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Pressure Washer 101

1. Sizing Your Pressure Washer

Horsepower (HP)

The horsepower of a cleaner determines the maximum GPM and PSI of your cleaner. Example: A 4HP motor can produce 3 GPM at 2000 PSI or 4 GPM at 1400 PSI. You can lower the PSI of a washer by using a larger nozzle or a dual wand. You cannot increase a cleaner’s size. A 4 HP motor cannot produce over its given capacity.

Pressure per Square Inch (PSI)

When choosing a cleaner, find the PSI required to break the bond between the dirt and the item being cleaned. The enclosed chart may help, or contact your local dealer. His experience can aid you in choosing the correct model for your application.

Gallon per Minute (GPM)

Remember every cleaner from smallest to largest does basically the same job of cleaning. With GPM, you are talking time. The more GPM, the less time you are taking to clean. Purchase a model large enough for your cleaning requirements. Too large is better than too small. Too small means longer wash times, more downtime, more repairs and greater cost.

Cleaning Power Units (CPU)

Cleaning Power Units (CPU’s), size pressure cleaners, cleaning power units equal PSI time GPM. Example 2 GPM x 1600 PSI = 3200 CPU. The larger the CPU, the more powerful the cleaner. Compare cleaning capabilities of different models by their CPU. The more cleaning power units the faster you will clean.


2. Choosing Features


Gas engine driven models are best if you are moving from place to place to do your cleaning. Self-contained trailer models are available. If you are cleaning inside or in a wash bay, consider an electric model. They are quieter. Both stationary gas models and portable oil fired models are available.

Belt Drive vs. Direct Drive

Two sources of drive are available. With direct drive, the pump is coupled directly to the power source (gas engine or electric motor). Belt drive indicates a belt leading from the power source drives the pump.

Direct driven models are more compact and weigh less than their belt driven counterparts. They are more economical to purchase. Direct driven pumps are rotating at the same RPM’s as the power source. There is more heat build up, more vibration, and any lockup of the pump normally causes more damage.

Belt driven models are driven at lower RPM’s. This gives less vibration, lower heat build up and less damage to the unit if pump lockup occurs. Belt driven models are heavier and bulkier.

Hot vs. Cold

Heavy dirt and mud accumulations can be cleaned with cold water. The greater the PSI and GPM, the faster the dirt disappears. With oil and grease, hot water will do a faster and better job. 165˚ is where grease softens and starts to melt therefore hot water is required. Hot water aids in chemical applications and also sanitizes where bacteria is a problem.

Hot water units cost more but clean better and faster. Whitco’s coil is a spiral wound, cold water wrap coil. The 1/2” inside diameter coil aids in reducing problems with lime buildup while the spiral wound design cuts down problems with sooting. Our coil forms the combustion chamber of the unit. This means there are no chamber hot spots, less troublesome insulation, and less fuel usage as efficiency increases.


A multitude of accessories and chemicals are available to enhance your machine’s performance and customize your experience.

  • Hose reels
  • Wands, wand extensions
  • Temperature control kits
  • Revolving brushes
  • Rotating nozzles
  • Drain cleaning nozzles
  • Wet sand blasters
  • Surface cleaners
  • Nozzle packs (different spray angles)
  • Low pressure chemical applications


3. Important Safety Features

1. A relief valve at the inlet of the coil

2. Safety switch cuts power to the burner if insufficient water flow occurs

3. Trigger gun protects operator

4. Safety glasses on the operator

5. Temperature control

6. Time delay shut downs (optional)

4. Where to Buy

Buy from your local dealer. This gives you local service and knowledge. Buy cleaners made in America as parts are readily available and Whitco provides a variety of machines: oil fired electric, gas fired electric, gas engine drive, diesel drive, hot or cold. Be certain to buy a cleaner that works efficiently for your job and buy local for service and parts.