to use the soap or detergent injector on a pressure washer, and why nothing comes out of it
- How to choose the right pressure washer nozzle for the surface you are cleaning, and what the colours actually mean
Sources
Every specification on this page is traced to one of these sources. Tier 1 is a manufacturer document, a published standard, or a government safety authority. See Standards for the full tiering rule.
Revision history
Current version 1 · updated 2026-08-03 · next review due 2027-08-03
- v1 · 2026-08-03First publication.
Corrections to this page are listed in the public corrections log. Reports that are credible and not yet verified are listed in the public errata register, and an open one renders above the step it concerns.
Comments and corrections
Found an error? A correction with a manufacturer source is applied and logged publicly. You can also write to corrections@fixchecklist.com.
Every step above carries its own report control, which tags the report with that step so a correction reaches the right place. For anything about the procedure as a whole — the order of the sections, a step that is missing, something that did not match your equipment — use this: report something about this whole procedure.