Top flush dual control toilet, Akaroa New Zealand (C) Daniel Friedman Pressure-Assisted & Reservoir Barrier Water Saving Toilets
Low-Water-Usage & Power-Assist Toilet Designs Brands, Features & Sources

  • LOW WATER USAGE TOILETS - CONTENTS: pressure-assisted or "power flush" water saving toilets, toilet designs, functions, properties, features, & identifying photographs including FLUSHMATE TOILETS and other power-assisted flush water conserving toilets that use vacuum assist flush methods, air pressure assist toilet flush designs, or other pressure boosted toilet flush mechanisms.
  • POST a QUESTION or READ FAQs about properties, features, & identifying photographs of top flush & dual flush toilets
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Power assisted flush water saving toilets:

This article describes low water consumption toilets that use special design features ranging from simple reduced flush water volume to power-assisted-flush toilets using the Flushmate™ design. Here we describe the operation and sources of power-assisted flush toilets using vacuum-assisted flush, air pressure assisted flush, or other pressure-boosted toilet flush mechanisms.

We give typical water flush volume quantities for different types of toilets and we explain how power-assisted flush toilets work. This article also gives information about the Flushmate III Series 503 toilet safety recall notice.

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Low Water Consumption Toilets - Water Saving Toilets

Water saving toilet using internal reservoir (C) Daniel FriedmanApproaches to Water-Conserving Toilet Designs

Water saving toilets use one or more of several strategies to reduce the volume of water used in flushing away waste

Typical toilet water flush volumes for various toilet types & designs

The water volume used in each toilet flush varies quite a bit, and flush volume will vary by flush type for dual flush toilets. Also the nominal flush volume for toilets may not accurately describe an individual toilet unit depending on how the toilet fill valve has been adjusted.

Air & Water Powered Flush Toilets (Pressure Assist): the Sloan Flushmate

Sloan Flushmate power flush toilet tank & controls (C) Daniel FriedmanAir-powered pressure-assist flush toilets: if when you flush a top-flush-control toilet the fixture flushes with a rather stunning WHOOSH! that leaves you glad you didn't drop your wallet into the toilet, it's probably a power flush toilet such as the Sloan Flushmate. Sloan Flushmate® toilets: power-flush system reduces water use.

Power flush toilet model shown in our photo below: Sloan Flushmate® Model M-101526-F3 using a 1.6 gpf or 6LPF toilet flush volume. Other Flushmate® toilet models (Flushmate IV) use less than 1 gallon per flush.

The FLUSHMATE® system traps air and as it fills with water, it uses the water supply line pressure to compress the trapped air inside.

The compressed air is what forces the water into the bowl, so instead of the “pulling” or siphon action of a gravity unit, the pressure-assist unit “pushes” waste out. This vigorous flushing action cleans the bowl better than gravity units. - quoted from, retrieved 2/2/2014

The manufacturer points out that the increased pushing action provided by the air-powered Flushmate® design combines the advantage of reduced flush water volume with improved drain-carry performance: that is, solid waste that would be carried along a typical sewer line for a distance of 40 feet (12 meters) to comply with ANSI standard requirements will in the Flushmate® design be carried for 60 feet (18 meters) - a 50% improvement over a standard gravity-operated toilet flush tank. - APSE Research Report 91-01 & Standards: ANSI/ASME A112.19.2M and CSA B-45

Sloan Flushmate(R) toilet flush trapway details, adapted from Sloan www.flushmate.comNote: the Flushmate® toilet design is apparently not suitable for a retrofit to existing toilets.

Image at left adapted from Sloan Flushmate literature. (On this particular toilet bowl the water comes down from the front of the rim to the jet (red arrows.) - image used courtesy of Sloan Flushmate ® with permission 2/4/14

The company points out that their toilets use an "advanced bowl design" described as follows:

FLUSHMATE®-equipped bowls are hydraulically designed to “push” contents out of the trapway instead of gravity siphoning. Siphoning requires a more complicated trapway, impeding performance.

FLUSHMATE'S trapway is simple, only needing one bend. FLUSHMATE®-equipped water closets eliminate the need to double flush because the trapway design has fewer bends. Toilets with FLUSHMATE® use a siphon-jet bowl to meet and exceed ANSI/ASME A112.19.2M and CSA B-45 performance requirements.

FLUSHMATE®-equipped water closets have trapways that are specifically designed to allow waste to be extracted earlier in the flush, unlike gravity trapways, which require a choke area or siphon bend that ultimately restricts flow. - quoted from, retrieved 2/2/2014

Excessive Flush Noise, Splash, Power Flush Toilet Repairs: Causes & Cures

Question: bubbles in lower floor toilet after installing water saving toilet upstairs

(June 7, 2016) Mary said:
We installed a new water saving toilet upstairs and now the toilet on the 1st floor is acting like a huge bubbler system every time we flush. Using a hose, we poured water down the vent stack on the roof and no water back up. Then we poured water down the sewer line and no back up. Then we flushed the 2nd floor toilet with the sewer drain left open there was zero splashing. We are at a loss as to what to try next. Any ideas?


Typically those conditions mean that the toilet(s) are not venting adequately or there is a drain blockage downstream from the lower floor toilet.

Your tests were a good place to start, but I'm not sure that the water-pour test will tell us if a toilet is too far from or inadequately vented; rather you're simply finding that the vent system - whatever it is and wherever it's routed - isn't blocked.

Your second test was brilliant - thank you. To me your test suggests that the 2nd floor toilet is either not connected to a vent at all or is too far or the vent is inadequate.

Hmmm. This was a new toilet, but it replaced an older one, right? And am I right that you never saw this problem with the prior toilet?

If yes, and yes,
I suspect that the new toilet, in order to flush with less total water volume, is perhaps flushing faster, more aggressively, perhaps you're even using a toilet that gives an air shot to help the flush process? IF so that may be showing an underlying vent inadequacy. And air in the power flush may be showing up in that lower floor toilet bowl if, as I suspect, there ius also a partly blocked drain or vent.

I'll give it more thought. Let me know what you find.

(June 8, 2016) Mary said:
Had the sewer line cleaned out (found tree roots) and now the problem is solved. :)

(June 9, 2016) Mary said:
Well, scratch that for a fix. When we checked it yesterday after the clean out, the cover for the vent was not put back on(discovered that this morning). Only other thing we can think to do is put an old style toilet back in. Will let you know

(mod) said:
It's true that some toilets don't flush well; but there are certainly power-assisted low-water-usage or low-flush toilets that are very aggressive and clean-flushing; check those out.

FYI cleaning out tree roots is a short term fix - the roots will return as will blockages from collapsing pipe damaged by the roots or by other causes. Did you have the whole line scoped? Is this on a private septic that could be backing up?

Question: How do you stop your toilet from splashing after flushing the toilet?

(Feb 24, 2016) Rick Moore said:
How do you stop your toilet from splashing after flushing the toilet?


I'm not sure, Rick. If the toilet has always splashed I think it may be an artifact of the bowl design.

You could check that the toilet tank level is filled to the fill line marked in the tank.

Beyond that you'd have to experiment with different flush valve designs.

If your toilet is a power-flush or power-assisted flush model, then see the Q&As below.

Question: after flushing toilet water backsplashes from bowl

(Apr 9, 2016) dave said:

after flushing toilet water backsplashes from bowl, tub and sink do not seem to have a problem. problem started after a clogged toilet incident that I plunged away. for the most part toilet flushes normally except for the powerful backsplash after every flush. there has been an occasional slow flush reported


Check the toilet fill level - if too full

Check for slow drainage or gurgling at other drains when flushed; I suspect the blockage is not fully removed.

If your toilet is a power-flush or power-assisted flush model, see the Q&As just below

Question: water conservation toilet splashes fecal matter when flushed

2016/10/10 MetalTiger said:

Ever since we had "water conservation" toilets installed every flushing throws fecal matter up onto the underside of the toilet lid. I am sick of cleaning this off.

Guests of course wouldn't know to do this so the next person sitting down is actually resting their back against dried fecal matter. How do I fix this? I mentioned it to a plumber once and his response was "...a lot of people complain about that.." Hello??!

Is there a fix? Thanks.

This question was posted originally at TOILETS, INSPECT, INSTALL, REPAIR

Reply: Repairs for wild too-strong power-flush toilet splash-up

Good question, Tiger.

Fixing a splashing or too-strong power-flush type toilet:

Power-flush toilets can misbehave in ways similar to conventional flush toilets: e.g. running, or a weak flush. those troubles are typically fixed by adjustment and cleaning, for example you may need to clean the intake screen on the water supply assembly.

A Sloan flushmate toilet that runs may be caused by insufficient water pressure to the toilet or simply misadjustment of the actuator flush rod or push-button. A clogged inlet screen can cause the same troubles as low water pressure.


Excessive power in a power-flush toilet can splash sewage so unpleasantly that it can drive users back to the outhouse.

The trouble may be simply one of adjustment of the power flush system, or it may require cleaning or repair of the air regulator.

  1. First: check the water level in the toilet bowl after the toilet has been flushed and the flush-tank refill cycle has completed.

    . If the toilet bowl water level is too high that can cause splashing. Some flush systems allow adjustment of the bowl fill level, some by a simple plastic squeeze valve mounted on (or added onto) the plastic tube conducting water to the toilet bowl during toilet tank refill.
  2. Next: check for an obstruction, crud, debris blocking the front of the toilet bowl = a source of splash-up. (and unlikely IMO)
  3. Next: check the building water pressure level and compare that with the operating range specified by your power flush toilet brand and model.

    Typical building water pressure is between 20 psi and 70 psi. Much higher pressure is going to cause trouble at fixtures: leaks and of course wasted water.

    Send me (page bottom CONTACT) a photo of the toilet, its flush mechanism, labeling, model name and I can help research this for you.
    If the incoming water pressure is too high you will need to install a pressure regulator to drop it back. Just closing a supply valve part way won't fix the trouble.
  4. Next: check for mineral or crud clogging the water holes around the toilet rim. During a toilet flush water directed out of the bowl rim is designed to clean the bowl and to assist the flush.

    But if the holes are clogged too much water may be directed through other holes or through the primary water supply path causing ugly splashing or a "too-strong toilet flush" that is downright violent.

A newly-installed Flushmate type toilet probably won't have rim hole clogs. In that case, since the pressurizing system is set at the factory and is not user adjustable, you're left with installing a whole-house pressure regulator OR a pressure regulator on a water line supplying jut the toilet Set that output pressure down to closer to the minimum operating pressure of the power flush toilet, typically 20-30 psi.

Let us know how that works for you.

Last: replace the toilet. Some power flush toilets suffered from such bad behavior that they were recalled.

Joe Barrett reported on this in the Wall Street Journal (Barrett, Joe, "High-Pressure Toilets Shake Up Bathrooms" The Wall Street Journal, Dec. 18, 2002), noting that pressure assist flush toilets were particularly noisy and troublesome.

A Kohler power flush toilet model actually could break (talk about dangerous!) and was recalled. Later power-flush toilet models should have corrected the worst of these problems. Also see the Flushmate toilet recall notice below.

On 2016-09-10 by Richard Baldwin - When the toilet was flushed, there was a"wooshing" sound like air pressure. It was similar to the sound of toilets on cruise ships.

Hope you can help. Approximately eleven years ago we were remodeling two of our bathrooms.

At the suggestionn of the installer, we opted for type of aparatus in the tank I had never seen. There was no visible water in the tank, and instead, there was a rather large stainless steel tank which appeared to be a pressuse tank.

When the toilet was flushed, there was a"wooshing" sound like air pressure. It was similar to the sound of toilets on cruise ships.

It was very efficient and I would like to have one installled in our current home. The installer is deceased and I cannot recall the type or brand. I do recall the cost was approximately one one hundred dollars more than a mid level convential toilet. Can you help?

This question was posted originally at WATER TANK: USES, TROUBLESHOOTING

On 2016-09-10 by (mod) - pressure-assisted flush toilet noises

Richard this sounds like a pressure-assisted flush toilet that uses a combination of building water pressure and an air charge to flush the toilet bowl while using less water than some other systems.

Searching InspectApedia for Power Assist or Pressure Assist Toilets finds the most detail about these at

There I use the "Air & Water Powered Flush Toilets (Pressure Assist): the Sloan Flushmate" as an example.

At I also describe this as "Pressure-assist flush toilet: the toilet is flushed by water that is given a velocity boost by a pressure system using a pump,compressed, air, or other means. Typically pressure-assist toilet designs are found on water-saving low-flush-volume toilets."

Our home page for power assisted flush toilets is this article LOW WATER USAGE TOILETS

Pressure assist or "power assisted flush" toilets are also described in a bit more detail at TOILET DESIGN CHOICES

For details about air, water pressure or other assisted-flush or power-flush toilets see LOW WATER USAGE TOILETS or go directly to FLUSHMATE TOILETS (within that article) where we discuss power-assisted flush toilets that also conserve water.

We also discuss power flush toilets also at TOILETS REPAIR FAQs

Flushmate III Series 503 Toilet Safety Recall Notice

Flushmate Series III Toilet Safety Recall Notice - at InspectApedia.comWatch out: The Flushmate III toilet was subject to a safety recall notice. If you have a Flushmate III toilet that was manufactured between October 14, 1997 and April 30 2011, the recall notice applies, and a repair kit should be installed.

[Click to enlarge any image]

The Flushmate toilet safety recall notice also states that:

The affected FLUSHMATE III Series 503 Units can burst at or near the vessel weld seam releasing stored pressure. This pressure can lift the tank lid and shatter the tank, posing impact or laceration hazards to consumers or property damage.

Even if you have installed repair kits on some of your Flushmate III units, please verify the remaining serial numbers to ensure that a rpair kit is installed on all affected Flushmate III units.

For your safety, we are sending this postcard [sic] to all registered owners and we are asking you to check your serial numbers as soon as possible, even if you are receiving this notice again. SEE OTHER SIDE [of the post card] FOR DETAILS.

Contact the company by telephone at 1-800-303-5123.

Also see

You can also contact Flushmate at 30075 Research Drive, New Hudson MI 48165.


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