If the shower water in your bathroom or tub suddenly gets dangerously hot, you're not alone. My parents have the same problem in their 35-year-old house—someone turning on water in the kitchen or flushing a toilet downstairs changes the water temperature for someone taking a shower upstairs. Scalding water is dangerous, especially for young kids who can’t turn it off. Approximately 3,800 people are injured and 34 people die each year from excessively hot tap water, according to the Consumer Product Safety Commission.
Anti-scald valves have been required by code for years, but older homes may not have them. And putting them in an existing bathroom means tearing open the walls to access the plumbing pipes.
An easier fix is to replace the showerhead and the tub spout with fixtures that have a built-in scald protection valve. To install, simply unscrew the existing showerhead or tub spout, wrap pipe tape around the exposed threads, caulk around the opening for a tub spout, then attach the new fixture. When the water reaches an unsafe temperature, the fixture automatically cuts the water flow to a trickle. Flow resumes when the water cools. Codes may still require an anti-scald valve (not just an anti-scald fixture). Check with your local building inspector.
Look for the fixtures (starting at $25) in home centers. Two manufacturers are American Valve and American Standard.