Rongjian manufactures shade balls, the black HDPE balls that float on open water to block the sun. Made famous covering the Los Angeles reservoir, a layer of 100 mm balls shades the surface so sunlight cannot drive algae growth or light-triggered reactions in the water, while the cover also cuts evaporation. The balls are moulded from UV-stabilised, carbon-black HDPE so they hold up for years in the open.
A single ball is light, around 40 g, and floats high; for windy sites the balls can be partly filled with water to weigh them down and keep the cover in place. They self-arrange into a complete floating layer with almost no maintenance, and they are inert and safe on drinking water. We supply them for drinking-water reservoirs, wastewater and chemical tanks, ponds and pools, factory-direct with free samples.
Typical specifications for Rongjian shade balls, moulded from UV-stabilised black HDPE. The standard ball is 100 mm; other sizes and a water-ballasted option are available. Free samples are supplied, and coverage is worked out from your surface area.
| PROPERTY | VALUE |
|---|---|
| Material | 100% Virgin HDPE, UV-stabilised |
| Colour | Black (carbon black) |
| Shape | Round |
| Diameter | 100 mm (other sizes on request) |
| Weight | ~40 g (hollow); water-ballasted option |
| CAS No. | 9002-88-4 (polyethylene) |
| Function | Sunlight blocking, evaporation reduction, algae control |
| UV Resistance | Stabilised for years of outdoor use |
| Coverage | ~115–135 balls per m² |
| Application | Reservoirs, wastewater, chemical tanks, ponds, pools |
Shade balls cover any open water that needs the sun kept off it, from a city drinking-water reservoir to a chemical storage tank. The four duties below cover most of what buyers order them for.
We have produced shade balls since 2010, out of Jiangxi in China, and ship them to water utilities, industrial plants and landscapers around the world. The balls are moulded from UV-stabilised virgin HDPE so they last in the open, and we work out the coverage from your surface area so you order the right number.
We hold the standard ball and make other sizes and a water-ballasted version to order, with free samples on request. Standard supply runs from sample quantities up to bulk orders by the container, with the test report shipped against the order and a reply on quotes within a day.
The standard ball is a hundred millimetres across, the size that gives full cover at a sensible cost on a large reservoir or basin, and we make other sizes for smaller ponds, tanks and special jobs. A hollow ball floats high and ships light; where wind is a problem the ball is part-filled with water to weigh it down. We set the size and the fill to the water and the site rather than offer one ball for everything.
We send free samples so a buyer can check the ball before committing, and we work out the coverage so the order is right first time. From your surface dimensions we calculate how many balls a full cover takes and the way they pack, so you are not left to guess the quantity or short the job. It takes the risk out of a first order and means the cover that arrives actually fills the water.
We ship shade balls to over a hundred countries. The balls are light, so even a large cover bags up and ships without heavy freight, and they are packed to arrive clean and ready to tip onto the water. From a sample to a container of balls, the order is packed and documented for export.
We are a factory, not a trading company. Every product ships from our own production lines in Pingxiang. You deal with the people who actually make the product.
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Shade balls are black HDPE balls that float on open water as a cover. By shading the surface they block sunlight, which stops algae growing and stops the light-driven reactions that form unwanted compounds in drinking water, and the cover also cuts evaporation. They became well known covering a large city reservoir.
They cut evaporation simply by covering the water surface, so far less of it escapes to the sun and wind. A complete floating layer shades and seals most of the surface, holding much of the water that an open reservoir or tank would otherwise lose, especially through a hot, dry season.
Black is chosen on purpose. The balls are coloured with carbon black, which is the most UV-stable pigment, so the HDPE survives years of full sun without going brittle, and black blocks light completely. A white or clear ball would let light through and would break down far sooner in the sun.
It depends on the surface area, with roughly a hundred and fifteen to a hundred and thirty-five balls covering each square metre of water for the standard size. The simplest way to order is to give us the surface area, and we work out the number of balls and the packing for full coverage. Send the dimensions and we will size it.
Yes. The balls are made from inert, virgin HDPE, the same family of plastic used for food and water containers, so they do not leach into the water. This is why they are used on drinking-water reservoirs, where they block light and cut evaporation without affecting the water. A food-grade material can be supplied on request.
Yes. The same ball covers a drinking-water reservoir, an industrial wastewater or chemical tank, a pond or lake, and a swimming pool. On each it blocks light, holds down evaporation and shades the surface, and the UV-stable HDPE stands up to sun and to many chemicals. Tell us the surface and the liquid and we will confirm the fit.
We send free samples, and the minimum order depends on the size, with bulk orders shipping by the container. Lead time runs from stock for the standard ball to a couple of weeks for other sizes or a water-ballasted version. Send the size and the quantity and we will confirm both on the quote.
Shade balls are black HDPE balls that float on open water as a cover. They came to public attention when a large city covered its drinking-water reservoir with millions of them, but the idea is simple: a floating layer of balls shades the water, blocking sunlight to control algae and light-driven reactions, and cutting evaporation from the surface. They need no liner, frame or power, and they self-arrange into a complete cover.
Sunlight on open water does two unwanted things: it grows algae, and in chlorinated or ozonated drinking water it drives reactions that can form compounds such as bromate. A complete cover of shade balls blocks that light, so both problems are held in check without dosing chemicals. At the same time the cover shades and seals the surface, which cuts the evaporation an open reservoir or tank loses to sun and wind.
It seems backwards to use black in the sun, but black is the right choice. The balls are pigmented with carbon black, the most UV-stable additive for HDPE, so they survive years of direct sun without becoming brittle, and black blocks light completely. A pale or clear ball would let light through, defeating the purpose, and would degrade far sooner. The small amount of extra heat a black ball absorbs is outweighed by its life and its light-blocking.
Coverage is worked out from the surface area. For the standard 100 mm ball, a complete cover takes roughly a hundred and fifteen to a hundred and thirty-five balls per square metre, packed across the surface. A hollow ball floats high and is the lightest to ship; on an exposed, windy site the balls can be part-filled with water to weigh them down so the wind cannot push the cover to one side. We size the order from your dimensions.
The same ball serves several duties. On a drinking-water reservoir it controls light-driven reactions and algae and saves water; on an industrial wastewater or chemical tank it covers the surface and holds down evaporation, odour and vapour; and on a pond, lake or pool it keeps algae down and cuts evaporation. Because the HDPE is inert and UV-stable, it suits potable water and many chemicals alike.
The balls are moulded from virgin HDPE stabilised against UV, which is what lets them float in full sun for years rather than cracking. HDPE is inert and from the same plastic family used for food and water containers, so it is safe on drinking water, and a food-grade material can be supplied where it is specified. With no moving parts, a shade-ball cover lasts for many years with almost no maintenance.
Consistent moulding and a proper UV stabiliser are what give the balls their outdoor life. The balls are made from 100% virgin, UV-stabilised HDPE, with free samples on request, and we work out the coverage for your water. We supply from sample quantities up to bulk orders by the container, in the standard size and to custom sizes.
