Rainwater and WAPA Water

St. John Virgin Islands Morning: Venus and the Moon
Venus & the Moon, Chocolate Hole, St. John 5:50 AM

I have two cisterns. If the first one runs out of water, I buy a truckload of water trucked to me from the WAPA desalination plant in Cruz Bay. The second cistern is left to collect rainwater and serves as a backup.

Access to the cisterns is provided by two, two-foot square concrete slabs covered with Mexican floor tile. They’re heavy and not easy to lift up. In order to check the water level without undue stress on the body, I drilled a small hole in each cover into which I could insert an aluminum rod. The rod would extend down to the bottom of the cistern and when retracted I would see how much of the rod was wet and thus have a good idea as to how much water was left in the cistern.

I usually don’t leave the rods in the cistern, preferring to store them in my pump room But this time I left both rods in place for an extended period of time. When I finally removed the rods to check levels, I found that one was clean and shiny and just like new and the other was pitted, corroded and discolored. Which rod do you think was which?

I would have guessed the clean one to be from the cistern containing the natural pure rainwater and the pitted one to come from the evil WAPA reverse osmosis plant.

But no, it was the other way around. It was mother nature’s rainwater that was corroding the aluminum bars. The bar in the cistern filled with WAPA water unchanged.

The explanation, I’m sorry to say, seems to be acid rain. Rainwater made acidic by exposure to pollutants spewed into the air from automobiles, power plants and factories.


Speaking of rain today’s forecast calls for a 70% chance of rain and to the south of us is a weather system called 98L with a coincidental 70% chance of development into a tropical cyclone by Sunday. Computer models have it moving our way.

“Strong thunderstorm activity continues in 98L today, despite strong wind shear to its north, around 30 knots. This wind shear is expected to decrease over the next few days, providing a window for the wave to develop over the weekend. Most of the models are expecting 98L to to strengthen to a tropical storm by Sunday. The GFS and the GFDL even go as far to say that 98L could reach Category 1 hurricane strength. In terms of track, all of the models are forecasting a recurving pattern. The ECMWF pushes the potential cyclone farthest west, possibly reaching Hispaniola. The HWRF carries the system northwest over the next three days, and across Puerto Rico. The GFS has a similar solution this morning, as well. The model with the eastern-most forecast is the GFDL, which expects 98L to track north-northwest, scraping the eastern side of the Lesser Antilles, and avoiding land thereafter.” Weather Underground

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4 thoughts on “Rainwater and WAPA Water”

  1. Bummer for sure on the acid rainwater. Hope your cisterns fill this weekend, even if with the acid rain.

    Will you be updating the Music Scene soon? It is appreciated and useful… thank you. TGIF!

  2. Do you know if any testing data of the water is available to compare the content of the WAPA vs “rainwater”?

  3. You might want to check pH – aluminum is one of the few common metals that are susceptible to alkaline corrosion. Water stored for a long time in concrete cisterns will beome alkaline by leaching out some of the minerals in the concrete. If you check the pH youmight find it to be in the 9 range (neutral is 7). The desal water probably flushes through your main system fast enough to not accumulate alkaline minerals.

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