Posted on Leave a comment

What Exactly Is a Washdown Toilet Pan?

Washdown Toilet Pans

The washdown toilet pan is the base of the toilet that connects to the drainage system. A washdown toilet uses the gravity of water to push waste from the water bowl to the drainage system. In a washdown toilet, the water pours from the tank in the bowl pushing away the waste. This type of toilet uses a washdown flush system.

It only “pushes” and does not evacuate the bowl. These toilets have small water surface areas in the bowls that are deep down in the bowl.

What is a Siphonic Toilet?

Siphonic toilet have a long and narrow ‘P’ or ‘S’ shaped trap way. Which ends in the inlet of the bowl, and the other connects to the drainpipe. This trap-way design creates a siphon. They use a gravity flush system. Pulling the lever opens and lets the tank water flow into the bowl. The water quickly rises and sinks in the toilet bowl. The Water flows faster from the tank and exits the bowl immediately. It occurs due to the larger flush valve diameter than the drainage pipe.

When water exits through the drain pipe, displacing the air inside the trap way or drain pipe creates a vacuum. When it flows in a trap way, the siphon begins to work. It is also indicated by decreased water in the toilet bowl. Some siphonic toilet create a swirl, but the working principle is the same. 

This swirl is because of the toilet bowl siphon in the Siphonic toilet. It’s like a gentle push that uses the minimum energy of water. It maintains the water level and cleans the toilet bowl thoroughly.

The siphon is strong enough to suck the heavy solid waste with the water. A babbling sound is heard at the end of a flush. This is produced when the vacuum is broken, and the siphon is stopped. The bowl then gets filled with leftover water and the tank starts to refill for the next flush. The above information is the answer to what is a siphonic toilet.

Who Invented the Flush Toilet?

Who invented the flush toilet? Well, nobody thinks about it. This is why the flushing toilets of the 21st century haven’t changed much since it was first patented in 1775 by Alexander Cumming, a Scottish watchmaker. Cumming’s toilet was a slightly altered “water closet” designed for Queen Elizabeth I by her godson Sir John Harrington in 1592 — Cumming’s has an S-shaped pipe to trap bad odors while Harrington’s design had nothing to cover the bad odor. Of course, self-flushing toilets, heated seats and vacuum potties, and tour buses were invented later. 

Washdown toilet vs Siphonic toilet

This is a big debate in countries like Germany, Russia, and Colombia. This is because the toilets are well preferred in both countries. As discussed above they both use different types of toilet flush systems. These toilet flush systems are namely Washdown toilet flush system and Siphonic toilet flush system or a pressure-assisted flush system.

These toilets differ in many factors such as bowl size, Water usage, trapway, spare parts, maintenance, cleaning, odor control, whole toilet size, and comfortability. These qualities run neck and neck in both types of toilet systems and hence the decision of washdown toilet vs siphonic toilet is difficult to conclude. However, we will see all the above qualities for both of the toilet systems.

Bowl size

The bowl sizes of washdown toilet seats and siphonic toilet bowls are different. These sizes are according to the water action inside these bowls. Typically, the washdown toilet bowl size is 4”x 5”, where 4” is the diameter. The size of a siphonic toilet bowl is 7.5″ to 10.5″. The size of the siphonic bowl size is bigger than the size of the washdown toilet bowl. The washdown toilet have a smaller space because the working of washdown toilet specifically uses the gravity of water to push the hard waste into the trapway. Whereas the siphonic toilet bowl uses a vacuum and creates a siphon to pull the waste into the trapway. 

Water usage

The water usage in a washdown toilet is much less than in a siphonic toilet. Since the washdown toilet just uses water to push the waste in the trapway. The siphonic toilet uses water to create a vacuum and move the waste inside the trapway. A dual flush is fitted in a washdown toilet where the use of water is 3 or 6 gallons per flush and the siphonic flush requires 6 gallons of water per flush. Dual flushing is not for siphonic toilets. 


Trapway is different in both washdown and siphonic toilets. It is because of the flush water actions difference. The trapway of the Siphonic toilet is “S” or “P” shaped to create a good siphon. The trapway of a washdown toilet is shorter and wider. However, the trapway in a siphonic toilet is narrower and has more chances of clogging. The surface area of a washdown toilet trapway is larger than the surface area of a siphonic toilet trapway.

Odor control

The Odor of waste remains controlled in a siphonic toilet system. Washdown toilets are less preferred in countries like Germany, Russia, and Colombia. Because of their lack of odor control. As we know the siphonic toilet creates a vacuum hence getting rid of the odor. This characteristic depends on the types of toilet flush systems used in different toilets.

Whole toilet size, Maintenance, and Cleaning

The size of a washdown toilet is more compact than a siphonic toilet. Due to the “S” shaped trapway of siphonic toilet the size of the whole set becomes bigger. The maintenance of both systems is somewhat similar. The washers of both systems need replacements. The float valve and flush valve rarely need to be replaced. However, the flush buttons’ and levers depend on their quality. The cleaning of these toilets depends on the number of holes from where the water comes down. This is mainly because these holes leave watermarks in the bowl. People from countries like Germany, Russia, and Colombia use toilet brushes as an accessory for cleaning along with the plunger for clogging. 

Advantages of Washdown Toilets

Washdown toilet have many advantages as well as disadvantages. These toilets are popular in countries like Germany, Russia, and Colombia because of efficient flushing, less water usage, easy cleaning, simpler mechanisms, less clogging, and compact design.

Best Washdown toilet have a powerful flushing mechanism, which flushes waste effectively in a single flush. This in turn reduces clogging and water usage, making them an environmentally friendly option.

Best Washdown toilet have a direct water flow in toilet bowls. This maintains a clean and hygienic bathroom. Washdown toilet have a simpler design than Siphonic toilet. This makes washdown toilet low maintenance and reliable. Washdown toilet are more compact making them a suitable choice for smaller bathrooms. The washdown toilet flush parts have a simpler mechanism.

Disadvantages of Washdown Toilets

Despite many advantages, washdown toilet also have some drawbacks like Noise Level, Splashing, toilet flush problems, and Higher Costs. 

Washdown toilet are noisier than Siphonic toilets because they have a direct and forceful water jet during flushing. The odor issue is one of the biggest toilet flush problems. The powerful flushing of washdown toilet results in splashing of water, which is unpleasant for some users. While the initial cost of a Washdown toilet is lesser than that of a Siphonic toilet. But the value of maintenance makes the overall value similar to Siphonic toilets.

Advantages of Siphonic Toilets:

Siphonic toilet, also known as siphon jet toilet, has a powerful flushing performance with their toilet bowl siphon, odorless environment, and water-efficient design. Siphonic toilets have a unique trapway design and pressure-assisted flush system to create a powerful suction effect. This powerful flush action reduces the clogs and creates a clean and hygienic toilet experience. Hence, a siphonic toilet is also called a siphonic jet toilet.

Siphonic toilets are known for their water efficiency. By utilizing the siphon jet mechanism have a complete flush with as little as 1.28 gallons per flush (GPF) in comparison to 3.2 GPF of washdown toilet. This reduces water bills and helps the environment. The siphon jet action creates a smooth flush and minimizes noise. Siphonic toilets are generally quieter making them suitable for bathrooms in bedrooms, apartments, or households with noise sensitivity.

Siphonic toilets often have a compact and space-efficient design, making them a good choice for smaller bathrooms. The trapway in siphonic toilets is located at the back of the bowl, allowing for a more streamlined and compact shape compared to washdown toilet. Siphonic toilets come in a variety of styles and designs, allowing homeowners to choose one that complements their bathroom décor. They are often available in modern and contemporary styles, with sleek lines and hidden trap ways, enhancing the overall aesthetics of the bathroom.

Disadvantages of Siphonic Toilets:

Siphonic toilets typically have a high initial cost compared to washdown toilet. This is reasoned by their complex design and manufacturing process. Siphonic toilets require more maintenance than washdown toilet. The siphon jet mechanism and trapway require cleaning for proper operation and clogging prevention.

Siphonic toilets are not compatible with the older plumbing configuration. The siphon jet mechanism requires a specific type of drainpipe and venting system to function properly. The washdown toilet flush parts have a complex mechanism.


The advantages and disadvantages of both Siphonic and washdown toilets are listed above. The above article explores two of the most liked toilet systems in many countries like Germany, Russia, and Colombia. 

Must Read:

Must Read: