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Name: James P.
Status: other
Age: 60s
Location: N/A 
Country: N/A
Date: 11/15/2004


Question:
A question from Las Vegas, Nevada. The drought has put limits on water use, the first to be suppressed are water fountains and waterfalls. The development were I have a home, has stopped the waterfall, actually creating an eyesore. My idea and question is,"what if we used a fluid, not susceptible to the evaporation from the desert heat, recirculating that fluid for the 'waterfall'??" I started with a combination with water, but now would be leaning to some oil if it is clear and water-like. Additionally we could coat the fake boulders with an clear epoxy to seal and enhance the look. Any thoughts? I am an engineer with the Army Corps of Engineers, these past 41 years.


Replies:
Thoughts, maybe. A little skepticism that you can pull it off OK. Maybe if completely cordoned off and carefully kept in the tub. Just burbling and sheeting, no spray. And your neighborhood would have to be unusually experiment-oriented.

There is no inorganic substitute. Phosphoric acid comes closest. It would be clear and very durable but not quite safe for the public. It is not nearly as acidic as the other well-known acids. If it has much water dissolved in it, the water can slowly evaporate. If it has little, it can steal some water back from the air. It slowly erodes rocks (i.e., your fountain), not so much because it is acidic, but because it is a low-melting oxide, and rocks are oxides, and like dissolves like. Phosphoric acid is good at suspending other oxides in its liquid. It makes little complexes around dissolved oxides, which themselves remain liquid.

So you want an oil.

It should boil at around 200C, so it is not an immediate flammability hazard. Drug-store Mineral Oil is that kind of thing, and it is very clear and initially non-toxic.

Having higher viscosity and index of refraction than water, it might actually look prettier.

It will not attack epoxies very fast at all, but it might make some of them stay rather soft, or detach from rocks. It is probably expensive to fill a fountain with. The sun's UV and ozone may use up its anti-oxidant in a while, then it will rapidly yellow.

You would want to investigate anti-oxidants to add periodically, and diagnostic methods, and reclamation services. It will never evaporate, so whatever splashes around will stay until removed with isopropanol or repeated soap or oil absorbent. You know that it will make concrete look wetter, darker. It might try to creep over the wall of the pool or through cracks, then what? If passersby look closely or touch, what will you tell them about getting it out of their clothes? Prepare to turn off the fountain automatically if the wind blows. Oil is less familiar than water, so legally you might not be liable for kids drinking slimy green water, but unforgiven if they drink yellow oil and have a little diarrhea or headaches. Despite all this it is the most conservative choice at this time.

You might want to learn about PEG's (poly-ethylene glycols), and about glycerine itself. I am not recommending them, but I think they are less yellowing. They might be the right thing to re-wet your epoxy with, periodically or constantly. Get expert advice about their toxicity and degradation products. They will attack epoxy and other plastics faster than pure mineral oil.

Extending that to an extreme, what if your fountain was 60% sugar/40% water. Maybe the evaporation of water would be slower. Sugar-water that dense sure attracts insects, but not much can grow in it. Deposits wash away in water.

Perfluorocarbon oils are the thing that was supposed to make your idea possible. But despite the era they are still too expensive, and we no longer trust their harmlessness as naively as we used to. In principle we might be able to make "breathable water" for hi-G vehicles out of this, someday. But when an inert molecule is somehow broken in one little spot, it becomes something un-removable if it attaches somewhere in the body. Actually quite toxic. Not sure how fast degraded products would form in sunlight. Not sure if that's the final answer on fluorocarbons.

Di-Methyl Silicones can be ordered with a choice of boiling points, too, and might be cheaper than fluorocarbons today. When they eventually degrade, as wet-spots on the pavement may eventually do from UV and ozone, They make foggy gel, then faint white crust, because they are degrading to poor silicon dioxide (fluffy glass). This may or may not be compatible with upkeep of your fountain. They will not yellow, they will get foggy and whitish. Whether they can be filtered, restored, I am not sure. Despite degrading to silicon dioxide, they can be flammable. Being high-boiling probably minimizes that. Silicones are probably not non-toxic enough for a drinking dog. Breathing mist splashed into the air might cause silicosis, usually a dust-exposure illness.

Oils, Silicones, and Fluorocarbons are water-repellent, insulating liquids. So they could, in principle, generate static electricity by motion through pumps, etc. Could cause occasional freaky incidents if not watched.

So there is a perspective, if not much hope.

Jim Swenson


Yes, it would certainly be worthwhile to look for substitutes to reduce evaporation of water in a desert. Oil is one choice to look into, but you need to keep several things in mind. It might be expensive to buy. It would need to be properly disposed of when finished. Leaks into the soil could not be tolerated. Birds and animals might die in it. Splashing would create an oil mist. Finally, it could catch on fire.

Bob Erck


There are several issues that would have to be addressed:

1. Compatibility with the materials of construction and the design specs of the pumps etc. (both chemical and mechanical).

2. Toxicity and/or corrosivity (if that's a word?) of vapor and mist of the water substitute.

3. Mold and mildew attack (possibly).

4. Cost.

5. Photochemical reactivity.

The two substitutes that come to mind that might meet these issues are propylene glycol and/or glycerin.

Glycerin is more viscous than propylene glycol, both have low vapor pressure, both are relatively non-toxic and non-corrosive. Whether either or a combination would work would have to be tested. Local zoning ordinances would have to be consulted prior to use. I would NOT recommend a hydrocarbon mineral oil. Hydrocarbon mist is known to be an inhalation toxicant because the lungs have no mechanism for eliminating the mist. I do not believe either is a particularly good nutrient for microbes. I would NOT recommend ethylene glycol (anti-freeze). It is rather toxic to mammals. It is a problem for pet owners because dogs and cats will drink it because it tastes sweet. Both are photochemically stable.

Vince Calder



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