If it’s not happened to you, you’ve probably seen it happen – an unsuspecting person in the shower screams as the shower water suddenly turns cold after someone flushes the toilet.

While it is an unpleasant surprise for the person in the shower, Ruben Delgado, owner of highly rated R&D Plumbing in Venice, Calif., says the problem can be traced to old shower valves and inadequate piping.

“If the piping is done properly, that wouldn’t happen,” he says.

Todd Marsh, owner of highly rated TRM Plumbing, Inc. in Los Angeles, says a pressure balancing valve would help compensate for these issues.

“What that does, it balances the pressure, hot and cold, so if you’re in the shower and somebody flushes the toilet, the valve itself adjusts so it doesn’t fluctuate,” Delgado explains.

Delgado says pressure balancing valves have been mandatory in California since 2005, and they must be installed in newly constructed homes and included in current bathroom remodels.