1.28 GPF Toilet vs 1.6 GPF Toilet
Part of our Toilets & Bidets guides.
Quick verdict: 1.28 GPF saves water and meets stricter state rules; 1.6 GPF gives a slightly stronger full flush where allowed.
Side-by-side
| 1.28 GPF Toilet | 1.6 GPF Toilet | |
|---|---|---|
| Water per full flush | 1.28 gal | 1.6 gal |
| Allowed nationally | Yes | Yes (federal max) |
| High-efficiency states | Allowed | Not allowed for new installs in some states |
| Annual savings | More | Less |
Check your state
California, Colorado, Texas and Georgia, among others, require 1.28 GPF or lower for new toilets. VEVOR's 1.0/1.28 GPF model fits those rules.
What GPF means
GPF is gallons per flush. Since 1994, US federal law has limited new toilets to 1.6 GPF. High-efficiency toilets (HETs) use 1.28 GPF or less, which is also the threshold for the EPA WaterSense label. Dual-flush toilets have two buttons: a smaller flush for liquids and a full flush for solids, written as e.g. 1.0/1.28 or 1.1/1.6.
How much water you save
Say a household of three flushes 15 times a day. At 1.6 GPF, that's 24 gallons a day; at 1.28 GPF, about 19 gallons. With dual flush and two-thirds of flushes on the small button, the 1.0/1.28 toilet uses roughly 16 gallons. Over a year, that's thousands of gallons, which matters most where water and sewer are billed by volume.
State rules
Several states, including California, Colorado, Texas and Georgia, require new toilets to use 1.28 GPF or less. Building inspectors may flag a 1.6 GPF toilet in a permitted remodel there. Check your state and local rules before buying.
Flush performance
Early low-flow toilets in the 1990s had a reputation for clogging. Modern designs with better trapways and flush mechanisms perform well at 1.28 GPF. If you have old cast iron drain lines with long horizontal runs, ask a plumber; very low flush volumes can carry waste less far in poorly sloped pipes.
Frequently asked questions
Do 1.28 GPF toilets clog more?
Modern designs are engineered for low volume; trapway and flush design matter more than the number.
How do I know my toilet's GPF?
It's often stamped inside the tank or behind the seat.
Can I convert a 1.6 GPF toilet to 1.28?
Dual-flush conversion kits exist, but results vary; replacement is more reliable.
Are 1.28 GPF toilets noisier?
Flush noise depends on design, not volume.
Do low-flow toilets work with septic systems?
Yes, they're common in homes with septic systems.