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Ask Dr. Laundry

Ask Dr. Laundry

Proper Water Temperature for Disinfecting

By Dr. Laundry April 27, 2011

Q: I work for an ambulatory care center and we currently do our own laundry. Our hot water cannot reach 160°F but we use the hottest water possible, and add bleach to all loads. During a recent survey we were told that depending on the temperature of the water, different quantities of bleach are required. Currently, manufacture label directions are followed. I did not find any language to the effect of water temperature and required concentration of bleach in CDC or other guidelines, and I was wondering if you happen to have any information about this.

A: This is such an interesting question because there are so many different parameters your care facility must manage to provide a safe environment for your patients. I reviewed an on-line copy of the CDC guidelines at http://www.cdc.gov/hicpac/pdf/guidelines/eic_in_HCF_03.pdf to understand the background of your question. There are two Clorox EPA registered disinfectants, Clorox® Regular-Bleach1 and Clorox ® Germicidal Bleach1. Their disinfectant use is governed by whether or not the product has had efficacy for specific organisms established under specific use conditions.

When adding bleach it is important to follow label instructions, however you have correctly noted that the label instructions do not mention adjusting bleach amounts based on specific water temperatures. That is something not pursued as part of our EPA registration, which identifies the amount of bleach to add regardless of the wash temperature (cold, warm, hot, etc.). As long as label instructions are followed, you can be confident that the laundry is safely and effectively disinfected regardless of the water temperature. Instructions are as follows:

• For Clorox® Regular-Bleach1, add 3/4 cup bleach per load for a standard washer. For a large washer or heavily soiled laundry, add up to 1¼ cups bleach.
• For Clorox® Germicidal Bleach1, add 1 cup per load for a standard washer. For a large washer or heavily soiled laundry, add up to 1¼ cups bleach.

CDC guidelines clarify that the use of an EPA-registered product is necessary for disinfectancy in low temperatures. It states “choose chemicals suitable for low-temperature washing at proper use concentration if low-temperature (<160°F [<70°C ]) laundry cycles are used (365–370). Category II” where “suitable” denotes an EPA-registered product. I do not think the intent of the report is to have facilities like yours adjust bleach usage for a precise temperature rather to clarify that only at temperatures of 160°F or higher, washing with detergent alone, is acceptable for eliminating bacteria.