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Scary Water Pump

Discussion in 'Electronic Design' started by N. Thornton, Sep 22, 2003.

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  1. N. Thornton

    N. Thornton Guest


    I thought I'd ask about this. Is it possible to use a conventional
    cylinder vacuum cleaner (old sausage dog type) to pump clean water?
    These cleaners work by passing the filterd air stream through the
    motor to cool it, so the water would go thru motor as well.

    For any unaware person reading this, don't do it as its clearly
    dangerous, my question is whether its _possible_?

    Regards, NT :)
  2. yes- best to try it out in the bath first. Throw in a few handfulls of salt
    before you get in to improve the efficiency.
  3. Ian Stirling

    Ian Stirling Guest

    I'd have to say no.
    At least certainly no unaltered.
    The rotor spins at some tens of thousands of RPM.
    Even if it could keep this speed when water got to it, it'd be destroyed
    by cavitation and general stress, as it's so lightly built.

    Run at a few percent power, I think you would get some pumping action.
    If pumping very clean/distilled water, the corrosion may not be that bad,
    and you may get a reasonable life (few days of pumping continuously) as
    contaminants will get washed away from the brushes rather than conducting
    Losses from "windage" due to the close gaps in the motor will be large.
  4. Definite no-no !
    Water and air have vastly different viscocity.
    Quite apart from the scary water/electricity aspects.
    What about a Vax type wet/dry vacuum where
    the water doesn't come in contact with the motor?
    When the water container gets full you could automatically
    empty it with a pressure switch/ electrical solenoid.
    There is also a simpler way to do auto emptying using the
    weight of water to trip a counterweighted flap.
  5. I don't know how effective it might be, but you might
    consider using the exhaust airflow to suck up the water.

    -->Airflow--> --> Air+Water -->
    -----------------/ /----------------
    / /
    / /

    I'll think I'll patent that, call it a carburettor maybe.
  6. Graham

    Graham Guest


    I have used one to pump air out of a barrel. Another pipe from the barrel
    can be used to suck up water. You have to make sure that water level never
    reaches the air pipe, and you can only run it briefly as there isn't enough
    air going through the motor to cool it.

  7. Ian Stirling

    Ian Stirling Guest

    If you can live with slightly lower vacuum, then you put a hole in the tube
    from the barrel and allow cooling air in.
  8. Duncan Lees

    Duncan Lees Guest

    How about: /\ Vacuum
    | |
    | |
    | |
    ------------------------------------| |
    -->Airflow--> --> Air+Water |
    -----------------/ /----------------| |
    / / _| |_
    / / | | |
    / / | \/ | Water
    / / |~~~~~|
    / / |_____|

    Would that work, or would all the water still end up in the vac?

  9. Tony Bryer

    Tony Bryer Guest

    Older friends will remember the Flit flykiller sprays that worked
    just like this - far more ecological (from a material pov only) than
    aerosol cans. For a picture see

  10. No, how silly of you, you can't pump water thru a motor.

    But you can of course, pump gasoline.
    See your car's gas tank. Or Dave Barry.
  11. N. Thornton

    N. Thornton Guest


    Ian Stirling:
    You sure?
    Lets look at it this way. Water is more viscous, so as water flows
    thru it would presumably slow it down and work, at least in that

    Power consumption would go up from motor loading, but then water
    cooling would deal with that too, maybe.

    Of course there might be a fair bit of power flowing thru the water,
    so maybe it'd be warm water coming out the back.


    Right. I guess losses aren't too big a concern in something as barmy
    as this :)

    Anthony Wooldridge:
    You sure? Want me to try it and see? I'll bet you're wrong ;)
    actually that's not hard to deal with. earth the case and you have an
    earthed electrode heater.

    Regards, NT

    PS dont try this at home
  12. I have to admit that I'm an older reader and whilst I never saw one of those
    pump-type sprays in the flesh (well, metal: you know what I mean) we did
    have an attachment for our old Electrolux sausage type vacuum cleaner for
    spraying stuff (never sure what stuff: we had the gizmo but I never saw the
    instructions or any description for it). It consisted of a glass jar with a
    screw-on lid: the lid incorporated a telescopic tube which dipped into the
    jar, a socket for the vac hose and a nozzle out of which should emerge what
    was being sprayed. The idea was to attach the hose to the blow (exhaust) end
    of the vac so the flow of air through the gizmo would create a suction and
    draw up liquid from the bottle and spray it out as an aerosol.

    Never worked, mind.
  13. And trip the RCD which stops the pump.
    OK you could use an isolating transformer to stop that, (with extreme care)
    but when the seal between the motor and pump vanes leak (they are not
    designed for water)
    you get water in the motor electrics, electrolysis, and corrosion will
    eventually stop the motor
    if the huge increase in power caused by the presumably low conductivity tap
    or worse still dirty water doesn't.
    It could last a few minutes if you bypass the RCD. (MTBF 0.1 hrs my

    Much better to try the wet/dry Vax type with auto empty.
  14. NT, you've given us a bit of an underspecified problem - thus the ensuing

    When you say "possible," what do you mean? Do you mean "will it move any
    water at all," or do you mean "is this a reliable way to move water," or "is
    this a reliable and efficient way to move water," or ...? And, when you say
    "clean water," do you mean "clean and relatively ion-free water" or do you
    mean "water with no large suspended objects such as seaweed and/or rubber

    Of course you can pump clean water with a cylindrical vacuum cleaner, if you
    use it as a piston within some larger cylinder with appropriate valves. But
    I assume that's not what you mean.
  15. Interestingly, a choked off vacum cleaner draws much less power than a free
    running one ! If you block the pipe, you will hear that the motor runs
    *faster* - showing that the load is less.

    This is due to the characteristics of centrifugal pumps - you can look it up
    in an engineering encyclopedia or handbook - or I'll bet there is info on
    the web.

    Possibly, the choked off cleaner may overheat because the motor still
    consumes power and has almost zero airflow.

    At work we have a solder fume extractor rigged up from a barrel vac hooked
    up to a solder iron tip extractor. Very little air flows into the cleaner
    through the small diameter tip pipe, yet the cleaner runs for minutes and
    has never failed.

  16. I remember my Dad in the 1960s spraypainting with one of those vacum cleaner
    attachments. It really did work for him. You put your finger over an air
    hole to start spraying. I wonder if its still in the garage at Mum's place

  17. Ian Buckner

    Ian Buckner Guest

    You can pump gasoline, however make _very_ sure you don't get down to
    Many years ago one of our guys wanted to get the fumes out of a car
    gas (petrol)
    tank using a vaccuum cleaner before welding a leak. The brush sparking
    the fumes, he lost most of his beard and eyebrows. Took him years to
    live it down.

  18. a

    a Guest

    It should work too, isnt that how most airbrushes still work today (although
    maybe the air source isnt from a vacuum cleaner any more :)
  19. N. Thornton

    N. Thornton Guest


    The challenge is on!
    What RCD? Plenty of places don't have one. For this experiment its a
    location with no RCD, of any kind.


    lol, I dont think it would be extreme care trying anything like this

    ah no, you misunderstand, its worse than that. In cylinder vacs all
    the air pumped by the impellor goes straight thru the motor to cool
    it. Not around it, thru it. That's how they use such small high power
    motors. So if one is used for pumping, the water goes right thru the
    motor mechanics and electrics from minute one. :)


    We got a 500 watt motor on a 30A fuse, 240v ring main. There is the
    question of just how much power would flow thru the water, I don't
    know. I spose if we dip most of the mains lead in the water we could
    at least cool that too. After all its only 2A rated.

    Hehe, how much you want to bet? I say it can be done. And I'm wililng
    to post practical results.

    I simply mean is it possible - not is it reliable, safe and sensible,
    just possible. And not for 3 seconds, but possible to empty the whole
    1000 gallon tank. That's about 4.5 tonnes of rainwater. So I expect
    it'll need to run for more than 0.1 hours.

    A big tank of rain water sitting next to a house. So, barely clean, no
    ducks anyway. Certainly not ion free.

    Hehe. What I mean is by plugging it in the mains and sticking the
    nozzle in the water. The really stupid way.

    Well no-one's convinced me I can't do it yet :)

    In case anyone's tempted, NEVER try this dangerous idea at home. Its
    really stupid.

    Regards, NT
  20. Mark Zenier

    Mark Zenier Guest

    aspriator, FYI.

    Mark Zenier Washington State resident
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