The average operating rate of U.S. plants that make chlorine and caustic soda rose to 86 percent in July, the highest level in 11 months, a trade group said.

The industry’s average operating rate for plants that make the chemicals known as chlor-alkali climbed from 82 percent in June, The Chlorine Institute, based in Arlington, Virginia, said today in an e-mail. Plants on average ran at 83 percent in July last year and at 86 percent of capacity in August.

Chlorine is used to make vinyl products such as siding and polyvinyl chloride pipe. Caustic soda, produced in tandem with chlorine, is used to make pulp, paper and soap. Dow Chemical Co. (DOW) is the world’s largest maker of chlor-alkali, followed by Occidental Petroleum Corp. (OXY), Olin Corp. (OLN) and PPG Industries Inc. (PPG)

To contact the reporter on this story: Jack Kaskey in Houston at jkaskey@bloomberg.net

To contact the editor responsible for this story: Simon Casey at scasey4@bloomberg.net