A Boat Tour of a Reservoir Filled With 96 Million Black Plastic Balls That Keep the Water Safe for Consumption

Veritasium host Derek Muller took a boat tour of a reservoir in Los Angeles that was filled with 96 million black balls made from HDPE recyclable, food-grade plastic. These balls, known as “Shade Balls” help reduce evaporation, but their main function is to keep the water safe from a chemical reaction that causes harmless bromide to turn carcinogenic with sunlight, thus ensuring the water remains safe for human consumption.

I took a boat through 96 million black plastic balls on the Los Angeles reservoir to find out why they’re there. …The balls are made of high-density polyethylene (HDPE) which is less dense than water so they float on the surface of the reservoir even if they break apart. They are 10cm (4 inches) in diameter and contain about 210ml of water.

While doing research, Muller had a chance to speak with Marty Adams, the Chief Operations Officer of the Los Angeles Department of Water and Power (LADP). Adams explained how the city became aware of the problem, the different approaches that were taken to address the problem and why they finally settled on the shade balls.

So we made this unfortunate scientific discovery that actually was not part of any regulatory scheme and so here we are at the reservoir. We have a water source that’s got bromide in it but it’s harmless. We have chlorine, we have to have to disinfect the water, and we have sunlight because it’s open. The only choice we have is to remove sunlight. …Doctor Brian White did some research and he found the shade ball.