MaP Flush Test Protocol: How Toilets Are Tested Officially

What Is the MaP Flush Test and Why Does It Exist?

Before MaP testing existed, there was no standardized way to compare flushing power across brands. Manufacturers ran proprietary tests, often with water only, under ideal lab conditions. The result was a wave of complaints as water-saving toilets hit the market -- toilets that met the legal GPF limit but frequently clogged on the first flush.

The MaP program was created through a collaboration between the Canadian Standards Foundation (now CSA Group) and the Veritec Consulting Group, with early support from water utilities across North America. By simulating realistic waste loads, the test gave both regulators and consumers a credible, apples-to-apples performance metric. Today more than 4,000 toilet models have been MaP tested, and the scores are publicly accessible at map-testing.com.

How Exactly Is a MaP Flush Test Conducted?

The Test Media: Soybean Paste

The simulated waste media is a water-packed soybean paste extruded into cylindrical shapes of specific diameter and length to match the physical properties of human solid waste -- including density, compressibility, and behavior in water. Earlier test protocols used actual organic material, but soybean paste became the standard because it is consistent batch to batch, available without biosafety restrictions, and produces repeatable results across different labs.

The media is weighed precisely in grams before placement. After the flush, any residue remaining in the bowl or drainline is collected, dried, and subtracted from the original load. The maximum load that clears 100% in a single flush is the official MaP score.

Water Pressure and Setup Conditions

The standard test pressure is 45 PSI at the supply line to the fill valve. This represents a typical residential water pressure in North America. Some testing programs also evaluate performance at 20 PSI (representing a low-pressure home or upper-floor apartment) and 80 PSI (high-pressure conditions). Scores at reduced pressure are almost always lower than the headline 45 PSI score.

The toilet is installed on a standard test fixture with a fixed trapway exit into a calibrated collection tank. No wax ring modifications, after-market fill valves, or altered flush volumes are permitted. The test uses the toilet exactly as sold at retail, including the tank, flush valve, and trapway.

Test Load Increments

Labs begin at 250 g and step upward in 50 g increments. At each load level, two separate flushes are performed. If both clear completely, the load increases. When the toilet fails to clear a given load (residue remains), the score is recorded as the last fully cleared load. A perfect score of 1,000 g means the toilet cleared 1,000 grams (about 2.2 lbs) of soybean paste in a single flush -- far exceeding what any realistic household use requires.

What MaP Score Do You Actually Need for a Home Toilet?

For most single-bathroom homes with two to four occupants, a MaP score of 500 g to 600 g delivers dependable daily performance without chronic clogging. The 600 g threshold became an informal industry benchmark because it aligns with the median daily waste load across household demographics, with comfortable margin for variance.

Where the score matters most is in commercial settings, family homes with multiple users, or any bathroom that experiences heavy daily traffic. Scores of 800 g and above provide statistical near-certainty against clogging under normal conditions. Plumbers working in multi-unit residential buildings or hospitality construction routinely specify 800 g or 1,000 g models to minimize service calls.

How Do Different Flush Technologies Score in MaP Testing?

Gravity-Fed Systems

Gravity-fed toilets use the weight of falling water from an elevated tank to generate flush pressure. The key performance variables are the flush valve diameter (3-inch valves release water faster than 2-inch), the bowl-to-trapway geometry, and the trapway diameter. Models with 3-inch or larger flush valves combined with wide, fully glazed trapways consistently achieve high MaP scores. The TOTO Drake line is the most commonly cited example -- its G-Max flushing system uses a 3-inch flush valve and a 2-1/8-inch trapway to reach 1,000 g on 1.6 GPF configurations.

Pressure-Assisted Systems

Pressure-assisted toilets store compressed air above the water in a sealed vessel inside the tank. When triggered, the compressed air drives water into the bowl at higher velocity than gravity alone allows. This typically results in MaP scores of 800 g to 1,000 g and very complete bowl clearing, but the noise level (a loud whoosh) limits these models primarily to commercial applications. Brands like Sloan and Flushmate manufacture the pressure-assist vessels used inside OEM toilet tanks from multiple manufacturers.

Dual-Flush Systems

Dual-flush toilets offer a reduced-volume flush (typically 0.8 GPF) for liquid waste and a full flush (1.28 GPF or 1.6 GPF) for solid waste. MaP scoring applies to the full-flush mode. High-quality dual-flush models from TOTO (Aquia IV: 1,000 g at 1.28 GPF full flush) and Kohler perform well. Budget dual-flush models from less-known manufacturers may score as low as 350 g to 500 g on the full cycle, particularly when the flush valve is smaller or the trapway is poorly optimized.

Tankless and Wall-Hung Systems

Wall-hung toilets use an in-wall carrier frame with a separate flush tank concealed behind the wall. Performance varies significantly by the flush valve unit (often called a carrier or actuator plate). High-end wall-hung models using Geberit, TOTO, or Kohler carrier systems score 500 g to 1,000 g. Lower-cost wall-hung units with inferior actuator plates may score below 500 g. Swiss Madison offers wall-hung options at accessible price points; their Sublime series uses a Geberit-compatible carrier for reliable flush performance.

How Does MaP Testing Relate to EPA WaterSense Certification?

The relationship between the two programs is complementary rather than redundant. WaterSense is administered by the EPA and focuses on water conservation; it guarantees a toilet will not waste water beyond a defined threshold. MaP testing is administered independently by Veritec and alliance members; it guarantees a toilet can actually flush effectively. Together, a toilet that is both WaterSense certified and MaP-tested at 600 g or above delivers both conservation and performance.

When shopping for toilets, look for both labels. A WaterSense logo on the box confirms the 1.28 GPF limit. A MaP score (printed on the spec sheet, packaging, or lookup at map-testing.com) confirms how well that low volume of water actually performs. These two numbers together are more useful than either one alone.

Many utility companies across the United States offer rebates of $50 to $200 on WaterSense-certified toilets. Several rebate programs have adopted additional MaP floors of 500 g or 600 g above the EPA's 350 g minimum, recognizing that occupant satisfaction requires meaningful performance as well as water savings.

For a complete look at how these scores factor into buying decisions, see the best flushing toilets guide, which filters top-ranked models by MaP score and WaterSense status.

Can a Toilet's MaP Score Change Over Time or Be Retested?

This is a meaningful caveat. Several cases have been documented where an older model number carries a legacy MaP score from a previous generation of the toilet, while the current production version has different internals. The safest approach is to check the map-testing.com database directly and note the test year. Scores more than five years old for models with multiple production runs should be treated with some skepticism unless the manufacturer confirms the current production design is unchanged.

Consumers with older toilets may also wonder whether their existing toilet would score differently after years of use. Trapway accumulation of mineral scale, worn flush valves, or degraded fill valves can all reduce effective flush performance below the original MaP score. Annual inspection of the flush valve and periodic descaling of the trapway preserves close-to-original performance.

Third-Party vs. First-Party Testing

All official MaP testing is performed by accredited independent laboratories -- not by manufacturers. A manufacturer cannot self-certify a MaP score. Testing must follow the published protocol, and results are submitted to the MaP program for inclusion in the public database. This separation between manufacturer and tester is what makes MaP scores credible for comparison purposes.

Some manufacturers publish internal testing data using "MaP-like" methods without formal accreditation. These self-reported numbers should not be equated with official MaP scores. The only scores that carry the independent MaP validation are those listed in the official database at map-testing.com.

Related reading: trapway size and diameter guide | TOTO Drake in-depth review | GPF and water usage explained

Which Brands Consistently Lead MaP Scores?

Across the publicly available MaP database, certain brands appear disproportionately in the 800 g to 1,000 g tier. TOTO leads by model count in the top tier, driven by its G-Max (3-inch valve, large trapway) and TORNADO FLUSH (rim-less dual-nozzle) technologies. The TOTO Drake family, which spans multiple configurations across 1.6 GPF and 1.28 GPF, achieves 1,000 g across all variants.

American Standard's Champion 4 has maintained a 1,000 g MaP score since its introduction, making it one of the most consistently referenced high-score gravity toilets in the United States. Its 4-inch accelerator flush valve and fully glazed 2-3/8-inch trapway -- the largest commercial gravity trapway available from a major brand -- explain the score. Note that the Champion 4 uses 1.6 GPF and is not WaterSense certified; the Champion 4 Max variant offers 1.28 GPF at 1,000 g with WaterSense status.

Kohler's AquaPiston flush valve technology, used in the Cimarron, Highline, and several other Kohler lines, delivers reliable 800 g to 1,000 g scores at 1.28 GPF. The AquaPiston design uses a canister valve that opens from the center outward, releasing water at 360 degrees rather than from one side, resulting in a more complete bowl rinse and higher solid clearance.

Gerber Plumbing, a less-marketed but professionally respected brand, produces several models rated at 800 g and above. The Gerber Viper line at 1.0 GPF (ultra-high efficiency) achieves 600 g, a notable achievement at that water volume. Gerber is commonly specified by plumbing contractors in commercial renovation projects.

Woodbridge, a mid-market brand popular on Amazon, offers its T-0001 one-piece with an 800 g MaP score at 1.28 GPF WaterSense. While not at the 1,000 g ceiling, this score is sufficient for residential use and the model's one-piece design simplifies cleaning.

Swiss Madison's Sublime and St. Tropez wall-hung lines use Geberit-compatible carriers and score in the 500 g to 800 g range depending on configuration, making them competitive for modern bathroom remodels where a wall-hung aesthetic is prioritized.