I admit, I leave the shower running until the hot water kicks in before I step foot in the shower. It’s a bad habit and unfortunately a common one. millions of gallons worth of water is wasted on preheating showers or baths. Wasting water is a significant problem because the water that comes into our homes is treated, and treated water requires energy from factories to purify.
Some inventors have figured out a way to restrict the water-flow until a specified temperature has been achieved. This handy little device will cost you $45, however a much more economical solution is to just attach a simple switch above the shower-head to restrict the flow until ready to let it loose.