Just how many gallons per flush does a 7-year-old, 1.6-gpf toilet actually flush?
Hint: It's not necessarily 1.6 gallons.
On average all the low-flow toilets put in service seven years ago used almost 2 gallons to flush - about 25 percent more water than they should. Furthermore, more than a quarter of the households studied had at least one 1.6-gpf toilet that routinely used more than 2.2 gpf. Combine these high flush volumes with frequent incidences of double-flushing and flapper leaks, and you've got another big problem just now getting noticed.