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Any advantage to smaller machine?

Discussion in 'Power Washing' started by John_99_2007, May 27, 2010.

  1. John_99_2007

    John_99_2007 LawnSite Member
    Posts: 127

    Mike- thanks for the info earlier.....another question:

    Comparing 5.5 gallon to 8 gallon pressure pro machines,
    is there ever an advantage to the SMALLER unit?

    Obviously, it's cheaper, less gas, but is it ever better operationally?

    For example, is it better have less flow if a small surface cleaner is needed in tight spots, or can the 8 gallon machine do everything with the correct nozzles and adjustments?

  2. PierreCiCi

    PierreCiCi LawnSite Member
    Posts: 34

    Do you understand how cleaning units are calculated with pressure-washers? Pressure X GPM. You will be much happier with the larger gpm machine. I currently have a 7.5gpm unit and a 14gpm unit. I use the 14gpm exclusively for surface cleaning. When you have finished surface cleaning and need to rinse down, you will definitely be glad you have more gpm.

    FCPWLLC LawnSite Senior Member
    Posts: 352

    Indoor cleaning is the only time I wished I was using less water.
  4. PierreCiCi

    PierreCiCi LawnSite Member
    Posts: 34

    That is true.
  5. John_99_2007

    John_99_2007 LawnSite Member
    Posts: 127

    So Pierre-

    After acting like I don't understand what I'm talking about, Michael gives a great example that may help me, to which you reply is true.

    Don't you feel silly now?
  6. PierreCiCi

    PierreCiCi LawnSite Member
    Posts: 34

    If I implied that you didn't know what you were talking about, it wasn't my intentions.
  7. Pumptecguy

    Pumptecguy Inactive
    Posts: 71


    I quick guide to help you decide what works for you. The correct combination of gpm and psi will provide the cleaning you want based upon your application.

    The 'perfect' combination of gpm and psi is 1 gpm per 300-400 psi. At this ratio, the water droplet mass is optimal for the velocity (sort of psi). Other examples are 1 gpm at 1000 psi with droplets sizes (masses) so small that they are like ping-pong balls fired from cannons, or 1 gpm at 50 psi with droplets like that of watermelons dropped on the surface. A good real world example of this perfect ratio is self-serve car wash (3.5 to 4 gpm at 1000-1200 psi). These systems are optimized to clean or no one will spend more quarters.

    More water will offer more flushing action for excessively dirty surfaces, however. I caution everyone against the 4 at 4000 type of pressure unless you know what you are doing. 700 psi to pierce the skin, 1000 psi to sever most hydraulic cables and splinter most wood decks.

    The perfect ratio washer will provide the most consistent cleaning and will be less prone to errors. For example, a 4 at 1500 pressure washer will provide a blade of water that has similar impact energy over a longer distance than a 4 at 4000. Conceptually, the 4 at 4000 washer loses so much energy so fast because of the smaller water droplet sizes that the sweet spot distance for cleaning versus non-cleaning or surface damage is rather small. In contrast, the 4 at 1500 washer will have a larger range of similar cleaning power because of the water droplet sizes will posses greater inertia.

    I hope this helps you and will ultimately save you money.

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