Power Tools Explained
Pressure Washers and Air Compressors: A Beginner's Guide
How to choose a pressure washer (PSI/bar, flow rate, nozzles) and an air compressor (CFM, tank size, oil-free vs oiled), what each is good for and how to use them safely.
Pressure washers and air compressors both move fluid under pressure, and both turn hours of work into minutes. A pressure washer cleans patios, decks, cars and bikes. An air compressor inflates tyres, powers nail guns and air tools, and blows dust out of machinery. This guide explains the numbers so you can pick the right size.
Pressure washers
Quick answer
- Electric 100–140 bar (1,500–2,000 PSI) with 6–8 L/min flow suits cars, bikes, furniture and small patios.
- For large driveways and decks, 140–180 bar with higher flow, or rent a petrol unit.
- Flow rate matters as much as pressure: it is what carries dirt away.
Key specs
- Pressure (bar / PSI): cutting power. 1 bar ≈ 14.5 PSI.
- Flow (L/min or GPM): rinsing power. Higher flow cleans faster.
- Cleaning units: PSI × GPM, a useful comparison figure.
- Motor: induction motors are quieter and last longer than universal motors.
- Pump: metal pump heads last longer than plastic ones.
- Hose length and reel, and a detergent tank or foam cannon.
Nozzles
| Nozzle | Spray | Use |
|---|---|---|
| 0° (red) | Pinpoint | Rarely; can damage surfaces and cause injury |
| 15° (yellow) | Narrow | Stripping tough dirt on concrete |
| 25° (green) | Medium | General cleaning, decks, patios |
| 40° (white) | Wide | Cars, windows, delicate surfaces |
| Soap (black) | Low pressure | Applying detergent |
| Rotary / turbo | Spinning jet | Fast concrete cleaning |
Tips
- Start with the widest nozzle and a distance of 30–50 cm; move closer only if needed.
- On cars, avoid spraying directly at seals, badges and paint chips.
- Soft woods can be furred or gouged; use low pressure along the grain.
- Never point at people, animals, electrical outlets or the unit itself. High-pressure water can penetrate skin and cause serious injury.
- Drain and protect the pump from frost in winter.
Air compressors
Quick answer
- For tyres, balls and occasional blowing: a small portable compressor or cordless inflator.
- For brad/nail guns and light air tools: 6–25 L (2–6 gal) tank, oil-free.
- For impact wrenches, spray guns and sanders: 50 L+ tank and high air delivery (CFM / L/min).
Key specs
- Pressure (bar / PSI): most tools need 6–6.3 bar (90 PSI) at the tool. Compressors typically deliver 8–10 bar max.
- Air delivery (L/min or CFM): the volume of air per minute. This is the most important figure for air tools. Check "free air delivery" (FAD) rather than "air displacement", which is higher and less realistic.
- Tank size: a buffer. Bigger tanks run tools longer before the motor restarts.
- Oil-free vs oil-lubricated: oil-free is maintenance-free and lighter but louder and has a shorter life; oiled compressors are quieter and more durable.
- Noise: "silent" compressors (around 60–70 dB) are much nicer indoors.
Air consumption of common tools
| Tool | Typical air use |
|---|---|
| Tyre inflator, blow gun | Low, intermittent |
| Brad nailer, stapler | Low |
| 1/2" impact wrench | Medium–high (~110–170 L/min average, higher peak) |
| Spray gun (HVLP) | High, continuous |
| Air sander, die grinder | Very high, continuous |
Figures vary by tool; check the tool's specification and choose a compressor that delivers more than the tool needs.
Safety and maintenance
- Drain condensation from the tank regularly (daily with frequent use) to prevent rust.
- Never exceed the maximum pressure of hoses and tools; use a regulator.
- Never point compressed air at skin or use it to clean clothes on your body.
- Wear eye protection when blowing out dust.
For car tyres specifically, compare options in our tire inflator guide.
Frequently asked questions
Is a pressure washer safe for car paint?
Yes with a wide (40°) nozzle, moderate pressure and a distance of at least 30 cm. Avoid chipped paint, stickers and rubber seals.
What size compressor for an air impact wrench?
Usually 50 L or larger with good free air delivery. Small compressors will run out of air quickly. Many homeowners find a cordless impact wrench simpler.
This guide is general information, not professional advice. Always read your tool's manual, use the right protective equipment and follow local building and electrical codes. See our disclaimer.