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April 7, 1989

Chlorine, pH, and Control of Legionella in Hospital Plumbing Systems

JAMA. 1989;261(13):1882-1883. doi:10.1001/jama.1989.03420130044020

To the Editor. —  We wish to add a few comments to the excellent letter recently published in The Journal concerning control of Legionella in potable water.1 Mead et al showed that continuous hyperchlorination of plumbing systems, at chlorine levels as low as 0.5 mg/L or less, may be adequate to prevent colonization and replication of Legionella. Their finding is based on experience with a hospital system in which chlorine is being supplied at a concentration of 0.5 mg/L and in which, for corrosion control purposes, the water pH has been elevated from 6.7 to 8.8.It is not certain to us that control of Legionella can be achieved by low chlorine concentrations alone. In an earlier study, it was shown that natural strains of legionellae are substantially more resistant to chlorine than a number of other waterborne bacteria.2 Furthermore, legionellae obtained from a hyperchlorinated hospital plumbing system