Commercial Pressure Washer

Discussion in 'Builders' Talk' started by dave andy, Sep 15, 2020 at 1:06 AM.

  1. dave andy

    dave andy Member

    A friend had a petrol pressure washer and the psi was something silly. What gives these commercial units far more power than my Karcher?
  2. Joe the Plumber

    Joe the Plumber Screwfix Select

    Obviously I don't know the specific machines, but often, a decent pressure washer has a higher flow rate rather than higher pressure compared to
    a cheaper unit.

    My own Kranzle electric pressure washer is 150PSI, but compared to its predecessor, a Halfords one of the same pressure, it is much more powerful,
    and that's down to litres per minute, not PSI.
  3. Bob Rathbone

    Bob Rathbone Screwfix Select

    Karcher make a point of the low water usage in their adverts. The ability to remove dirt is all down to the energy in the water jet (e=mc2) as Einstein found. As the pressure is limited by pump design, most washers use a 3 piston squash plate pump, the only variable will be the water volume. The petrol powered washer is not limited to the electrical power available at a socket outlet, but the size of the petrol engine, which can be any size.
  4. quasar9

    quasar9 Active Member

    Bob is correct in his answer but it’s more like F=Ma, where force or kinetic energy in this case, is M, mass of water multiplied by a, acceleration. :D. So both volume of water and it’s speed at exit from the nozzle are important.
  5. dave andy

    dave andy Member

    Ok that makes sense. How do you increase flow? Are they been fed from a garden hose still?
  6. Frutbunn

    Frutbunn Active Member

    I rebuilt my mates old Honda engined washer, can't remember the manufacturer name of the pump but if I remember correctly they were Danish, had to wait a week for some of the non standard seals.
    Brilliant bit of kit, way better than any of the electric ones I've used though this one had the ubiquitous Honda GX160 engine four stroke, so loads of power. Engine was years old, only needed a new crank cos someone had continued to use it when the pump had rattled loose of the end of the crank and knackered the crank taper end. Engine was like new otherwise.
    Well worth spending £150 (free labour) on it than some new Chinese ****.
  7. quasar9

    quasar9 Active Member

    You can’t, hence they try to increase pressure so nozzle velocity goes up too. One solution is a tank, but you will only get short bursts, the time dependent on its volume.
  8. dave andy

    dave andy Member

    So how do they work when I see chaps cleaning drives with a large jetwash in the back of the van. How do they get an increased flow?
  9. quasar9

    quasar9 Active Member

    they usually have a large plastic tank, which they fill between jobs. Usually gives them around 30 minutes. I have seen zip car service vans clean the alloys and then wash the body sparingly with a bucket.
  10. dave andy

    dave andy Member

    But does this tank allow them to increase flow?
  11. quasar9

    quasar9 Active Member

    Yes, as you can have as wide a pipe as the pump can handle, where as most domestic models are limited by a garden hose around 15mm in diameter but does have the benefit of arriving at some pressure where as the tank pressure is based on the volume of water above the outlet
    Joshuaojs likes this.
  12. hippy mickey

    hippy mickey New Member

    Domestic karcher k2
    Brand Karcher
    Cable length 5m
    Connection size 19.05mm
    Hose length 4m
    Maximum flow rate 360L/hr
    Maximum operating pressure 110bar
    Maximum operating temperature 40°C
    Power output 1.4kW
    Power voltage supply 240V

    Commercial washer
    Model: 30KLN+ES
    Max Pressure:
    207 Bar / 3000 PSI

    3.3 GPM / 15 LPM

    Heavy Duty Triple Piston Cat Pump

    Yanmar L100N Diesel Push Button Electric Start with recoil backup

    Triple V-Belt Drive Ensures long life on Engine/Pump

    Suction or Direct Feed

    Suction Hose:
    4.5m 3/4" Quality Suction Hose, with Brendon SS Suction Strainer

    Delivery Hose:
    15m 3/8" Double Braided Delivery Hose & Cplgs

    Weight & Dimensions:
    147kg 1050mm x 680mm x 800mm

    the pump and motor are what counts as you can see from above Commercial unit way more powerful and costly Than domestic karcher. And will also do a lot more damage to things very easily. If you have low water pressure ( or commercial unit) you need a water tank eg household wheelie bin if your washer has a draw pipe fill up bin drop pipe in away you go check bin size for ltr holding and then washer ltr per minute use, that’s how long you can wash for don’t turn the hose off will increase wash time.

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