Pressure Washer Specifications: What Actually Matters
Pressure (bar / PSI): The force of the water jet. Higher pressure removes tougher dirt, but excess pressure damages surfaces like wood, render and vehicles.
Flow rate (litres per minute): Volume of water delivered. High flow rate with moderate pressure is often more effective than high pressure with low flow — the water volume carries debris away.
Cleaning units (bar × L/min): A useful combined measure. Compare cleaning units when comparing machines: a 130 bar / 8 L/min machine has 1,040 CU; a 150 bar / 6 L/min machine has 900 CU — the "lower pressure" machine actually cleans more effectively.
Electric vs Petrol Pressure Washer
Electric: Quiet, no fumes, low maintenance. Pressure range typically 80–180 bar. Requires mains power — limits where you can work. Best for home use, patios, vehicles, regular jobs near an outlet.
Petrol: High pressure (180–350 bar), high flow rate, no cable. Best for professional use, construction sites, agricultural equipment, locations far from power.
Pressure Guide by Task
| Task | Recommended Pressure | Notes |
|---|---|---|
| Car washing | 80–120 bar | Higher pressures remove paint if used too close |
| Patio/driveway cleaning | 120–160 bar | Surface cleaner attachment recommended |
| Concrete cleaning | 150–200 bar | With rotating nozzle for efficiency |
| Graffiti removal | 200–350 bar | May need combined with detergent |
| Agricultural/construction equipment | 200–350 bar | Petrol unit recommended |
Hot Water vs Cold Water Pressure Washers
Hot water pressure washers (up to 80–120°C) cut through grease, oil and biological matter faster than cold water at any pressure. For agricultural use (barns, animal equipment), food processing, vehicle workshops, and professional cleaning: hot water is worth the significant price premium. For home patios, drives and vehicles: cold water is entirely adequate.
FAQ
Do I need a pressure washer with a water tank if I have mains supply?
Only if your water supply can't keep up with the washer's flow rate (some petrol models use 15+ L/min — check against your tap flow rate). For most home electric washers (6–8 L/min), mains supply is plenty.