What is a pressure assist toilet?

A pressure-assisted toilet—also known as a power flush toilet—contains a sealed pressure tank that houses air and water. The vessel traps air, and as it fills with water, it uses the water supply line pressure to compress the trapped air inside. When a flush is triggered, this compressed air forces the water into the bowl, so instead of the “pulling” or siphon action of an ordinary toilet, the pressure-assist unit “pushes” waste out.

Pressure-assisted systems can reach up to 70-gallon-per-minute peak flow rate. This flushing force can improve drain line carry—the distance a flush propels waste matter through a drainpipe under test conditions. The best gravity toilets meet the American National Standards Institute recommendation of 40 feet, but pressure-assisted toilets deliver up to 60 feet of carry—a 50 percent advantage.

Most residential toilets—and even many commercial toilets—are standard gravity-flow models that can range from old, inefficient toilets that use up to 5 gallons of water per flush to newer toilets that only use about 1.6 gallons per flush (GPF). However, these more efficient gravity-flow toilets can lack the power necessary to fully flush waste, so if you regularly have problems with flushing power, a pressure-assisted toilet may be the best option.

The first pressure-assist toilet was developed in 1984 in response to concerns over water shortages, and they have become progressively more powerful and economical. Other “green” or water-conserving toilet designs, such as dual-flush and composting toilets, are also available to the consumer, although gravity toilets are still favored in most situations.

Comparison between gravity assisted toilets and pressure-assisted toilet

Cheaper More expensive
Easy to repair Higher flushing power
Easy to find parts for Excellent for office or industrial use
Easy to clean Needs to generate pressure to operate
Most popular Loud
Clogs easier More resistant to clogs
May need multiple flushes to dispose of waste Difficult to repair
Excellent for home use Difficult to find parts for

How Pressure-Assisted Toilets Work

pressure assisted toilet

A typical residential toilet will have a large porcelain tank that fills with water and a bowl that acts as both a seat for the user and a water-filled collection point. When the toilet is flushed, a flapper lifts off of the flush valve, allowing gravity to force the water from the tank down into the bowl and push any waste into the drainpipe. A pressure-assisted toilet takes this system a step further by having an airtight plastic tank inside the large porcelain tank in order to improve the flushing power.

The airtight plastic tank fills with water between flushes, but it’s designed to trap air inside the tank, increasing the air pressure as more water fills the tank. When the toilet is ready to flush, it uses the built-up air pressure to explosively force the water from the tank into the bowl at a much higher velocity than a gravity-flow toilet. Despite the increased power, these toilets actually use less water per flush than a gravity-flow toilet and don’t require the trap way to be increased in size because larger waste is broken up by the force and velocity of the water.

Benefits of switching to a pressure-assisted toilet


1. Increase in flushing power and not in water consumption, in fact, pressure-assisted toilets typically save a household about 0.2 to 0.5 gallons per flush, or 4,000 gallons per year, reducing the cost of your water bills and promoting water conservation efforts.

2. The enhanced flushing power reduces the need for second or third flushes to clear waste from the toilet bowl. Instead of relying on gravity and centrifugal force to push waste out of the toilet bowl, the built-up air pressure in the tank blasts water into the toilet bowl, ensuring that waste flushes effectively.

3. The high-velocity flush of a pressure-assisted toilet tends to break up large pieces of waste, preventing clogs in the toilet and further down the drain line.

4. Reduce cleaning frequency and condensation problems, the strong force of the flush removes debris from the inside of the toilet bowl.The water level in the toilet bowl of a pressure-assisted toilet is higher than the water level in a gravity-flow toilet. The increased water level helps to keep the sides of the bowl clean during use. Condensation is less of an issue because the water is stored inside an airtight plastic tank instead of a porcelain tank.

Advantages of using Pressure-Assisted Toilets

hotel pressure assist toilet

1. The toilet is exceptionally stronger than traditional, gravity flow models and flushes more waste using less water.

2. The bulk of water is located in the bowl, thus toilets stay cleaner. Reduce the amount of cleaners and labor to keep the toilet clean. It helps to reduce the amount of chemicals entering the environment.

3. The two-tank system reduces condensation and sweat, it will not contribute to increased humidity in your bathroom.

4. Due to its powerful flushing action, a pressure-assisted toilet will clog less often than gravity flow models. This benefit can be especially helpful in older homes with dilapidated sewage lines that are subjected to frequent clogs, as the extra power of the flushing action can push waste past sticking points within the sewage line.

Dis-advantages of using a Pressure-Assisted Toilet

old fashioned pressure assisted toilet

1. The fact that these toilets are louder and produce more sound when flushed versus traditional, gravity flow toilets.

2. Due to their limited use, parts for this type of toilet are harder to find. Many hardware stores and/or home improvement centers do not stock their parts on the shelf, requiring you to special-order them or visit a plumbing supply house.

3. Pressure-assisted toilets cost significantly more than traditional gravity flow toilets.

While pressure-assisted toilets seem to be more expensive, over time you will end up saving money. Gravity-assisted toilets are the most popular and most economical options as they are cheap and effective. In general, gravity toilets are more than sufficient to meet the needs of most household and commercial settings, but can be less than optimal in terms of sheer volume efficiency than pressure-assisted varieties. For larger scale plumbing needs, pressure-assisted toilets may be optimal.