What Are Shade Balls? (And What They're Really For)

A shade ball is a hollow plastic ball — typically high-density polyethylene (HDPE) — floated on the surface of a body of water so that, en masse, the balls block sunlight from reaching the water below. Poured onto a surface, the balls self-arrange into a dense floating layer that shades the water without any anchoring or mechanical structure.

What shade balls are really for

The popular image of shade balls is “stopping evaporation,” and they do cut evaporation significantly. But the original engineering purpose was usually blocking ultraviolet light to control sunlight-driven problems:

• Limiting UV-driven chemical reactions in drinking water, most notably the formation of bromate when bromide and chlorine are exposed to sunlight.
• Suppressing algae and cyanobacteria, which need light to grow.
• Reducing evaporation by removing most of the open water surface — a major secondary benefit, often cited around 85–90% reduction for a dense cover.

In other words, shade balls are a chemical-free, low-maintenance way to manage what sunlight does to open water.

Where the idea became famous

The concept entered the public eye through the Los Angeles Department of Water and Power, which deployed roughly 96 million balls on the LA Reservoir (the approach was first trialed at the Ivanhoe Reservoir in 2008). The primary driver there was preventing bromate formation, with UV/algae control and evaporation reduction as additional benefits.

Note: that LADWP project was supplied by XavierC, LLC — not AWTT. We reference it here as category background, the way the rest of the industry does. Armor Ball® is AWTT’s distinct, industrial-grade product.

From commodity shade balls to Armor Ball®

Basic shade balls are usually thin-walled and intended mainly to block light. Armor Ball® is the industrial-grade evolution: a thicker-walled, reinforced HDPE ball engineered to do far more than shade.

• 91% surface coverage with 10.9 lb/ft² buoyancy
• Chemical resistance across pH 2–13 and a −70°F to +160°F operating range
• R-2 insulation and up to 90% evaporation reduction
• 25+ year design life and a 10-year warranty

That durability is what lets the same simple idea work on aggressive industrial liquids — tailings, leachate, produced water, digester surfaces — not just clean reservoirs.

Learn more: How it works · Armor Ball® vs. shade balls · Armor Ball® specs