Water - Letters

Whole Earth,  Spring, 2002  

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Dear Editor,

In the recent issue of the WE there is an article about a $300 device for disinfecting drinking water with UV-radiation. The device is touted as a low-cost solution to the drinking water problems of the developing world.

I would like to point out to you Aftim Acra's report published by UNICEF in 1984 on his research on the solar disinfection of drinking water. (http://almashriq.hiof.no/water/) It is also worth noting that several international projects are now in the works on this method.

Solar disinfection of drinking water simply consists of putting a standard plastic clear water bottle filled with potentially infected tap or well water in the sun to be disinfected by radiation from the sky. Time of exposure varies from twenty minutes to several hours.

The resulting water is safe and cheap, especially considering that clear plastic bottles are often a source of pollution in developing countries.

Barre Ludvigsen
By email

Peter,

I must take issue with your comments about on-demand water heaters (Winter 2001). At the urging of magazines like Whole Earth and others, we had our home designed to use an AquaStar On Demand water heater for the bath, laundry, and kitchen.

In Latin America and Europe, building permit departments allow gas on-demand heaters to be in the same room as the faucet they are heating. In America, you can't have a gas on-demand water heater in your kitchen or bathroom. Consequently, the length of time between the demand and the response is much longer. It took at least three times as long to get hot water to the shower with the on-demand. The cold water still in the pipes has to flow out before the heated-up water arrives (contrary to what your article implies) and then it takes a while for the requested water to heat up, and all the while water is flowing down the drain!

If one is washing dishes with a gas on-demand water heater not in the same room, one cannot turn the water on and off while rinsing. You have to let it run the whole time. Otherwise you have to go through the whole request-and-heat-up cycle over and over This is an enormous waste of water and, quite likely, the fuel to heat it. I added an electric on-demand one under my kitchen sink to solve this problem, but it still took longer to deliver hot water than the traditional hot water heater half-way across the house! I have only so much water in my well and had to take the on-demand heaters out because I literally didn't have enough water or time to stand there and wait for hot water.

Frankly, my guess is that the on-demand system doesn't save much fuel because it doesn't store heated water in an insulated tank, and it uses a huge burner--much bigger than the burner in a regular water heater. To get my water use down to reasonable proportions, I had to go back to traditional-style water heaters. Perhaps on-demand could work in perfectly designed situations, but I wish we had not been misled by incomplete information from articles such as yours.

Peggy Randall
By email

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