Disinfecting and Water Temperature

Advice from Dr. Laundry
Q.

Does the disinfecting action of bleach deactivate in water above 77°F?

A.

This is a great question!  The bleach active in Clorox® Regular Bleach2 is sodium hypochlorite, and it does not “deactivate” in water above 77°F.  However, a higher water temperature does increase the rate that the bleach degrades into salt and water.   This break down is natural, and is part of what makes bleach so environmentally friendly.  It is also why bleach solutions for disinfecting need to be mixed freshly each day.  Keeping the solution away from sunlight will also slow the decomposition, and using a water source that doesn’t contain metals or high water hardness will also help.  Using room temperature water is OK, even if the incoming ambient water temperature is greater than 77°F.  It’s also important to follow the label instructions—in general disinfecting bleach solutions for hard, non-porous surfaces should be ¾ cup bleach per gallon of water.  The bleach solution needs to be applied to the surface for 5 minutes to be disinfected, and then rinsed and allowed to air dry.