TOTO 1.28 vs 1.6 GPF: Does Flush Volume Matter?
The short answer
1.28 gallons per flush is the current standard and is required by law in several states. 1.6 GPF is the older standard and uses about 25% more water per flush. On a modern TOTO the flushing performance is effectively the same, so 1.28 is the better default.
What GPF means
GPF is gallons per flush — the volume of water a toilet uses in a single full flush. Federal law has capped it at 1.6 gallons since 1994. WaterSense, the EPA's efficiency programme, requires 1.28 or less.
The practical difference
| 1.28 GPF | 1.6 GPF | |
|---|---|---|
| Water per flush | 1.28 gallons | 1.6 gallons |
| Roughly per year, family of four | About 9,000 gallons | About 11,500 gallons |
| WaterSense certified | Yes | No |
| Legal everywhere in the US | Yes | No — several states require 1.28 |
| Rebate eligible | Often | No |
Around 2,500 gallons a year is the difference for a typical household. At most municipal rates that is a modest saving, but it adds up over the fifteen to twenty-five years a toilet lasts.
One at each flush volume
TOTO Drake Two-Piece Toilet - Universal Height, Elongated
The modern standard. Legal everywhere.
$514.54
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Does 1.6 flush better?
Not on a modern TOTO. This is the assumption that keeps 1.6 models selling, and it comes from the first generation of low-flow toilets in the 1990s, which genuinely did clog.
TOTO's current flushing systems — TORNADO FLUSH, DYNAMAX TORNADO FLUSH and G-Max — were engineered around the lower volume. A 1.28 Drake and a 1.6 Drake use the same bowl and the same flush engineering. If anything, the 1.28 versions are the more recently updated design.
Where flush performance genuinely varies is between series, not between flush volumes within a series.
Where 1.6 is not allowed
Several states have adopted 1.28 GPF as the legal maximum for new toilet installations, including California, Texas, Colorado and Georgia, with others following. If you are in one of those states, a 1.6 toilet is not a legitimate choice for a new installation regardless of preference.
Rules change, so check your local requirements before ordering — but 1.28 is the safe default anywhere in the country.
When 1.6 makes sense
- You are in a state that still permits it, and the model you want is only made in 1.6.
- Your home has old, shallow-slope drain lines and a plumber has specifically recommended more water per flush.
- You are matching an existing toilet in a two-toilet bathroom.
Outside those cases, there is little reason to choose it.
What about 1.0 GPF?
Several TOTO ranges offer a 1.0 GPF toilets version at 1.0 gallons per flush, and some models go lower still. These use TOTO's newer flush engineering and perform well, but they are worth discussing with us if your drain run is long or shallow — very low volumes leave less margin in older plumbing.