MaP Testing and Water Efficiency: How They Interact

Buying a toilet without checking both MaP scores and water-use ratings is like buying a car based only on fuel economy without checking whether it can actually merge onto a highway. Both metrics matter. Both have limits. And the interaction between them determines whether your toilet will perform reliably for a decade or leave you reaching for a plunger twice a week.

This guide explains the mechanics behind each standard, shows how they are interrelated, and gives you the data you need to identify models that genuinely deliver on both dimensions. For a broader look at top performers across all categories, see our guide to the best flushing toilets on the market.

MaP (Maximum Performance) testing measures the maximum mass of simulated waste -- expressed in grams -- that a toilet can flush and clear completely in a single flush cycle. Scores range from under 250 grams (poor) to 1,000 grams (perfect, the protocol ceiling). A score of 500 grams or above is generally considered acceptable for residential use; 800+ grams is recommended for households with heavy use or a history of clogging.

Recommended toilets in this guide

TOTO Drake II

Check price on Amazon

TOTO Aquia IV

Check price on Amazon

TOTO UltraMax II

Check price on Amazon

Kohler Cimarron

Check price on Amazon

The MaP testing protocol was developed jointly by the Canadian Water and Wastewater Association (CWWA) and a consortium of U.S. water utilities starting in 2003. The test uses a standardized simulated waste medium -- a miso paste and soybean casing combination designed to approximate the density, cohesion, and diameter of real human waste -- along with a specified volume of toilet paper. The objective is to determine the maximum mass a toilet can reliably evacuate without any residue remaining in the bowl or trap.

The test is conducted at a standardized static water pressure to simulate typical residential conditions. Each toilet is flushed multiple times at incrementally increasing waste loads. The highest load at which the toilet clears 100 percent of the media on every attempt is recorded as the MaP score. The test is third-party administered; manufacturers submit toilets voluntarily, and results are published publicly at map-testing.com.

What MaP Score Thresholds Mean in Practice

MaP Premium certification -- a designation introduced to recognize toilets that combine high performance with low water use -- requires a minimum score of 350 grams at 1.0 GPF or less. This is the strictest benchmark in residential toilet testing and has been adopted by several water utilities as a rebate qualification threshold.

The EPA launched WaterSense in 2006 as a market-transformation initiative modeled on the Energy Star program. For toilets, WaterSense certification requires two things: a water use at or below 1.28 GPF and a demonstrated flush performance meeting the program's minimum standard. The performance standard is tested using the MaP protocol, which is why the two systems are fundamentally linked.

According to EPA data, a WaterSense-certified toilet saves approximately 13,000 gallons of water per year compared to a 3.5 GPF toilet from the pre-1994 era, and roughly 4,000 gallons per year compared to a standard 1.6 GPF toilet. For a household of four, that represents meaningful annual utility cost savings in most U.S. markets.

WaterSense vs. Standard vs. High-Efficiency: The GPF Breakdown

State-level regulations in California, Colorado, Georgia, and Texas have adopted WaterSense as a minimum standard for new construction and replacement toilets, making the certification de facto mandatory in large portions of the U.S. residential market. See our in-depth article on EPA WaterSense explained for more on the certification process.

The conventional assumption -- less water equals less flush power -- was accurate when toilet designs were essentially passive gravity systems with large tanks and simple trapways. Early low-flow mandates in the 1990s did produce a generation of underperforming toilets because manufacturers simply reduced tank size without redesigning the hydraulic system. The backlash was significant enough that Congress briefly exempted certain states from low-flow requirements.

Modern engineering has fundamentally changed this dynamic. The key innovations driving high MaP scores at low GPF include:

• Large-diameter fully glazed trapways: A 2.125-inch or larger fully glazed trapway (as used in the TOTO Drake and Drake II) reduces friction and allows faster waste evacuation with less water volume.
• Optimized bowl geometry: Elongated bowls with precisely angled rim jets create a directed vortex that uses kinetic energy -- not raw water volume -- to clear waste.
• Wide-flush valves: A 3-inch flush valve (vs. the older 2-inch standard) releases water faster, creating a stronger initial surge that compensates for reduced total volume.
• Pressure-assisted designs: Brands like Flushmate and Gerber use pressurized air to amplify flush force far beyond what gravity alone can achieve, enabling sub-1.0 GPF operation at MaP scores above 800 grams.
• TOTO's Tornado Flush and Double Cyclone: These rim-jet configurations eliminate the traditional under-rim channels, directing two or three powerful water streams tangentially to the bowl, cleaning and clearing with significantly less water.

For a deeper look at how flow rates affect real-world performance, see our guide comparing 1.28 GPF vs. 1.6 GPF toilets.

A few observations worth noting from this data set. First, the TOTO Aquia IV achieves a perfect 1,000-gram MaP score as a dual-flush toilet, which was once considered impossible for a non-pressure-assisted design. The Tornado Flush system's directed water jets and the bowl's steep angle account for the performance. Second, the Woodbridge T-0001 -- a popular budget-tier dual-flush model -- achieves a respectable 800-gram score at a 0.8 GPF partial flush, which places it in the high-efficiency category without a premium price.

Third and most importantly: the American Standard Champion 4's 1,000-gram score at 1.6 GPF is not necessarily better in practice than the TOTO UltraMax II's matching 1,000-gram score at 1.28 GPF. For typical household solid waste loads, 1,000 grams represents several times the actual load per flush, so the practical difference is negligible. Both toilets clear normal waste reliably; the Champion 4 simply uses 25 percent more water per flush to get there.

The MaP Premium designation was introduced to address a gap in the market: as water utilities pushed for toilets using less than 1.0 GPF, there was no independent standard to verify that these ultra-low-flow models actually worked. Some 0.8 GPF designs that appeared on the market in the 2010s had MaP scores below 200 grams -- functionally useless for household solid waste despite their impressive water-use numbers.

To qualify for MaP Premium, a toilet must:

• Use no more than 1.0 GPF (or 1.1 GPF for pressure-assisted models per some program versions)
• Achieve a MaP score of at least 350 grams at that water volume
• Pass the standard MaP testing protocol under third-party supervision

In practice, the most competitive MaP Premium models significantly exceed the 350-gram minimum. The TOTO Aquia IV dual-flush achieves 1,000 grams at its full-flush volume (1.28 GPF) and still clears substantial loads at the 0.9 GPF partial flush. The Niagara Stealth, a 0.8 GPF gravity-fed model, achieves approximately 500 grams at its single low-flow setting -- well above the MaP Premium threshold despite using half the water of a 1.6 GPF toilet.

For more on how high-efficiency designations interact with real-world water savings, see our article on high-efficiency toilets explained.

TOTO: Tornado Flush and G-Max

TOTO's G-Max system, found on the Drake and Drake I, uses a 3-inch flush valve and a large 2.125-inch fully glazed trapway to achieve 800+ grams at 1.6 GPF. The successor Drake II replaces G-Max with the Double Cyclone system -- two nozzles that direct water in a centrifugal pattern, improving bowl coverage and reducing water use to 1.28 GPF while maintaining 800+ grams. The UltraMax II and Aquia IV use the Tornado Flush, TOTO's current flagship, which achieves 1,000 grams at 1.28 GPF on certain models.

American Standard: Champion 4 and PowerWash

The Champion 4's defining feature is its 2.375-inch trapway -- the widest of any major residential toilet -- paired with a 4-inch flush valve aperture (the "Champion" designation refers to this valve size). At 1.6 GPF, this combination achieves a perfect 1,000-gram MaP score. The Cadet 3 uses a narrower trapway but adds PowerWash Rim technology -- angled rim jets that clean the bowl while improving waste evacuation -- to achieve 800 grams at 1.28 GPF. The EverClean antimicrobial surface treatment on both models maintains hydraulic performance over time by inhibiting the biological buildup that can reduce flush effectiveness.

Kohler: Class Five and AquaPiston

Kohler's Class Five flushing system pairs a 3-inch canister flush valve (the AquaPiston) with an optimized trapway and a precision-engineered bowl. The canister design opens from all sides simultaneously rather than pivoting like a traditional flapper, releasing water faster and creating a stronger initial surge. The Cimarron achieves a perfect 1,000 grams at 1.28 GPF with this system. The Highline uses the same valve but with a slightly different bowl geometry, achieving approximately 600 grams -- effective but well below the Cimarron's performance ceiling.

Gerber and Flushmate: Pressure-Assist

Pressure-assist systems like those used in the Gerber Ultra Flush store compressed air in a sealed vessel inside the tank. When the flush is triggered, the compressed air propels water into the bowl with force that gravity cannot replicate. This allows Gerber's pressure-assist models to achieve MaP scores of 800 to 1,000 grams at just 1.0 to 1.1 GPF. The trade-off is noise (pressure-assist flushes are noticeably louder than gravity-fed designs) and a higher upfront cost for the vessel cartridge replacement over time.

Here is a practical decision framework for applying both metrics:

Step 1: Set Your MaP Floor Based on Household Profile

• Single adult or couple, light use: MaP 500+ is sufficient
• Family of 3 to 4, standard use: MaP 600+ is the minimum; 800+ is recommended
• Large family, heavy use, or history of clogs: MaP 800+ required; 1,000 grams ideal
• Guest bathroom, vacation rental, or commercial light-duty: MaP 500+ with WaterSense compliance

Step 2: Set Your GPF Ceiling Based on Regulatory and Financial Goals

• Replace a 1.6 GPF toilet, no rebate program available: 1.28 GPF with WaterSense
• Utility rebate program available: Check whether MaP Premium (1.0 GPF) qualifies; if so, consider the Niagara Stealth or TOTO Aquia IV partial flush
• LEED or green building certification: MaP Premium required; 1.0 GPF or below
• No water restrictions, maximize performance: 1.6 GPF models (Champion 4) deliver the highest MaP scores

Step 3: Cross-Reference Published MaP Scores

Do not rely on manufacturer marketing language like "powerful flush" or "no-clog design" without verifying the published MaP score at map-testing.com. The database lists scores by brand, model number, and water volume, making it straightforward to confirm whether a specific SKU meets your performance threshold. Note that MaP scores can vary between color variants or model years of the same toilet line, so confirm the score for the exact model number you are purchasing.

Also see our guide to the toilet MaP score explained for a deeper walk-through of the testing protocol and how to read the database.

MaP testing is the most rigorous independent flush-performance standard available, but it has documented limitations that informed buyers should understand.

Simulated vs. Real Waste

The miso paste and soybean casing medium used in MaP testing approximates real waste in density and cohesion but does not replicate all conditions encountered in real households. Toilet paper type (ultra-thick, double-ply, wet wipes), waste consistency, and mixed loads can produce results that diverge from MaP scores. American Standard acknowledges this in its Champion 4 marketing by noting that the 2.375-inch trapway is specifically designed to handle "anything that should be flushed," recognizing that real-world loads are less controlled than test conditions.

Pressure Assumptions

MaP testing is conducted at a standardized static water pressure. Homes with low incoming water pressure -- common in older urban buildings or rural properties with well systems -- may see lower real-world flush performance than MaP scores suggest. Conversely, high-pressure supply lines (above 80 PSI) can improve gravity-flush performance beyond the tested value.

Drain-Line Carry Is Not Measured

MaP testing only measures bowl clearance -- whether the waste exits the toilet trap. It does not measure drain-line carry, which refers to how far waste travels down the horizontal drain pipes once it leaves the toilet. Homes with long horizontal drain runs, reduced-slope pipes (less than 1/4 inch per foot), or partially blocked drain lines may experience different results than MaP scores indicate, regardless of bowl-clearance performance.

One-Time Test at New Condition

MaP testing is conducted on new toilets under controlled laboratory conditions. Mineral deposits, scale buildup inside the trapway, worn flappers, reduced tank refill water level, and degraded rim jets can all reduce effective flush performance below the rated MaP score over time. A toilet rated at 800 grams new may effectively perform closer to 500 grams after five years of hard-water use without cleaning and maintenance.

The economic argument for WaterSense-certified toilets depends on your local water rate, household flush frequency, and the cost differential between efficient and standard models. Here is the framework:

Estimated Annual Water Savings by Toilet Type

Assuming 5 flushes per person per day at the U.S. average of $0.004 per gallon (national average, which varies significantly by municipality):

At national average water rates, the payback period on a WaterSense toilet replacing a 1.6 GPF model is typically 15 to 25 years based on water savings alone. The financial case is stronger in high-rate markets (San Francisco, New York City, parts of Texas) where water costs two to four times the national average, or when utility rebates are available. Replacing a pre-1994 toilet makes strong financial sense in almost any market.

The practical takeaway: do not buy a less-capable toilet solely to save water if clog-related service calls become necessary. A single plumber visit to address a chronic clog issue costs more than the lifetime water savings from choosing a lower-GPF model.

Dual-flush toilets offer two flush volumes -- typically 0.8 or 1.0 GPF for liquid waste and 1.28 or 1.6 GPF for solid waste -- and are theoretically more efficient than single-flush designs because the lower volume handles a significant portion of daily flushes. In practice, the efficiency gain depends entirely on user behavior.

Studies by water utilities in Australia (where dual-flush is the dominant design) and in U.S. pilot programs have found that in households where occupants consistently use the partial flush for liquid waste, average effective GPF drops to approximately 0.95 to 1.05, representing a 20 to 35 percent reduction in toilet water use compared to a single-flush 1.28 GPF toilet. However, in households where occupants default to the full flush for all waste types (a common real-world behavior, particularly in shared or rental occupancies), the effective GPF is essentially equal to the full-flush volume.

For MaP scoring purposes, dual-flush toilets are typically scored at the full-flush volume. The partial-flush MaP score is sometimes published separately and is frequently not tested at all. The Woodbridge T-0001 and TOTO Aquia IV are notable exceptions -- both have published MaP scores at both flush volumes, allowing a complete assessment of dual-flush performance.

For a full comparison of flush options, see our guide on dual-flush vs. single-flush toilets.

• EPA WaterSense, epa.gov/watersense
• MaP flush testing, map-testing.com
• Manufacturer published specifications
• CWWA (Canadian Water and Wastewater Association) MaP program documentation
• EPA WaterSense Specification for Tank-Type Toilets, Version 1.1
• California Energy Commission and California Department of Housing, Title 20 and CALGreen standards

• Best Flushing Toilets: Top Picks for 2026
• EPA WaterSense Explained: What the Label Really Means
• Toilet MaP Score Explained: How to Read the Database
• High-Efficiency Toilets Explained: HET vs. UHET vs. MaP Premium
• Dual-Flush vs. Single-Flush Toilets: Which Saves More Water?