Introduction
Pump cavitation is one of the most common causes of premature pressure washer pump failure.
It occurs when insufficient water reaches the pump inlet, causing vapour bubbles to form inside the pump before collapsing under pressure. Although cavitation often begins as a minor operating issue, continued use can rapidly damage internal pump components.
This guide explains what cavitation is, why it occurs, how to recognise the warning signs and the operating practices that help prevent expensive pump damage.
What Is Pump Cavitation?
Professional pressure washer pumps are designed to receive a constant supply of clean water at the correct flow rate.
When the pump cannot receive enough water, inlet pressure falls below the vapour pressure of the water.
Tiny vapour bubbles form inside the pump and collapse as pressure increases through the pumping cycle.
These repeated implosions create microscopic shockwaves that gradually erode internal components.
Cavitation can affect:
- inlet valves
- valve seats
- ceramic pistons
- pump manifolds
- seals
- bearings
Even minor cavitation can significantly reduce pump service life if ignored.
What Causes Cavitation?
The most common causes include:
- restricted inlet hoses
- undersized water supply hoses
- blocked inlet strainers
- excessive suction lift
- collapsed hose linings
- partially closed supply valves
- inadequate mains water flow
- poorly designed supply tanks
- air leaks on suction fittings
- operating with insufficient water supply
Professional pressure washer pumps require unrestricted water flow at all times.
Common Symptoms
Typical signs include:
- knocking or hammering noises
- fluctuating pressure
- excessive vibration
- reduced cleaning performance
- irregular water flow
- noisy pump operation
- reduced pump efficiency
- accelerated valve wear
These symptoms should never be ignored.
Why Cavitation Causes Damage
As vapour bubbles collapse they generate extremely high localised forces.
Over time this causes:
- pitting inside the pump manifold
- damaged inlet valves
- worn valve seats
- cracked ceramic pistons
- damaged seals
- reduced pump efficiency
Continued operation accelerates wear throughout the pumping system.
Suction Feed vs Mains Feed
Cavitation is more likely to occur when operating from a suction feed.
Common suction-feed problems include:
- excessive lift height
- undersized suction hose
- air leaks
- blocked foot valves
- poor tank outlet design
Correct suction system design is essential to maintaining reliable pump operation.
Preventing Pump Cavitation
Professional operators should always:
- use the correct inlet hose diameter
- keep suction hoses as short as practical
- inspect inlet filters regularly
- eliminate air leaks
- ensure adequate water supply
- avoid excessive suction lift
- maintain clean water supplies
- check hoses for collapse or restriction
Correct installation is the best defence against cavitation.
Foreman System Configuration
Foreman professional pressure washers are designed to minimise cavitation risk through:
- correctly specified inlet hose sizes
- unrestricted water pathways
- professional-grade inlet filtration
- correctly matched pump flow rates
- calibrated nozzle selection
- engineered system layouts
Every Foreman machine is configured to promote reliable water flow and stable pump operation.
Common Warning Signs
Stop operating the machine immediately if you notice:
- loud knocking noises
- unstable operating pressure
- severe vibration
- sudden loss of performance
- pulsing water delivery
- overheating
- excessive pump noise
Early diagnosis often prevents costly repairs.
Operator Guidance
Always
- maintain adequate water supply
- clean inlet filters
- inspect hoses regularly
- use correctly sized inlet plumbing
- repair leaking suction fittings immediately
Never
- operate with blocked filters
- use collapsed hoses
- exceed recommended suction lift
- run with inadequate water supply
- ignore unusual pump noises
Frequently Asked Questions
What is pump cavitation?
Pump cavitation is the formation and collapse of vapour bubbles inside a pump caused by insufficient inlet water supply.
Can cavitation destroy a pressure washer pump?
Yes. Continued cavitation can rapidly damage valves, pistons, manifolds and seals.
Does suction feed cause cavitation?
Not by itself. A correctly designed suction system works well, but poor installation greatly increases cavitation risk.
How do I stop cavitation?
Ensure unrestricted water flow, clean inlet filtration, correctly sized hoses and eliminate all air leaks.
Related Technical Guides
- Why Do Pumps Fail?
- Suction Feed vs Mains Feed Systems
- Hose Size & Length Guide
- Return-to-Head vs Return-to-Tank Systems
- Pressure & Flow Rate Explained
Related Collections & Products
- Petrol Pressure Washers
- Diesel Pressure Washers
- WRX-HD Gearbox-Driven Range
- Pump Service Components
- Inlet Filters & Strainers
Technical Disclaimer
Foreman Technical Guides are intended to support professional equipment understanding and do not replace manufacturer instructions, operator training or official safety documentation.