Before 1994, most toilets used a whopping 3.5 gallons of water to flush. That's about 20 gallons per person each day. But if your toilet was made after '94, the year the federal government required that toilets use no more than 1.6 gallons per flush, you already have what's known as a low-flow toilet. You can save even more water by installing inexpensive toilet dams, which can easily be inserted in the back of your tank, and hold back about 1.3 gallons of water per flush. Of course, the most efficient toilets these days are dual-flush models, which offer a 1.6 gallons per flush mode and one that uses as little as .09. Recently, the Brondell
company started offering an easy-to-install retrofit device (about $100) that turns existing toilets into dual-flush models.