| Good idea Mike. That will work.
The only problem with using activated carbon is that its often hard to tell when the stuff is used up. The carbon has chemical attachment sites on its surface and various stuff from the water becomes attached to the carbon and effectviely removed from the water. However, when all those attachment sites are used up, then it stops working and the carbon has to be replaced.
As you have said before, Hawaii's tap water is some of the best in the world. The amounts of things that would be absorbed by activated carbon are tiny to non-existent; at least until they decide to chlorinate it. Even without chlorine, the activated carbon would eventually be used up from trace amounts of this and that. Although they are not readily absorbed, carbon dioxide, non-chelated iron, alkalinity and such will eventually render the activated carbon useless. A chlorine slug would use it up more quickly. Trouble is, you have no way of knowing if any chlorine has come through the tap.
To be safe, you would want to replace the activated carbon every now and then. I have no idea what the replacement interval should be. The only way to find out would be to replace the charcoal after six months or so and test the old charcoal with a small, but measurable, amount of chlorine. Chlorine is easy to test for. If it disappears, you know that you removed the carbon too soon and may be able to wait longer next time.
For areas where the water is routinely chlorinated or there are certain other pollutants, activated carbon can become an expensive way to deal with the situatin as it must be replaced fairly frequently. There are many grades of activated carbon. The best and most expensive ones have been acid washed so the ash does not raise the pH, and it releases very little phosphate. The cheapest ones release a lot of phosphate.
-steve |