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Quick answer from a licensed plumber: Buy the Kohler Highline Pressure Lite K-3519 for most homes. Kohler lists it at 1.0 gallon per flush with a Sloan Flushmate vessel and a 2-1/4 in. trapway, but it needs at least 35 psi of static water pressure. If your static pressure is under 35 psi but at least 20, the Kohler K-3493-RA at 1.6 gallons. For a standard-height bowl, the Kohler Wellworth K-3531. If your pressure-assist toilet already runs on or will not charge, a new Flushmate vessel may fix it without replacing the toilet.
Our pick for most homes: the Kohler Highline Pressure Lite K-3519, with a 1.0 gpf Flushmate flush and a 2-1/4 in. trapway. Check the Kohler Highline Pressure Lite K-3519 on Amazon
A pressure-assist toilet uses your water pressure, not just the weight of the water in the tank, to push waste down the drain. That makes it the toilet plumbers reach for when a house has a long or old drain line, or a toilet that clogs no matter what. It is not for every house: it needs enough supply pressure, it is louder than a gravity toilet, and its parts are specific. This page covers only pressure-assist toilets, the replacement vessel if yours already has one, and how to tell whether your house suits one. Our best toilet guide covers gravity toilets.
Pressure-Assist Toilets Compared
| Toilet | Flush | Seat height | Trapway | Min. static pressure (Kohler) | Lever |
|---|---|---|---|---|---|
| Kohler Highline Pressure Lite K-3519 | 1.0 gpf, WaterSense | Comfort Height (K-3519-RA sheet; same K-4304 bowl as the K-3493), 31-1/4 in. overall | 2-1/4 in. glazed (2-3/16 in. passageway on Kohler’s 2024 sheet) | 35 psi | Left (RA = right) |
| Kohler Highline Classic K-3493-RA | 1.6 gpf | Comfort Height | 2-1/4 in. glazed (2-3/16 in. passageway on Kohler’s 2024 sheet) | 20 psi | Right |
| Kohler Wellworth Pressure Lite K-3531 | 1.0 gpf (Kohler sheet), WaterSense | K-4303 bowl, not listed as Comfort Height, 29-3/4 in. overall | 2-1/4 in. | 35 psi | Left |
From the Kohler specification sheets linked below, read on October 2, 2026. All three use a Sloan Flushmate vessel and a 12 in. rough-in. Every linked toilet listing was in stock that day. Amazon.com sold the K-3519, K-3519-RA and K-3531; the K-3493-RA buy box showed a third-party seller, so check the seller before you buy.
How a Pressure-Assist Toilet Works
A gravity toilet lets the tank water fall into the bowl and relies on that rush to start a siphon. A pressure-assist toilet has a sealed plastic vessel inside the china tank. Flushmate, which makes the vessel in all of the Kohler picks here, says the vessel traps air, and as it fills, the supply-line pressure compresses that air. When you push the lever, the compressed air forces the water into the bowl. Flushmate says its systems reach up to 70 gallons per minute peak flow, and that they carry waste up to 60 feet down a drain line against the 40 feet the best gravity toilets meet. Those are Flushmate’s figures, not ours.
Flushmate’s owner guide lists the parts: a lower supply group with an inlet screen, a pressure regulator with a back check and a relief valve; an upper supply group with an air inducer and a vacuum breaker; a flush valve cartridge with an adjustable actuator; and the vessel itself, with a name plate carrying the serial number. Flushmate says the sealed vessel does away with the flapper and fill valve leaks that gravity toilets get.
Is a Pressure-Assist Toilet Right for Your House?
Check your water pressure first
This decides it. Kohler asks for at least 35 psi static pressure on its 1.0 gpf Pressure Lite toilets and 20 psi on the 1.6 gpf Highline Classic, and 80 psi maximum on all of them. Static means with nothing running. A hose-bib pressure gauge gives you the number in a minute. If you are on a well, your pressure switch setting is your range; see well pressure switch 30/50 vs 40/60. A 30/50 switch lets pressure fall to 30 psi before the pump kicks on, under the 35 psi Kohler asks for (our arithmetic), which is a reason to look at the 20 psi K-3493 or keep a gravity toilet. Over 80 psi, fix the pressure first with a pressure reducing valve.
Good reasons to choose one
- A toilet that keeps clogging after you have ruled out the drain. Start with why a toilet keeps clogging.
- A long or old drain line. Gerber says its Flushmate-powered Ultra Flush toilets “may be used in applications where old iron pipes are installed,” and a Sloan product line manager, interviewed on Flushmate’s blog, lists drain line carry first among three advantages over low-flow gravity toilets, especially in older buildings.
- Less water per flush with a strong push. The Kohler K-3519 and K-3531 use 1.0 gallon.
Reasons to skip one
- Low or swinging water pressure under the toilet’s minimum.
- Noise. The flush is a loud, short burst. Even Flushmate says these toilets are sometimes perceived as louder.
- Hot or tempered water at the toilet. Flushmate says its systems are for cold potable water only, and hot or non-potable water voids the warranty.
- You use in-tank cleaner tablets. Flushmate says bleach, drop-in blocks or tablets in the china tank void its warranty.
- A short warranty. Kohler lists a one-year limited warranty on all three picks.
Rough-in and seat height
All three Kohler picks are 12 in. rough-in toilets. Measure from the finished wall to the center of the closet bolts; our rough-in guide shows how. For seat height, Kohler’s component lists put the same K-4304 bowl on the K-3519 and the K-3493, and Kohler’s 2024 sheets for the K-3519-RA and the K-3493 both list Comfort Height (chair-height seating). The Wellworth K-3531 uses the K-4303 bowl and stands 1-1/2 in. lower overall on Kohler’s drawings (our arithmetic). Comfort height vs standard toilets explains who each suits.
Kohler Highline Pressure Lite K-3519 (1.0 gpf)
1.0 gpf, EPA WaterSense · Sloan Flushmate pressure vessel · 2-1/4 in. glazed trapway · 11-1/2 x 9-1/2 in. water area · 12 in. rough-in · elongated two-piece · 31-1/4 in. tall overall · 35 to 80 psi static supply, per Kohler · seat and supply line sold separately · one-year Kohler limited warranty
This is the pressure-assist toilet to buy for most homes. Kohler lists it at 1.0 gallon per flush with a Sloan Flushmate vessel inside the china tank, a 2-1/4 in. glazed trapway and an 11-1/2 by 9-1/2 in. water area. The sheet lists EPA WaterSense, and Kohler’s specification says it will comply with the 2010 ADA standards when installed per Section 604. It uses the same K-4484 tank as the Wellworth below, which matters later: Flushmate sells a replacement system made for that tank.
The one number to check before you buy is pressure. Kohler’s sheet asks for at least 35 psi static pressure and no more than 80 psi. That is higher than the 20 to 25 psi Flushmate lists for its vessels alone, so go by Kohler’s figure for this toilet. The linked listing has the trip lever on the left. If your tank sits where a right-hand lever is easier to reach, Kohler makes the K-3519-RA with a right-hand lever. Kohler covers it with a one-year limited warranty.
- 1.0 gallon per flush with a Flushmate vessel
- 2-1/4 in. glazed trapway
- WaterSense listed on Kohler’s sheet
- Right-hand lever version sold too
- Needs at least 35 psi static, per Kohler
- One-year Kohler limited warranty
- Seat and supply line sold separately
- Louder flush than a gravity toilet
Verdict: The pressure-assist toilet to buy for most homes with good water pressure: 1.0 gallon, a wide trapway and a Flushmate vessel you can replace later.
Kohler Highline Classic K-3493-RA Comfort Height (1.6 gpf)
1.6 gpf · Pressure Lite flush with a Sloan Flushmate vessel · Comfort Height (chair height) · 2-1/4 in. glazed trapway (2-3/16 in. passageway on Kohler’s 2024 sheets) · 12 x 10 in. water area · 12 in. rough-in · right-hand trip lever · 20 to 80 psi static supply, per Kohler · seat and supply line sold separately · one-year Kohler limited warranty
If your water pressure sits between 20 and 35 psi, this is the Kohler pressure-assist model to look at. Kohler asks for only 20 psi static minimum and 80 psi maximum, against 35 psi for the 1.0 gpf models. Like the K-3519, it uses Kohler’s K-4304 Comfort Height bowl, which Kohler says “offers chair-height seating that makes sitting down and standing up easier for most adults,” and it has a 12 by 10 in. water area, the largest of the three Kohler picks.
The trade-off is water. It uses 1.6 gallons per flush, and Kohler’s K-3493 sheets list the Energy Policy Act of 1992 but not EPA WaterSense, which the 1.0 gpf models carry. Some states and towns limit new toilets to 1.28 gallons, so check your local code before you order this one. The linked listing is the right-hand lever version in white; its buy box showed a third-party seller when we checked, so confirm the seller before you order. Kohler’s base K-3493 has a left-hand lever; we did not link it because the Amazon listing we found labels it 1.4 gpf, which does not match Kohler’s 1.6 gpf sheet.
- Comfort Height chair-height bowl
- Lowest pressure need of the Kohler picks: 20 psi
- Largest water area here, 12 x 10 in.
- Flushmate vessel, same as the others
- 1.6 gallons per flush, no WaterSense on Kohler’s sheet
- May not meet a 1.28 gpf local limit
- Linked listing is right-hand lever only
- One-year Kohler limited warranty
Verdict: The pick where water pressure runs between 20 and 35 psi, if your code allows 1.6 gallons.
Kohler Wellworth Pressure Lite K-3531 (1.0 gpf)
1.0 gpf on Kohler’s sheet, EPA WaterSense · Sloan Flushmate pressure vessel · 2-1/4 in. trap passageway · 11-1/2 x 9-1/2 in. water area · 12 in. rough-in · 29-3/4 in. tall overall · 35 to 80 psi static supply, per Kohler · seat and supply line sold separately · one-year Kohler limited warranty
The Wellworth Pressure Lite shares the Highline’s K-4484 tank, 1.0 gpf flush, 2-1/4 in. trap passageway and 35 psi minimum. The difference is the bowl. Kohler lists a different bowl, the K-4303, does not list Comfort Height on it, and draws the Wellworth at 29-3/4 in. tall overall against the Highline’s 31-1/4 in. Kohler lists it as EPA WaterSense and as meeting California Energy Commission rules.
One thing to check on arrival: the Amazon title calls this a 1.1 gpf toilet, while both Kohler sheets for the K-3531 say 1.0 gpf. We go by Kohler’s sheet, but read the tank label before you install it if the gallons matter for your local code. Kohler also makes a K-3531-T with tank cover locks for rentals and public restrooms. Its current sheet lists biscuit and black only, so we linked the white K-3531.
- Same 1.0 gpf Flushmate tank as the Highline
- Lower overall height than the Highline
- WaterSense and California Energy Commission listed
- Uses the same F43 replacement system
- Amazon title says 1.1 gpf; Kohler says 1.0
- Needs at least 35 psi static, per Kohler
- Seat and supply line sold separately
- One-year Kohler limited warranty
Verdict: The Highline’s 1.0 gpf flush on Kohler’s lower K-4303 bowl.
Flushmate M-101526-F43 Replacement System (1.0 gpf, Kohler K-4484 tank)
Genuine Flushmate replacement vessel · 1.0 gpf · listed to fit the Kohler K-4484 tank · replaces Flushmate 504 series and Series III systems, per the listing · gaskets and seals included, per the listing · 25 psi minimum for the 504 vessel, 80 psi maximum, per Flushmate · sold by Flushmate’s maker store (Sloan Marketplace)
If you already have a Kohler Pressure Lite and it runs on, leaks inside the tank or will not charge, you may not need a new toilet. Flushmate sells the vessel by itself. This F43 system is listed to fit the Kohler K-4484 tank, the tank Kohler’s sheets put on both the Highline K-3519 and the Wellworth K-3531. The listing calls it an official replacement for Flushmate’s 504 series, and Flushmate’s owner guide lists the 504 at a 25 psi minimum and 80 psi maximum for the vessel.
For other brands, match the old vessel first. Flushmate’s guide shows a name plate with the serial number on the vessel, and Flushmate sells the 1.6 gpf M-101526-F31 system, which its listing calls a replacement for 503 series and Series III systems and says fits most OEM tanks. Read the plate and use Flushmate’s part finder before you order. Before you replace anything, try the three fixes Flushmate lists for a run-on: re-check the cartridge actuator adjustment, clean the inlet screen in the supply shank and check your supply pressure, and remove, rinse and reinstall the flush cartridge.
- Rebuilds a Kohler Pressure Lite without pulling the toilet
- Genuine Flushmate part from Flushmate’s store
- Gaskets and seals included, per the listing
- 1.6 gpf F31 version for 503 series tanks
- Only for Flushmate-equipped toilets
- Must match the tank and series; check the name plate
- Sold by Flushmate’s store, not Amazon.com
- Inside-the-tank work: shut off and drain first
Verdict: Before you replace a Kohler Pressure Lite, check whether a new Flushmate vessel fixes it.
I send an occasional note when a new guide goes up — repairs worth doing yourself, and the parts that actually last. No spam, no course funnel; written by a licensed Georgia plumber.
Living With a Pressure-Assist Toilet
Flushmate’s guide says you may need to flush a new toilet a few times to fully charge the system. After that, the routine is short. Clean the bowl and the outside of the tank as you would any toilet, and keep chlorine, bleach, drop-in tablets and disinfectants out of the china tank, which Flushmate says void its warranty. If the toilet runs on after a flush, Flushmate’s steps are: re-check the cartridge actuator adjustment, clean the inlet screen in the supply shank and check your supply pressure, then remove, rinse and reinstall the flush cartridge. If it leaks between the tank and bowl, Flushmate sends you to the toilet maker’s instructions; that is the same tank-to-bowl seal job as any two-piece toilet.
When the vessel itself fails, you can usually replace it without replacing the china. Read the name plate on the vessel and order the matching Flushmate system. Flushmate’s site also lists recall notices for the Flushmate II 501-B and Flushmate III, so check your vessel’s name plate against them.
Before You Buy
- Measure static water pressure. 35 psi or more for the 1.0 gpf Kohler models; 20 psi or more for the K-3493; under 80 psi for all.
- Measure the rough-in. All three picks are 12 in.
- Check your local flush limit. The 1.0 gpf models carry WaterSense on Kohler’s sheets; the 1.6 gpf K-3493 may not be allowed where new toilets are limited to 1.28 gallons.
- Pick the lever side. Look at where your tank sits against the wall or vanity.
- Count the parts you still need. All three need a seat, a supply line and a wax ring.
Installing a Pressure-Assist Toilet
The swap is the same as any two-piece toilet: shut off the water, drain the tank and bowl, pull the old toilet, clean the flange, set a new wax ring and bolt the bowl down. See how to replace a toilet for the full steps. Flushmate’s guide adds one thing: flush the supply lines before you connect the toilet, and adjust the cartridge actuator after the vessel is fully charged. Kohler’s sheets say back-to-back toilets on one stack need a 45° double wye fitting, not a double sanitary tee. If your pressure is too high or too low, or the drain line behind the wall is the real problem, that is a job for a licensed plumber.
FAQ
How does a pressure-assist toilet work?
A sealed vessel sits inside the china tank. Flushmate says the vessel traps air, and as it fills, your supply-line pressure compresses that air. When you flush, the compressed air forces the water into the bowl, so the toilet pushes waste out instead of relying only on the siphon a gravity toilet uses.
Are pressure-assist toilets loud?
Louder than gravity toilets, yes. A Sloan product line manager, interviewed on Flushmate’s blog, says they are “sometimes perceived as louder” and that newer models reduce the flush sound. The flush is a short burst, and Flushmate says there is no long refill hiss afterward. If the toilet is next to a bedroom, keep that in mind.
What water pressure does a pressure-assist toilet need?
Go by the toilet’s sheet. Kohler lists 35 psi minimum static pressure for the 1.0 gpf Highline K-3519 and Wellworth K-3531 and 20 psi for the 1.6 gpf Highline Classic K-3493. Flushmate lists 20 psi for its 503 vessels and 25 psi for the 504, for the vessel alone, and 80 psi maximum for all of them. Check your house with a water pressure gauge on a hose bib first.
Can I use in-tank cleaner tablets in a pressure-assist toilet?
No. Flushmate’s owner guide says chlorine products such as household bleach, drop-in blocks or tablets, or disinfectants applied inside the china tank void the Flushmate warranty. Clean the bowl and the outside of the tank the normal way.
Can I turn my gravity toilet into a pressure-assist toilet?
Not with the vessels on this page. Flushmate’s replacement systems are listed for toilets that already have a Flushmate vessel and a tank made for it. If you have a gravity toilet that clogs, the answer is a new pressure-assist toilet or a stronger gravity model from our best toilet guide.
Why Trust Plumbing Picks
Plumbing Picks is written by a licensed Georgia journeyman plumber. Every spec here comes from the maker documents linked below or from the Amazon listings we link; nothing comes from hands-on testing. On October 2, 2026, every linked listing was in stock. Amazon.com sold the K-3519, K-3519-RA and K-3531, the K-3493-RA buy box showed a third-party seller, and the Flushmate systems were sold by Sloan Marketplace, Sloan’s own Amazon store (Kohler’s sheets credit FLUSHMATE to Sloan Valve Company). If you buy through a link we may earn a commission at no extra cost to you. Nobody pays to be included here. More on who writes this and how we pick.
Sources
- Kohler: Highline Pressure Lite K-3519 specification sheet, K-3519 specification 1054185-4, K-3519-RA sheet
- Kohler: Highline Classic K-3493-RA specification sheet, K-3493 sheet
- Kohler: Wellworth Classic K-3531 specification sheet, Wellworth Pressure Lite K-3531 sheet
- Flushmate: Owner Guide, 503, 503-H, 503UH and 504 series, Flushmate III 503 series page
- Flushmate: What are pressure-assisted toilets, Flushmate: Pressure-assist vs. gravity (Sloan interview), Flushmate: homes or businesses
- Gerber: Ultra Flush pressure-assist catalog pages
- Amazon listings for the Kohler K-3519, K-3519-RA, K-3493-RA and K-3531 and the Flushmate M-101526-F43 and F31 systems (linked above)
Bottom Line
A pressure-assist toilet pushes waste farther down a house drain than a gravity toilet, by Flushmate’s figures, as long as the house has the water pressure for it and you can live with the noise. The Kohler Highline Pressure Lite K-3519 is the one to buy for most homes. The K-3493-RA drops the pressure minimum to 20 psi at 1.6 gallons, and the Wellworth K-3531 is the standard-height version of the 1.0 gpf flush. Measure your static pressure before you order, and if your current pressure-assist toilet acts up, check the Flushmate vessel before you replace the china.