Buying Guide
1.28 vs 1.6 GPF Toilet
GPF = gallons per flush. Current Florida code is 1.28 GPF standard.
Quick Verdict
1.28 GPF (WaterSense standard): current Florida code, saves 20% water vs 1.6 GPF, same price. 1.6 GPF: older standard, still allowed in commercial. Pre-1994 toilets (3.5-5 GPF): should be replaced, wastes water + often underperforms. Call (813) 343-2212.
1.28 GPF vs 1.6 GPF
| Feature | 1.28 GPF | 1.6 GPF |
|---|---|---|
| Water per flush | 1.28 gallons | 1.6 gallons |
| Annual water use (4-person home) | ~10,000 gal | ~12,500 gal |
| Cost difference | Same | Same |
| Flush power | Equal or better (modern) | Legacy |
| Florida code compliance | Yes (current) | Yes (grandfathered) |
| WaterSense label | Yes | No |
| Water utility rebate eligible | Often | No |
What We Recommend
Always pick 1.28 GPF for new installs in Tampa. Same price, saves water. Modern pressure-assist designs flush as well or better than old 1.6 GPF.
Some Tampa utilities offer rebates for replacing old 1.6 or 3.5 GPF toilets with 1.28 GPF WaterSense models.
FAQ
Weak flush myth?
Old 1990s 1.6 GPF toilets had weak flushes. Modern 1.28 GPF with pressure-assist or vortex design flushes better than those old 1.6 GPF units.
Dual-flush worth it?
Very minor water savings beyond 1.28 GPF. Often confusing for guests. Skip unless specifically required.
Replace old 3.5 GPF?
Yes, $299-$999 install pays back in 2-3 years of water bill savings.
Florida Code Background: Why 1.28 GPF Is Standard Now
Federal plumbing code caps new toilet flush volume at 1.6 gallons per flush (GPF). The EPA WaterSense label requires 1.28 GPF or less, and the City of Tampa offers a rebate on WaterSense certified replacements. Anything over 1.6 GPF is no longer legal to install as new construction or retrofit in Florida. If your current toilet is 3.5 GPF (pre-1994) or 1.6 GPF, you are running legacy hardware.
The question is not really “which do I buy” since 1.28 GPF has become the default at every plumbing supply house from Ferguson to Home Depot. The real question is whether 1.28 GPF performs well enough to avoid double-flushing, which defeats the water-savings purpose.
Real Tampa Water Savings Math
A 4-person household flushing 5 times per person per day generates 20 daily flushes. Over a year:
| Toilet Type | Annual Water Use | Tampa Water Cost Annual |
|---|---|---|
| Pre-1994 3.5 GPF | 25,550 gallons | $166 |
| Standard 1.6 GPF | 11,680 gallons | $76 |
| WaterSense 1.28 GPF | 9,344 gallons | $61 |
Upgrading a 3.5 GPF to a 1.28 GPF saves about $105 per year per toilet. In a 3-toilet home, that is $315/year. The Tampa Water Department rebate ($100 per toilet, up to 3 toilets) covers most of a basic WaterSense install, making the payback nearly immediate.
MaP Scores: What Actually Matters for 1.28 GPF
Maximum Performance (MaP) testing measures how many grams of solid waste a toilet can clear in a single flush. MaP is scored in grams (higher is better). The industry threshold for “good performance” is 500 grams. Elite performance starts at 800 grams. Anything over 1,000 grams is excellent.
Here is the reality: not all 1.28 GPF toilets perform equally. A cheap builder-grade 1.28 GPF often scores 350-500 grams MaP, which means you will double-flush regularly. A quality 1.28 GPF scores 800-1,000 grams MaP and clears as well as old 3.5 GPF.
High-MaP 1.28 GPF Models We Install
- Kohler Cimarron Comfort Height (K-3609): 1,000 gram MaP, 12-inch rough-in, ADA height. $279-$349 installed.
- Toto Drake II: 800 gram MaP, Tornado Flush, comfort height option. $329-$399 installed.
- American Standard Champion 4: 1,000 gram MaP, 4-inch flush valve. $279-$349 installed.
- Kohler Wellworth Dual Flush: 1.28/1.0 GPF dual flush. $289-$359 installed.
Why 1.6 GPF Still Exists
You can still buy 1.6 GPF toilets because they are legal (just not WaterSense certified). Where do they make sense in Tampa?
- Older cast iron drain lines: South Tampa, Seminole Heights, parts of St. Pete with pre-1970 cast iron sometimes benefit from 1.6 GPF extra water volume to prevent clogs. Not because 1.28 GPF cannot clear waste (the toilet is fine), but because the drain line is rough-interior and needs more water for scouring.
- Pressure-assisted toilets: Some commercial-grade pressure-assist toilets come in 1.6 GPF configurations. These use stored water pressure to generate a strong flush. Loud but extremely effective.
- Slab-on-grade homes with long drain runs: Ranch layouts where the master bath is 30+ feet from the main stack sometimes clear better on 1.6 GPF.
Tampa Water Department Rebate
City of Tampa offers a $100 rebate per WaterSense 1.28 GPF toilet, up to 3 toilets per household, when replacing an older 1.6 GPF or larger model. Application submitted after install with proof of purchase and the old toilet disposed. We include the rebate paperwork with every toilet replacement install.
Hillsborough County (outside Tampa city limits) has a similar rebate through the Water Conservation Team: $50 per WaterSense toilet, up to 2 per household. Pinellas County programs vary by municipality.
Frequently Asked Questions
Will a 1.28 GPF toilet clog more often than my old 1.6 GPF?
Not if you buy a toilet with a high MaP score (800+ grams). A cheap 1.28 GPF builder-grade toilet with a 400-gram MaP will clog more often. This is where brand and model selection matters.
Should I double-flush on a 1.28 GPF?
Occasional double-flushing wastes the water-savings benefit. If you double-flush regularly, the toilet is undersized or underperforming. Check the MaP score, or call us for an upgrade.
Do I need to upgrade all three toilets at once for the Tampa rebate?
No. The $100 rebate applies per toilet, up to 3 total. You can replace one at a time as budget allows and claim each rebate separately.
What about pressure-assisted toilets?
Pressure-assisted toilets (Kohler Wellworth Pressure Lite, Gerber Avalanche) use stored air pressure to generate a more forceful flush. They are louder but almost never clog. Good choice for homes with older drain lines. $449-$649 installed.
How long does installation take?
Standard toilet replacement is 60-90 minutes per toilet. We haul away the old toilet and handle disposal. Wax ring, closet bolts, supply line included.
Will a 1.28 GPF work with my older plumbing?
Usually yes. If you have cast iron drain lines that are 60+ years old and rough internally, we sometimes recommend a high-MaP model over a basic 1.28 GPF. FREE diagnosis during the estimate.
What is dual flush?
Dual flush toilets have two buttons: a partial flush (usually 1.0 GPF for liquid waste) and a full flush (1.28 GPF for solid). Kohler Wellworth Dual Flush and American Standard H2Option are common examples. Real-world water savings vs straight 1.28 GPF: modest, maybe 10 percent.
How do I measure my existing rough-in?
Measure from the finished wall behind the toilet to the center of the closet bolts on the floor. 12 inches is standard, 10 inches (pre-1970 Tampa homes) and 14 inches (some newer builds) exist. Buy the right rough-in for your existing plumbing.
Call (813) 343-2212 for FREE toilet replacement estimates with Tampa rebate paperwork included. Licensed CFC1431159.