Pressure Washing Guide: Cost, PSI Settings & What You Can Clean

PSI (pounds per square inch): The measure of water pressure. Higher PSI = more cleaning power but also more potential for damage. Choosing the right PSI for each surface is critical. Too much pressure damages surfaces; too little doesn't clean effectively.

GPM (gallons per minute): The volume of water flow. Higher GPM = more rinse power and faster cleaning. PSI provides the cleaning force; GPM provides the rinsing efficiency. Cleaning power is calculated as PSI x GPM = cleaning units (CU). A 3,000 PSI / 2.5 GPM machine has 7,500 CU (good for most residential work).

Pressure washing vs power washing: Pressure washing uses cold or room-temperature water at high pressure. Power washing uses heated water at high pressure. Heated water is more effective on grease, oil, and stubborn stains. For most residential cleaning, pressure washing (cold water) is sufficient.

Nozzle tips: 0° (red): pinpoint blast. Extremely concentrated. Used for very stubborn spots only. Can damage most surfaces. Rarely used for residential cleaning. 15° (yellow): narrow fan. Aggressive cleaning. Good for concrete and hard surfaces. Can damage wood and siding if too close. 25° (green): medium fan. The most versatile nozzle for residential use. Good for: siding, fences, decks, and general cleaning. 40° (white): wide fan. Gentle rinsing. Good for: windows, delicate surfaces, and rinsing detergent. 65° (black/soap): widest fan with low pressure. Used for applying detergent. Always apply soap with this nozzle (low pressure lets the soap dwell on the surface).

Concrete (driveways, sidewalks, patios): PSI: 2,500-3,500. Nozzle: 15° or 25°. Tips: use a surface cleaner attachment for even results on large flat areas. Work in overlapping passes. Pre-treat stubborn stains (oil, rust) with appropriate cleaner. Sealed or stamped concrete: use lower PSI (2,000-2,500) to avoid removing the sealer.

Wood (decks, fences): PSI: 1,200-1,800 (softwood: pine, cedar), 1,500-2,200 (hardwood: ipe, mahogany). Nozzle: 25° or 40°. Tips: keep the nozzle 12-18 inches from the surface. Work WITH the grain (never across it). Too much pressure raises the wood grain (fuzzy surface) or gouges the wood. Use a wood cleaner or brightener for best results.

Vinyl siding: PSI: 1,300-1,600. Nozzle: 25° or 40°. Tips: spray at a downward or horizontal angle (never spray upward under the siding — water gets behind the siding and can cause damage). Start from the bottom and work up (prevents streaking). Rinse from top down. Use a siding-specific detergent for mold, mildew, and algae.

Brick and masonry: PSI: 1,500-2,500. Nozzle: 25°. Tips: avoid high pressure on old or deteriorated mortar joints (can blast out the mortar). Use a masonry cleaner for efflorescence (white salt deposits). Soft-washing (low pressure + chemical treatment) is often better for brick than high-pressure blasting.

Vehicles: PSI: 1,200-1,500. Nozzle: 25° or 40°. Tips: use a car-wash detergent. Keep the nozzle 3+ feet from the surface. Avoid the 0° and 15° nozzles (will damage paint). Don't pressure wash convertible tops, vinyl wraps, or damaged paint.

Roof (soft wash only): PSI: 500-1,000 (very low). Method: soft washing (low pressure + chemical treatment). Never use high pressure on a roof (damages shingles, removes granules). Apply a roof cleaning solution (sodium hypochlorite + surfactant) at low pressure. Let the solution kill algae, moss, and lichen. Rinse gently or let rain wash it away. Many pros recommend hiring a professional for roof cleaning.

Professional pressure washing: House washing (siding): $200-$600 (1,500-2,500 sq ft home). Driveway: $100-$300 (2-car driveway). Deck: $100-$350 (200-500 sq ft). Fence: $100-$300 (100-200 linear feet). Patio: $75-$200. Roof (soft wash): $250-$600. Full exterior package (house + driveway + patio + walkways): $400-$1,000. Pricing is typically by square foot ($0.08-$0.35/sq ft) or by the job.

Equipment cost (buying your own): Electric pressure washer (1,300-2,300 PSI): $100-$300. Good for: cars, patio furniture, small decks, siding touch-ups. Light-duty residential use. Gas pressure washer (2,500-3,500 PSI): $250-$600. Good for: driveways, large decks, fences, whole-house siding. The workhorse for homeowner use. Commercial gas (3,500-4,500+ PSI): $800-$2,000+. For professional use. Surface cleaner attachment: $50-$150 (essential for driveways and patios — provides even cleaning without zebra stripes). Extension wand (for reaching high areas): $30-$80. Hose extensions: $20-$50.

Renting: Pressure washer rental (gas, 3,000+ PSI): $50-$100/day from Home Depot, Lowes, or equipment rental stores. Good option for occasional use (1-2 times per year).

Never pressure wash: Old brick with deteriorated mortar (blasts out the mortar). Painted surfaces you want to keep (can peel paint). Lead-painted surfaces (creates hazardous lead dust and contaminated water — regulated by EPA). Windows (high pressure can crack glass and force water past seals). Old wood with rot (pressure makes damage worse). Roof shingles with high pressure (strips granules, shortens roof life — use soft wash only). Electrical panels, outlets, and fixtures. Air conditioning units (use a garden hose instead). Plants and shrubs at close range (the force damages them). Stained or sealed concrete that you want to keep sealed (can strip the sealer). People, pets, or animals (pressure washers cause serious injury).

Safety: Never point the nozzle at anyone (high-pressure water can cause serious injury including lacerations and injection injuries). Wear eye protection. Wear closed-toe shoes (no sandals). Be aware of electrical hazards (outdoor outlets, power lines). Don't use a gas pressure washer in an enclosed space (carbon monoxide risk). Use ear protection with gas pressure washers. Be careful on ladders (the kickback from the wand can throw you off balance). Test in an inconspicuous area first (especially on wood, siding, and painted surfaces).

Cleaning process: Step 1: Apply detergent. Use the black (65°/soap) nozzle. Apply from bottom to top (prevents streaking). Let the detergent dwell for 5-10 minutes (don't let it dry). Step 2: Switch to the appropriate cleaning nozzle (25° for most surfaces). Step 3: Rinse from top to bottom. Step 4: Work in sections (don't let soap dry on the surface).

Detergents: House wash (siding, fences): sodium hypochlorite (bleach-based) for algae, mold, and mildew. Simple Green or equivalent for general dirt. Concrete: concrete-specific degreaser for oil stains. Sodium hydroxide (lye-based) for heavy buildup. Wood: wood cleaner (sodium percarbonate — oxygen bleach). Followed by a wood brightener (oxalic acid) to restore natural color.

Common mistakes: Using too much pressure (start low, increase as needed). Getting too close to the surface (maintain 12-18 inches for most surfaces). Spraying upward under siding (drives water behind the siding). Not using detergent (water alone doesn't remove mold, mildew, or algae effectively). Leaving pressure lines on the surface (keep the wand moving, overlap passes evenly). Not protecting plants (cover or wet plants before cleaning nearby — detergent can damage them).