Dangers of Thermal Shock and Scalding in Residential Settings
An additional method to reduce water use in showers is to turn off the water while lathering and shampooing. The method requires three steps: 1) turn on water to rinse body and hair; 2) turn off water while shampooing hair and washing body with soap and washcloth; and 3) resume water flow and rinse off all shampoo and soap. Some showerheads are equipped with a “lathering valve” that allows the user to control the flow. (See the illustration.) However, caution must be used in pre-1987 homes where no scald protection valve is installed behind the wall.
While such a lathering valve appears to enable the user to save water, not all homes can use the device. In some cases, it also might endanger that user and lead to thermal shock and/or scalding when the water flow is resumed.