Half a croissant, on a plate, with a sign in front of it saying '50c'
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Still Kettle

For Hard Water Areas: heat air into a plastic bag, boil water, distil, pour. Clean out.
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This is a really badly thought-out idea, but sod it, here goes:

Problem: Hard-Water areas : limescale build up on the metal kettle element, horrible limescale residue in the resulting water.

Solution: (maybe).

1. Three separate chambers in the kettle:

Chamber one: heat up AIR (ok, this is where it all goes wrong I think...), which is fed into a plastic bag - which sticks into Chamber two.

Chamber two: You fill this water from the tap. The plastic bag sticks into this chamber - so you have a hot-air->water heat exchanger, this chamber is connected (via a condensing pipe) to chamber 3.

Chamber three: Collects the distilled water (I presume this is still boiling, or thereabouts - probably not, this also where it all goes wrong I think).

So you fill up chamber 2, boil the water in chamber 2 via chamber 1(the bag) and pour from chamber 3.

The water from chamber 3 will be free from limescale (I think) and still hot enough to make tea/coffee (I think).

Chamber 2 will still contain limescale - more concentrated than before, so will need to rinsed out. But (I think) because there is no metal element, it won't have anything to form on, and therefore can be simply washed/rinsed.

If the air->water heat exchanger is rubbish (I think Boyle/Pascal would have spotted a few problems perhaps...), then replace air-chamber with a sealed chamber containing oil or perhaps just pure-water.

Right, physicists...do your worst... :-)

monojohnny, Oct 23 2008

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       I suspect that if people would simply empty the kettle before it cooled, there wouldn't be nearly as much of a problem. Note that the following recommendations have not actually been tested.   

       Here's what typically happens though: Joe Plumber puts hard water in a new kettle, and heats it up. At this point even though some water has evaporated, no lime has precipitated onto the walls of the kettle because hot water can dissolve more lime than cold water. Once the water is hot, he pours half of it into teacups, and lets the other half sit. Even more water evaporates as it is sitting, so when it cools, there isn't as much water to hold the dissolved solids, so some precipitates out of the solution and sticks to the kettle. After the kettle is cool, the water gets dumped, and fresh hard water is added the next time he wants to make tea. When that water is heated, it will dissolve some of the existing deposits, hurting the taste of the tea, plus there is an even higher concentration of lime in the water, so when some of that water evaporates and cools, even more lime is left behind. Eventually enough lime builds up so that every batch of water is saturated with lime even when hot, and the lime on the kettle gets thinker and thicker.   

       If Joe would just dump all the water out of the kettle immediately after pouring the tea while it is still hot, very little lime would be left behind after each use, and what is left should be cleaned dissolved by the next batch so it shouldn't get worse. Joe shouldn't dump the extra water down the drain while it’s still hot because the lime would precipitate inside his drainpipes. Instead he should use a sacrificial pot where he can dump the water while it cools. After it cools and precipitates any excess lime, it can be safely poured down the drain. The sacrificial pot will get coated in lime deposits.   

       This solution is not as good as a pot that automatically distills the water since you will still have some lime in your tea that may affect the taste and get on your teacups (especially if you don’t finish drinking the tea while it is hot), but not as bad as before. If you want distilled water, I think it's cheaper to buy it at the grocery store than to make your own, but since you need the water to be hot anyway, it might be economical. Your mechanism for accomplishing this seem rather half-baked though [+].
scad mientist, Oct 23 2008
  

       well... I prefer the solution of having a "sacrificial"cast in a kettle you can open up... so after awhile you just open the kettle, take out a small limestone statue and put a new form in.
FlyingToaster, Oct 24 2008
  

       What [FlyingToaster] said (and what [monojohnny] hinted at). Having some sort of sacrificial/replacable liner seems like the best approach.
phoenix, Oct 24 2008
  

       Interesting..   

       //If Joe would just dump all the water out of the kettle immediately after pouring the tea while it is still hot,//   

       I actually do this already (down the drain though!! Must stop doing that !)...but still the lime grows (more slowly though)....   

       The lime appears to have an 'affinity' to the metal element - or is that just down to it being the place where the lime is mostly coming out of solution ? ....
monojohnny, Oct 24 2008
  

       [+] bunning it anyways; I think if you percolate heated air through the water you'll have a better surface area than a plain old metal element; still have to empty the lime out, but it won't be fused solid with anything.
FlyingToaster, Oct 24 2008
  

       Have more faith in yourself [monojohnny]. The idea works however there may be a more efficient way of doing it.   

       You are always going to get lime in the area of the kettle you are heating so it is probably easier to use an element rather than hot air. The air would have to be very hot and so pressure would end up being an issue.   

       To get the water from chamber 2 to 3 why not use the pressure created to force the water through a filter via reverse osmosis. This would remove the limescale from the wanted water and keep it seperate. The filter would need to be changed occasionally.
miasere, Oct 27 2008
  
      
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