At 09:21 PM 6/17/2008, you wrote:
>Hi Folks,
>
>I have finally installed a rain water tank.  I now fill my 19 litre
>water cooler bottle from a small tap that I have piped into the house
>at floor level.
>
>Its a pain to fill as it is slow and the tap under the sink is awkward
>to get to.
>
>What I would like to do is sense the level in the cooler resevoir and
>use a pump to top it up as it is used.
>
>The tank and cooler hieghts require that I pump and shut off the flow
>as the level in the water tank can be above or below the level of the
>cooler.
>
>I want to minimise on standby current, minimise on price and come up
>with an elegant solution.  Naturally.
>
>I have come up with 3 solutions.
>
>1. Using a small easily available cheap windscreen washer pump, pump
>the water up thru a loop of water pipe that extends above the top of
>the water tank and then flows down thru pipe to the water cooler.  At
>the apex of the water pipe loop at a point above the water tank
>install something like a shephards crook so there is an opening to
>air.
>
>This will allow the water to be pumped up under pump pressure then
>flow down to the cooler under gravity.  Once the pump is shut off the
>water remaining on the tank side of the loop will return to the tank
>and on the water cooler side will empty into the water cooler.  ie
>there will be no syphon action as there will be an opening at the apex
>of the loop.
>
>I like this solution but is a little untidy plumbing wise and results
>in more pipe exposed to the sun and I dont think it is good to have
>rainwater at raised temperatures.
>
>2. Use a sqeeze pump (do they use another name for these) like the
>ones used to deliver accurate doses for medical purposes.

"Peristaltic pump"

>  For me this
>is difficult to build or aquire.  I like this as it provides a method
>that combines pumping and shutting of the flow in one device.
>
>3. Use a windscreen washer pump and a solenoid.  This is not a bad
>idea but I cant seem to find small solenoid valves and havent
>experimented (as I have none) to see if they significantly restrict
>flow.  Most of these that I can source are desgned for irrigation and
>as such the pressure they control would be quite high compared with
>what a windscreen pump can deliver and not sure if they would work at
>all.
>
>Anyone have any clever solutions or know a good source of low pressure
>smallish solenoid valves (in Perth Western Australia).

I don't think appliance solenoid valves will work-- AFAIUI they're generally
pilot valves which depend on high pressure to operate.

>I think I have the control side of things sorted.  I considered reed
>switch with floating magnet but I have decided to just use a probe
>that detects the level of water by the drop in resistance.
>
>Thanks for your time.  Any help greatly appreciated.
>
>Cheers Justin
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