Kohler AquaPiston Flush: How It Works and Why It Matters
A deep dive into Kohler's canister-based flush valve technology, how it stacks up against competitors, and what the engineering actually delivers for everyday performance.
Why Trust Best Flushing Toilets
- Flushing power and MaP flush-test scores
- Water efficiency (GPF and EPA WaterSense)
- Aggregated owner reviews
- Clog resistance and trapway design
- Brand reliability and warranty
Research updated June 2026.
Quick Answer
The Kohler AquaPiston is a canister-style flush valve that opens 360 degrees to deliver a powerful, consistent flush. It earns MaP scores up to 1,000 grams, achieves EPA WaterSense certification at 1.28 GPF, and dramatically reduces the mechanical parts most likely to fail or leak compared to a traditional flapper.
What Exactly Is the Kohler AquaPiston?
The Kohler AquaPiston is a canister-shaped flush valve that sits at the center of the toilet tank and replaces the conventional rubber flapper found on most American toilets. Rather than lifting a hinged flap at one side, the canister rises straight up from a sealed seat, allowing water to rush into the bowl simultaneously from all sides through a full 360-degree opening. Kohler introduced the design as a direct response to the chronic seal failures and weak partial-bowl coverage that plagued flapper valves, particularly at the low 1.28 GPF volumes mandated after federal efficiency rules tightened.
Before the AquaPiston, the transition from 3.5 GPF toilets to 1.6 GPF and then 1.28 GPF was a reliability nightmare. Manufacturers were forced to push the same water volume harder through the same trapway geometry, and flapper valves were never really designed for that kind of hydraulic demand. The flap itself is buoyant on one axis, meaning it opens from one edge and water enters the bowl in an arc rather than a ring. At high GPF that asymmetry is masked by sheer volume. At 1.28 GPF it means the water never quite reaches the far side of the bowl with equal force.
Kohler's answer was to engineer around the flapper entirely. The canister sits on a circular seat and rises vertically, so the opening geometry is annular: water accelerates through a ring rather than a half-moon. The physics are meaningfully different. A ring jet distributes kinetic energy evenly around the bowl's rim holes and siphon jet port, while a half-moon jet concentrates energy on one side and lets the other side lag. That symmetry is the central mechanical claim of the AquaPiston, and it is the single factor most responsible for the toilet's MaP performance.
MaP (Maximum Performance) testing is an independent protocol developed by the Canadian Water and Wastewater Association and Veritec Consulting that measures how many grams of solid waste a toilet can clear in a single flush. A score of 500 g passes the bar for adequate residential performance. A score of 800 g or above is considered high performance. Toilets using the AquaPiston -- including the Kohler Cimarron, Highline, and Wellworth -- routinely score between 800 g and 1,000 g (the test ceiling) in published MaP data, placing them consistently in the top tier of efficiency-era toilets.
How Does the AquaPiston Actually Work Mechanically?
When the flush handle is pushed, it lifts a sealed canister straight up off a circular valve seat using a chain or direct linkage. Water in the tank floods through the newly opened ring-shaped gap from all 360 degrees simultaneously, channeling into the bowl through rim holes and the siphon jet port in a coordinated surge. Once the tank empties below a set threshold, the canister drops back onto the seat by gravity, resealing the valve and allowing the fill cycle to begin.
The canister body is made from a durable plastic that Kohler says is resistant to chloramines, chlorine, and hard-water mineral deposits. The sealing surface is a low-friction gasket around the canister's base. In traditional flapper designs, the rubber disc must flex, warp, and seal against a flat seat repeatedly. Over time, chloramine exposure causes the rubber to stiffen and shrink, and mineral buildup on the seat face creates microchannels that leak. The AquaPiston gasket sits in a protected groove and makes contact with a machined plastic seat rather than a rough ceramic edge, which is why Kohler claims significantly longer service life.
The lift mechanism itself is a departure from flapper designs too. Flappers use a buoyancy and chain system: the chain pulls the flap up, buoyancy holds it aloft until the tank empties, then gravity drops it closed. If the chain is too short, the flap never fully opens. If it is too long, it gets under the flap and causes slow leaks. With the AquaPiston, the lift is a direct vertical stroke. There is no buoyancy reliance. The canister stays open for a consistent duration tied to tank volume rather than to the vagaries of chain length, buoyancy, or water chemistry affecting rubber elasticity.
Partial-flush models (the Class Five and AquaPiston Dual Flush variants used in toilets like the Aquia series) add a second trip lever that lifts the canister only partway, releasing roughly 0.8 GPF for liquid waste. The same 360-degree geometry applies; the canister simply travels a shorter vertical distance before the secondary mechanism drops it. This makes dual-flush AquaPiston toilets notably more reliable than dual-flush flapper designs, where partial-flush buttons have a reputation for sealing problems at the flap's partial-open position.
The practical consumer-facing proof is in warranty claims and owner review patterns. Across thousands of aggregated reviews on major retail platforms, Kohler toilets with the AquaPiston consistently receive fewer complaints about phantom flushing, running water, and seal replacement compared to same-era flapper-based competitors. That is a meaningful signal given that seal failure is the most common toilet maintenance complaint in owner reviews across all major brands.
What MaP Score Does the AquaPiston Achieve, and Why Does That Number Matter?
Kohler toilets equipped with the AquaPiston, such as the Cimarron and Highline Arc, score 1,000 grams (the maximum) on MaP testing at 1.28 GPF, meaning they clear the full test load in a single flush at a water-efficient volume. A MaP score of 1,000 g at 1.28 GPF is significant because it proves the toilet does not need the extra 0.32 gallons per flush that older 1.6 GPF toilets used, delivering equivalent or superior performance at 20 percent less water.
MaP testing was created specifically because the efficiency transition from 3.5 GPF to 1.6 GPF produced a generation of toilets that technically used less water but required multiple flushes per visit, defeating the efficiency goal. By the early 2000s, consumers had developed a justified mistrust of low-flow toilets. MaP was designed to give buyers an objective benchmark: if a toilet scores 500 g or more, it reliably clears a representative solid waste load in one flush at its rated GPF. If it scores 800 g or more, it has a meaningful margin of safety.
The AquaPiston's 1,000 g scores at 1.28 GPF matter for several reasons beyond bragging rights. First, they validate that the 360-degree opening geometry actually delivers better hydraulic performance than a single-axis flapper at the same GPF. Second, they mean households with multiple occupants, older plumbing, or longer drain runs to the main stack have a real engineering buffer against clogs. Third, the scores come from an independent third-party protocol, not manufacturer self-testing, so they are comparable across brands.
For context: the best flushing toilets in the residential market -- TOTO Drake II, American Standard Champion 4, Kohler Cimarron -- all reach 1,000 g. The differentiator is not the score ceiling but which toilets hit it at 1.28 GPF versus 1.6 GPF. The AquaPiston achieves 1,000 g at 1.28 GPF, placing Kohler's lineup firmly in the EPA WaterSense tier without performance compromise.
How Does the AquaPiston Compare to Competitors Like TOTO's G-Max and American Standard's PowerWash?
The AquaPiston, TOTO's G-Max, and American Standard's PowerWash/Vormax all aim for 1,000 g MaP scores with EPA WaterSense certification, but they approach the hydraulics differently: TOTO uses a wide 3-inch flush valve with a glazed straight trapway and a large siphon jet, American Standard relies on an asymmetric rim-free bowl with a concentrated jet, and Kohler uses the canister valve with a fully skirted or standard trapway. Each strategy achieves similar MaP results but with different maintenance profiles and bowl-cleaning characteristics.
| Technology | Brand / Model | Flush Type | GPF | MaP Score | WaterSense | Valve Design | Check Price |
|---|---|---|---|---|---|---|---|
| AquaPiston | Kohler Cimarron | Single | 1.28 | 1,000 g | Yes | 360-degree canister | Check price |
| AquaPiston Dual | Kohler Aquia IV | Dual (0.8 / 1.28) | 0.8 / 1.28 | 1,000 g (full) | Yes | 360-degree canister | Check price |
| G-Max | TOTO Drake II | Single | 1.28 | 1,000 g | Yes | 3-inch flapper | Check price |
| Tornado Flush | TOTO UltraMax II | Single | 1.28 | 1,000 g | Yes | Dual nozzle rim | Check price |
| PowerWash Rim | American Standard Cadet 3 | Single | 1.28 | 1,000 g | Yes | 3-inch flapper | Check price |
| VorMax | American Standard Vormax | Single | 1.28 | 1,000 g | Yes | 3-inch flapper | Check price |
| EverClean / Champion 4 | American Standard Champion 4 | Single | 1.6 | 1,000 g | No (1.6 GPF) | 4-inch flapper | Check price |
| Dual Flush | Woodbridge T-0001 | Dual (0.8 / 1.6) | 0.8 / 1.6 | ~600 g (full) | Avg. compliant | Button-actuated canister | Check price |
TOTO's G-Max system, used in the Drake and Drake II, is perhaps the most direct competitor. G-Max uses a 3-inch flapper rather than a canister, but compensates with a large siphon jet port, a deeply glazed straight trapway (2-1/8-inch minimum diameter), and a fully glazed interior bowl. The larger flapper opening delivers a faster water release, which TOTO has tuned to score 1,000 g. The trade-off: flapper replacement remains necessary over time, though TOTO's materials have improved significantly. The Drake II's 1.28 GPF G-Max is widely regarded as one of the most reliable single-flush toilets available, and its parts are universally stocked at hardware stores.
American Standard's Champion 4 uses a massive 4-inch flapper -- the largest in mainstream residential production -- to blast 1.6 GPF through a wide trapway. It achieves 1,000 g easily but at the cost of 20 percent more water per flush than WaterSense-rated toilets. The Cadet 3 and Vormax bring American Standard into the 1.28 GPF tier with 3-inch flappers, and both achieve high MaP scores with the PowerWash rim design that uses concentrated rim jets rather than the traditional drilled-hole ring.
The AquaPiston's durability advantage over flappers becomes clearest at the 5- to 10-year mark. Rubber flappers in markets with chloramine-treated water (now the majority of U.S. municipal systems) typically degrade noticeably within 3 to 5 years. The AquaPiston canister gasket, made from a chloramine-resistant material, is rated by Kohler for significantly longer service life. Replacement parts are stocked, but the typical homeowner will interact with them far less frequently.
For a full comparison across all top performers, see our guide to TOTO Drake vs Kohler Cimarron and our best Kohler toilets roundup.
Does the AquaPiston Qualify for EPA WaterSense Certification?
Yes. Kohler toilets equipped with the AquaPiston, including the Cimarron, Highline, Wellworth, and Aquia IV, carry EPA WaterSense certification, which requires a maximum flush volume of 1.28 GPF and a minimum MaP score of 350 grams. AquaPiston models far exceed the minimum MaP threshold and use 20 percent less water per flush than the previous 1.6 GPF standard, qualifying them for utility rebates in many U.S. water districts.
EPA WaterSense is the federal certification program modeled on the Energy Star framework. To earn the label, a toilet must use no more than 1.28 gallons per flush (the High Efficiency Toilet threshold), pass third-party MaP testing with a score of at least 350 grams, and meet the performance standards defined in the WaterSense specification for tank-type toilets. The 350 g minimum is deliberately conservative; the program cares about efficiency, not peak performance, and lets MaP scores handle performance signaling independently.
The practical benefit of WaterSense certification beyond environmental responsibility is rebate eligibility. Dozens of U.S. water utilities -- including large programs in California, Texas, and Florida -- offer per-toilet rebates of $50 to $175 for replacing pre-1994 toilets with WaterSense-certified models. Those rebates routinely offset 20 to 50 percent of the purchase price of an AquaPiston toilet, making the efficiency argument a direct financial one for households planning a bathroom renovation.
The AquaPiston's dual-flush variant in the Aquia IV achieves an average flush volume well below 1.28 GPF because liquid-waste flushes use only 0.8 GPF. This makes the Aquia IV eligible for utility programs with dual-flush bonuses, and its average consumption -- based on an industry-standard ratio of 6 liquid flushes to 1 solid flush -- comes in around 0.86 GPF effective average, a meaningful reduction from single-flush designs at 1.28 GPF.
WaterSense-certified toilets are estimated to save the average U.S. household roughly 13,000 gallons of water per year compared to a pre-1994 3.5 GPF toilet, according to EPA published data. For a household of four using a 3.5 GPF toilet installed before the 1994 Energy Policy Act mandates, switching to any 1.28 GPF AquaPiston model represents a reduction of approximately 60 percent in toilet water consumption. At average U.S. water and sewer rates, that translates to roughly $50 to $110 in annual utility savings depending on local pricing.
Which Kohler Toilets Use the AquaPiston, and Which Should You Buy?
Kohler uses the AquaPiston flush valve across most of its mid-range and premium toilet lines, including the Cimarron, Highline, Highline Arc, Wellworth, Memoirs, Santa Rosa, Veil, and Aquia IV dual-flush. The Cimarron and Highline are the most widely recommended for residential use based on their 1,000 g MaP scores, proven long-term reliability, and broad availability of replacement parts. The Aquia IV is the best choice for water-critical regions due to its dual-flush 0.8/1.28 GPF capability.
The Kohler Cimarron is the AquaPiston's flagship expression for general residential use. It is available in both round and elongated bowl configurations, in chair-height (comfort height at 17 to 19 inches from floor to rim) and standard heights, and in two-piece and one-piece forms. The elongated comfort-height two-piece configuration is the most common specification for bathroom remodels. It scores 1,000 g on MaP at 1.28 GPF and is EPA WaterSense certified. Aggregated owner feedback across major retail platforms consistently rates it highly for long-term reliability, seat comfort (with the optional Cachet or Quiet-Close seat), and ease of installation for experienced DIYers.
The Kohler Highline and Highline Arc share the same AquaPiston internals in a slightly different exterior profile. The Highline is a more traditional tank-and-bowl silhouette suited to classic bathroom aesthetics; the Highline Arc has a softened trapway and tank contour. Both perform identically in MaP testing. The Highline is widely available at box-store retailers, making part availability excellent.
The Kohler Wellworth is the entry-level AquaPiston vehicle -- a competent toilet that delivers the same flush performance at a lower purchase cost due to a simpler bowl design and more basic seat. It is the sensible choice for rental properties and secondary bathrooms where aesthetics are not the primary driver. MaP scores remain strong at 1.28 GPF.
For households in drought-prone areas or with high water costs, the Kohler Aquia IV is the most compelling option. Its dual-flush AquaPiston canister delivers 0.8 GPF for liquid waste and 1.28 GPF for solid waste, and the full-flush MaP score hits the 1,000 g ceiling in published test data. The Aquia IV is also available in a wall-hung configuration for bathrooms with concealed in-wall carriers. For a broader look at water-saving toilets, see our dual flush toilets guide.
The Kohler Veil and other one-piece skirted models use AquaPiston in combination with a concealed trapway for a fully smooth exterior. These are premium-priced but offer the easiest cleaning experience because there are no crevices on the trapway exterior. The flush performance is identical to the two-piece Cimarron; buyers are paying for aesthetics and cleaning convenience.
The Memoirs series uses AquaPiston in a traditionally styled tank with architectural detailing -- fluted tank panels and classic proportions -- suited to formal or period-appropriate bathrooms. Again, the underlying flush mechanics are identical. Kohler's consistent deployment of the same valve architecture across its range is a deliberate platform decision: once a technician knows the AquaPiston, every Kohler toilet in the home is serviceable with the same knowledge and parts.
Parts availability is an underrated purchasing criterion for toilets. The Kohler AquaPiston canister, fill valve, and seat components are stocked at major hardware retailers nationwide, and Kohler's parts support line is well-regarded in the plumbing trade. For homeowners or landlords managing multiple properties, the AquaPiston's standardization across models is a significant maintenance convenience compared to managing multiple proprietary flush systems from different brands.
AquaPiston Maintenance: What Actually Needs Attention Over Time?
The AquaPiston's primary maintenance item is the canister seal/gasket. Kohler rates this component for longer service than a typical rubber flapper, particularly in chloramine-treated water systems, but it will eventually require replacement. The symptom is the same as a flapper leak: water running continuously into the bowl (phantom flushing) or the toilet running intermittently as the tank slowly loses level and triggers the fill valve.
Diagnosis is straightforward. Add a few drops of food coloring to the tank and wait 15 minutes without flushing. If color appears in the bowl, the canister seal is leaking. Kohler's replacement canister kits include the full canister assembly and are available at major retailers. Installation requires removing the flush handle chain, lifting the old canister assembly off the valve seat, and pressing the new assembly into position -- a repair that most homeowners can complete without professional help in under 30 minutes.
The fill valve is a separate component from the canister and is the second most likely maintenance item. Kohler uses a tower-style fill valve in most AquaPiston toilets. Replacement fill valves are not proprietary to Kohler; Fluidmaster 400A and equivalent universally compatible valves fit the standard shank threading and are inexpensive. Fill valve replacement is the standard fix for a toilet that runs constantly without a canister leak, fills slowly, or makes noise during fill cycles.
Hard water mineral deposits on the canister seat are a third maintenance consideration in regions with high calcium and magnesium content. Periodic descaling with a diluted white vinegar soak (with the tank drained) prevents the gradual buildup that can prevent the canister from seating fully. This is not an AquaPiston-specific issue; all valve seats in hard-water areas require periodic descaling, but the AquaPiston's smooth plastic seat surface is somewhat easier to clean than the rough ceramic edge of a traditional flapper seat.
For maintenance instructions specific to Kohler's flush mechanisms and for understanding how trapway diameter affects clog frequency, see our toilet trapway size guide.
AquaPiston vs Traditional Flapper: Long-Term Cost Analysis
Comparing the long-term economics of the AquaPiston to traditional flapper systems requires looking at three cost drivers: replacement frequency, water waste from slow leaks, and water efficiency at rated GPF.
Rubber flappers in chloramine-treated water systems typically need replacement every 3 to 5 years in standard service conditions. Each replacement is inexpensive (under $10 for a quality aftermarket flapper), but in a multi-toilet household the aggregated cost and effort across 5 and 10-year periods is non-trivial. More significant is the water loss from a leaking flapper before the homeowner notices: a slow flapper leak losing 30 gallons per day -- a modest and common leak rate -- wastes approximately 10,950 gallons per year, costing $50 to $100 in water and sewer charges depending on local rates.
The AquaPiston gasket replacement is less frequent and the design's resistance to slow leaks (because the canister drops by gravity onto a precision seat rather than relying on rubber buoyancy and flexibility) means the leak-detection window is shorter in practice: when an AquaPiston canister seal fails, it typically fails more definitively and audibly, prompting faster detection and repair versus the gradual silent degradation common in rubber flappers.
At the GPF level, every WaterSense-rated 1.28 GPF AquaPiston toilet saves 0.32 gallons per flush versus a 1.6 GPF toilet. For a household of four using the toilet roughly 20 times daily across all fixtures, that is 6.4 gallons saved per day, or approximately 2,336 gallons per year per toilet -- translating to measurable utility bill reductions that compound across the toilet's 15- to 25-year usable life.
Frequently Asked Questions
What is the Kohler AquaPiston?
The AquaPiston is Kohler's proprietary canister-style flush valve that replaces the traditional rubber flapper. It lifts vertically to open a 360-degree water passage, delivering a symmetrical water surge into the bowl from all sides simultaneously.
How is a canister flush valve different from a flapper?
A flapper is a hinged rubber disc that opens on one side, directing water into the bowl asymmetrically. A canister valve rises straight up from a circular seat, opening all the way around and channeling water evenly from 360 degrees. The canister design reduces reliance on rubber buoyancy and minimizes the chance of incomplete sealing.
What MaP score does the AquaPiston achieve?
Kohler toilets using the AquaPiston, such as the Cimarron and Highline Arc, score 1,000 grams on the MaP flush test at 1.28 GPF. That is the maximum score the protocol measures and represents very high single-flush clearing performance.
Is the AquaPiston EPA WaterSense certified?
Yes. Kohler's AquaPiston toilets including the Cimarron, Highline, Wellworth, and Aquia IV carry EPA WaterSense certification, confirming they use no more than 1.28 gallons per flush and have passed independent MaP performance testing at or above the minimum 350 g threshold.
How often does the AquaPiston canister seal need to be replaced?
Kohler states the AquaPiston canister is designed to outlast rubber flappers, particularly in chloramine-treated water. Real-world owner experience and plumber feedback suggest replacement intervals of 7 to 12 years or more in typical conditions, compared to 3 to 5 years for rubber flappers in the same water chemistry.
Can I replace the AquaPiston canister myself?
Yes. The canister is designed for DIY replacement. The process involves draining the tank, disconnecting the lift chain, lifting the old canister assembly off the valve seat, and pressing the replacement into position. Kohler's replacement kits are widely available at major hardware retailers, and the repair typically takes 20 to 30 minutes without specialized tools.
What Kohler toilets come with the AquaPiston?
The Cimarron, Highline, Highline Arc, Wellworth, Memoirs, Santa Rosa, Veil, and Aquia IV all use AquaPiston technology. The mechanism is standard across Kohler's gravity-fed residential line, making parts and service knowledge transferable across models.
Is the AquaPiston the same as the Class Five flush system?
Not exactly. Class Five is Kohler's broader performance designation for high-efficiency flush systems. AquaPiston specifically refers to the canister valve design. Most Class Five toilets use an AquaPiston valve, but the terms describe slightly different aspects: AquaPiston is the hardware; Class Five refers to the system's performance tier.
How does the AquaPiston compare to TOTO's G-Max?
Both achieve 1,000 g MaP scores at 1.28 GPF and carry WaterSense certification. G-Max uses a 3-inch flapper and a large siphon jet on a deeply glazed straight trapway. AquaPiston uses a 360-degree canister valve. G-Max parts are universally stocked and inexpensive; AquaPiston parts have good availability but are Kohler-specific. Both are excellent long-term performers.
Does the AquaPiston work in dual-flush toilets?
Yes. The Kohler Aquia IV and certain other models use a dual-flush variant of the AquaPiston. The canister has two lift positions: a partial lift for 0.8 GPF liquid-waste flushes and a full lift for 1.28 GPF solid-waste flushes. The same 360-degree opening geometry applies at both positions.
What is the trapway diameter on AquaPiston toilets?
Trapway diameter varies by model rather than by valve type. The Kohler Cimarron has a 2-1/8-inch fully glazed trapway, which is standard for the category. The AquaPiston valve is compatible with various trapway sizes; the two are engineered independently. Larger trapway diameters reduce clog risk, and Kohler's glazed passageways help waste move through smoothly.
Can the AquaPiston develop slow leaks?
Yes, though less commonly than rubber flappers. If the canister gasket degrades or hard-water mineral deposits accumulate on the valve seat, the canister may not fully close, causing a slow leak from tank to bowl. The food-coloring dye test diagnoses this. When it does fail, the failure tends to be more noticeable than a typical flapper leak because the canister drops by gravity and does not partially seal in the way a softened flapper can.
Does hard water damage the AquaPiston?
Mineral deposits can accumulate on the canister seat in hard-water areas, potentially preventing a full seal over time. Periodic maintenance with diluted white vinegar (draining the tank and soaking the valve seat) is effective preventive care. Kohler's plastic canister seat is less affected by mineral scaling than ceramic surfaces.
What is the warranty on Kohler AquaPiston toilets?
Kohler offers a limited lifetime warranty on the vitreous china toilet body and a one-year warranty on mechanical components including the AquaPiston flush valve, fill valve, and other tank trim parts against defects in materials and workmanship. Extended coverage and specific terms should be verified directly with Kohler or the retailer at the time of purchase.
Is the AquaPiston available in pressure-assist versions?
The standard AquaPiston is a gravity-feed design. Kohler does not widely offer pressure-assist versions of its AquaPiston lineup for residential use. Pressure-assist technology from manufacturers like Sloan and Flushmate uses compressed air to supplement gravity and is found in a separate product segment from the AquaPiston.
How does the AquaPiston affect bowl cleaning?
The 360-degree water entry at the start of a flush contributes to better rim-hole coverage and a more thorough bowl rinse compared to single-axis flapper flush entry. However, bowl cleaning performance is also heavily influenced by rim-hole design, bowl geometry, and whether the toilet has a rimless or under-rim design -- factors specific to individual models rather than the AquaPiston valve alone.
What is the difference between AquaPiston and AquaPiston Canister?
Kohler has used both names interchangeably in its marketing and product documentation. Both terms describe the same canister valve technology. Some Kohler materials say "AquaPiston Canister" to emphasize the physical form factor; newer materials may say simply "AquaPiston." There is no functional difference between toilets labeled with one term versus the other.
Will the AquaPiston fit as a replacement in a non-Kohler toilet?
No. The AquaPiston is a proprietary Kohler component designed to fit Kohler's specific tank geometry and valve seat dimensions. It is not a universal retrofit part. If you want AquaPiston performance in a bathroom currently using another brand's toilet, the practical solution is to install a Kohler toilet rather than attempting a cross-brand valve replacement.
Is the Kohler Cimarron the best AquaPiston toilet for most households?
The Cimarron is the most commonly recommended AquaPiston toilet for general residential use, based on its 1,000 g MaP score, WaterSense certification, broad model availability, and strong aggregated owner satisfaction. It is available in most standard rough-in dimensions (12-inch standard; 10-inch and 14-inch available for non-standard installations), elongated and round bowl shapes, and two-piece and one-piece forms.