 toilets toilets more than 45 of water use in the average american home occurs in the bathroom with nearly 27 being used by toilets fortunately your household can significantly curb its toilet water usage by regularly checking for and fixing leaks retrofitting older model toilets or installing a new toilet toilets 101 toilet water use can vary significantly older toilets can use 35 5 or even up to 7 gallons of water with every flush federal plumbing standards now specify that new toilets can only use up to 16 gallons per flush gpf and there are new high efficiency toilet models that use up to 128 gpf replacing an older model toilet with a new lowflow 16 gpf or high efficiency toilet 128 gpf can greatly affect your household s total water usage toilet consumption average flushes per day estimated gallons used per person per year 7 gpf 5 12775 5 gpf 5 9125 35 gpf 5 6388 16 gpf 5 2920 128 gpf new 5 2336 american water works association not sure about the how much water your toilet uses per flush oftentimes manufacturers stamp their toilet s water usage per flush on the inside of the tank or on the neck of the toilet bowl if you cannot find your toilet s water use stamp then determining its age is your key to its water use federal plumbing standards passed in 1992 required that toilets use no more than 16 gpf so if your toilet was installed prior to 1992 then it likely uses 357 gpf new high efficiency toilets hets  watersense  think energystar  only water has made choosing a high quality toilet simple with its labeling system to earn this label  toilets must meet rigorous criteria for performance and must use no more than 128 gpf only hets that complete the thirdparty certification process can earn the watersense label  indoor  