What's added to big fountains that turns the water green?
October 12, 2009 7:44 PM   Subscribe

Why is the fountain blue? Here in Silicon Valley, two parks have Geneva-style fountains in the center of their lakes -- one in Sunnyvale, another in Cupertino. Instead of white, like in Switzerland, the water's a kind of azure turquoise. Why? A caustic acid to burn anyone foolish enough to take a dip? Chemicals to eradicate algae? Please advise.

I'm reminded of the water I noticed in Disneyland's Rivers of America -- you wouldn't want to fall in there because the water's not clear, rather an opaque green, I guessed to hide the workings of various underwater machinery.
posted by Rash to Technology (12 answers total) 1 user marked this as a favorite
Some cities add dye to their fountains either for their own mysterious aesthetic reasons, or to mark special occasions, like the blue fountains for cancer awareness in Pittsburgh.

I've seen "red, white and blue" fountains on a few Fourth of July weekends.
posted by rokusan at 7:55 PM on October 12, 2009

Are you sure it's the water and not the tile or painted plaster of the fountain itself? I've seen more than a few really nice blue-watered fixtures, but the water itself was just plain old clear.
posted by dnesan at 7:57 PM on October 12, 2009

A Geneva-style fountain is a single, high jet of water rising directly out of the center (image). The visible water's nowhere near any tile or painted plaster. And this tint isn't seasonal in Silicon Valley, but always present, throughout the year.
posted by Rash at 8:08 PM on October 12, 2009

My guess would be that ambient blue light from the sky is part of the answer.

Does it run at night? Is it lit at night? If yes and yes, does it look blue at night?
posted by Chocolate Pickle at 8:20 PM on October 12, 2009

The water is clearly dyed blue/green in Cupertino. I've often wondered why myself. :)
posted by gkostolny at 8:31 PM on October 12, 2009

Growing up in Florida, where all of the good mini-golf places had bright blue water, I was told that the dye was, indeed, an anti-scum measure. Searching for the right things on Google seems to confirm that there are anti-algae dyes out there.

Apparently it works by blocking the wavelengths of light photosynthesized by the algae.

I think it's supposed to be cheaper than chlorination, since chlorine tends to need a lot of maintenance.
posted by that girl at 8:58 PM on October 12, 2009

I can verify that the blue of the fountain in Sunnyvale is not natural; it looks like this. It is definitely not ambient blue light from the sky. I don't know why they do it, though. It looks bizarre.
posted by zsazsa at 9:06 PM on October 12, 2009

Copper sulfate is frequently added to ponds and fountains to kill stuff and it turns the water a weird color.
posted by jeb at 9:55 PM on October 12, 2009

They do it in Palo Alto, on California Ave, too. Not that this is a helpful answer! But clearly the peninsula towns are all talking to the same algae-control people.
posted by obliquicity at 9:59 PM on October 12, 2009

My old apartment complex in Pleasanton did this, too. So it's not restricted to the South Bay.
posted by phatkitten at 6:11 AM on October 13, 2009

I volunteer at a botanical garden, and they add dye to several of the park's fountains. I asked why, because it looks horribly fake and ruins the aesthetic appeal of a nice fountain. It turns out that they have had a big problem in the summer with parents letting their kids take a dip in the fountains, which is a big liability/sanitary risk for the park.

With the dye, they can tell parents "there are dangerous chemicals in there" or "that dye will stain clothing" and that takes care of the problem way more effectively than "no swimming" signs.
posted by jschu at 9:23 AM on October 13, 2009

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