> All of the pieces have come together very nicely except one. I am 
> having
> trouble finding a water pump that:
>
> 1: Can move moderate volumes,
>
> 2: At very low head,
>
> 3: Quietly,
>
> 4: Cheaply,
>
> 5: and is safe for potable water (drinking water if any non-English 
> speakers
> don't know the word)

1. Any number of small fountain pumps fill the bill (and the Peltier 
chamber ;-) ).
Most use magnetically coupled rotors with all surfaces in plastic. 
Potentially highly suitable for drinking water. Specific 
implementations may make a given unit not so so check carefully.

2.    Peristaltic pump.

3. You could try "my" 'Pistonless Piston Pump. I invented this as a 
rocket propellant pump some years ago and only subsequently found out 
that Lockheed Martin had patented the idea about 4 years before that. 
A version of this was independently invented by and being developed in 
secret by Flometrics (see it at 
http://www.flometrics.com/rockets/rocket_pump/rocketpump.htm) when I 
caused them some consternation by publishing my design. They now have 
numerous patents on various aspects. An idea which I have public 
domained and which is *NOT* covered by the LM patent is to use a 
single chamber pump. The LM patent is based on 3 or more chambers with 
2 being mentioned as a throw away at the very end. 2 chambers is fine. 
If you wish, you can use 2 or more of public domain single chamber 
pumps with a common controller running them in appropriate phase 
relationship, when they look suspiciously like the patented version. 
It so happens that one of the very first British patents (1750s?) was 
for a mine pump that worked on the same principle - there is little 
new under the sun.

BUT - at the basic level, it goes like this.
Seal chamber.
Blow in air.
Water is expelled to Peltier cell.
Turn off air.
Open valve to chamber.
Let water drain back in from Peltier cell.
Not exactly a stunning concept - but some day rockets will go to orbit 
on that principle. It has advantages over all current methods (and 
disadvantages).


A non return valve or 2 is needed - see Flometrics site to see how 
it's done.
Water is touched only by air.
If air supply is potable quality them water is too.


        RM

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