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  • whats more important?

    cfm or water lift on 50 ft - 75 ft. hose length

  • #2
    Inches of lift VS CFM

    CFM stands for cubic feet per minute. Inches of water lift refer to: how high can your vacuum suck a 1" diameter column of water straight up. Both are equally important in carpet cleaning and drying carpet. When comparing equipment on what dries the carpet the fastest, just multiple the numbers together. For example if I am comparing one extractor that has 2, 2 stages of vacuum in series and another with the vacuum motors in parallel. The serials machine is rated at 90 cfm X 155" of vacuum = 13,950 vacuum units. The parallel unit is rated for 180 cfm X 87" of vacuum = 15,660 vacuum units. Most manufacture give unrealistic figures on equipment specs. For example the specs. are taken at the machine, not at the end of your 50 foot hose set. A 2" diameter vacuum hose can handle 200 cfm with ease, while 1 1/2" hose the vacuum is restricted (like sucking a thick milk shake through a tiny straw). So even if the parallel machine has a higher vacuum unit rating, at the end of 50 feet of 1 1/2" vacuum hose they may be the same. When it comes to some attachments, 200 cfm is preferred. This includes the Turboteck Air Duct Cleaning System and the Hydro X Wand . I hope this helps.

    The only thing that I think might be added is that parallel refers that each vacuum motor has a hose that then sucks directly out of the vacuum tank. This configuration can increase the CFM (cubic feet per minute) by up to 100%, but does not increase the inches of water lift at all. Series vacuum means that the exhaust of the first vacuum motor gets sucked into the intake of the second motor. This increased the inches of water lift by 50% over the first but does not increase the CFM at all. In the carpet cleaning business, when the lip of the carpet cleaning wand seals down on the carpet, how much CFM can travel under the lip of the carpet cleaning wand through the carpet fibers and get into the machine?? Because this figure would be low, most carpet cleaning companies prefer the series units while people using the equipment for air duct cleaning or using the HydroX wand or the FloodPro purchase the high CFM models.
    Last edited by Donald; June 4, 2009, 09:43 PM.


    • #3
      inches vs cfm

      in the case with a rotovac would cfm be better utilized . thanks for taking the time to reply to all this stuff. you have very good manner as to explaining.


      • #4
        CFM vs Inches of lift

        Higher CFM is better for the Rotovac. Rotovac wand uses a lot of water so you would want a machine with auto fill/dump or larger tanks.