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Buying Guide
1.28 vs 1.6 GPF Toilet
GPF = gallons per flush. Florida code allows up to 1.6 GPF, and 1.28 GPF is the WaterSense standard most new toilets meet.
Replacing an old toilet? We help you pick a flush your drain lines can handle and install it. You approve a written quote before any work starts.
Home Therapist serves Tampa Bay, Florida. In the area? FREE estimates and FREE diagnosis.
- Licensed CAC1819196 & CFC1431159
- 4.8 stars from 1,398 reviews
- Background-checked, drug-tested techs
- Hablamos español
At a glance
- Florida code maximum
- 1.6 gpf for any new toilet
- WaterSense standard
- 1.28 gpf or less
- Water saved
- 1.28 uses 0.32 gallons (20%) less per flush than 1.6
- Our pick
- 1.28 gpf for new installs in most Tampa homes; it costs the same
- When 1.6 makes sense
- Old cast iron drain lines or a very long run to the main stack
- What to check
- The MaP score; 800+ grams clears well without double-flushing
- Water Wise rebate
- Up to $100 per WaterSense toilet, $200 if the old one is from 1993 or earlier; 2 per home
- Estimate
- FREE; we check your drain line and rough-in first
Reviewed by Alejandro Morales, Co-Owner & FL Certified Plumbing Contractor (FL license CFC1431159)
Florida Code Background: Why 1.28 GPF Became the Default
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 regional Tampa Bay Water Wise program offers a rebate on WaterSense listed 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. A Tampa Bay Water Wise rebate (up to $100 per WaterSense toilet, or up to $200 when the old toilet was made in 1993 or earlier, limit 2 per home) shortens the payback on a basic WaterSense install.
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 Bay Water Wise Rebate
The regional Tampa Bay Water Wise program pays up to $100 per EPA WaterSense-listed toilet with proof of installation ($40 without it), and up to $200 when the toilet you replace was made in 1993 or earlier or the new one is a 0.8 gpf model. The limit is 2 rebates per home, for the life of the home. You apply online within a year of purchase, and our invoice serves as your proof of installation.
The same program covers water customers of the City of Tampa, St. Petersburg, New Port Richey, Hillsborough County, Pasco County and Pinellas County. Amounts change, so check the current terms before you buy.
What Tampa Bay customers say
“Happy with the service and excellent communication with Home Therapist for help with a plumbing/ drain issue. Can recommend!”
“I had the best experience with this company. From the free estimate to everything in between. I have my beautiful new water heater and more room under my sink when he took the old broken one out. Lester was wonderful and explained everything to me. Highly recommend them.”
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Where we work
We serve the three counties of Tampa Bay from our shop at 1408 W Linebaugh Ave in Tampa.
Hillsborough County
Tampa, Brandon, Riverview, Carrollwood, Town ’n’ Country, Plant City, Ruskin, Sun City Center, Apollo Beach, Valrico, Lutz, Seffner
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Pasco County
Wesley Chapel, Land O’ Lakes, New Port Richey, Holiday, Hudson, Trinity, Zephyrhills, Dade City
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