- Oktober 12, 2023
- Veröffentlicht durch: Ivica J
- Kategorie: Blog
How Does a Toilet Siphon Work?
A toilet’s u-shaped portion is the driving force behind its flush. As water from the tank enters the u-shaped portion, it is aided by gravity to create an upward and downward toilet siphon that transports bowl contents through the power of gravity.
When flushing, 2 gallons of water rush in rapidly before pressure shifts and air enters to interrupt the siphon and create the distinctive “gurgling sound.”
The Siphon Tube
A toilet’s siphon tube is an inverted “U”-shaped pipe connecting the bowl (the higher reservoir) to the sewer/cespool (the lower reservoir). When flushed, water within the tank rushes over this U-shaped trapway into a descending exit tube where gravity and vapor pressure from two gallons of liquid force it downward, siphoning wastes down towards the drain.
Scientists have long debated how siphons work, with most agreeing on atmospheric pressure and liquid cohesive bonds being key factors. When fluid starts flowing down from a long arm and creates a partial vacuum behind it, it pushes it upward through one of three channels until either: (1) either it empties out of its container; (2) water levels balance out or air enters one or both short legs; or (3) gravity takes over to draw it all back down until reaching its outlet point.
The Siphon Jets
When you flush a toilet, water enters quickly enough to overcome a partial vacuum that forms within a tube leading down to the drain. This tube, called the siphon jet or rim jet, directs some of this water through small openings in its rim of the bowl rim. As more and more water enters quickly enough, its rapid influx raises the water level in the trap and forces waste and other materials up the pipe and down into the drain.
Experimenting with these jets is easy by pouring a cup of water into your toilet bowl and watching as its level rises slightly, yet still falls short of filling the siphon tube completely.
Pouring a mixture of vinegar and baking soda into the toilet tank and brushing all jets with a brush will help clear mineral deposits over time. While there may be other effective cleaning solutions out there, this one is both safe and relatively cost-effective.
The S-Shaped Trapway
The S-bend of the toilet trap creates a pool of water which acts as a seal against germs and unpleasant odors from infiltrating into your bathroom, while also protecting against trapped sewer gasses from entering into your house. This little pool also helps prevents any sewage gasses from becoming trapped inside your house.
As tank water rushes down the drain, it fills a S-shaped siphon tube mounted at the rear of your toilet and fills its S-siphon action quickly pulls nearly all bowl and tank water down within 4-7 seconds–it flushes!
Rushing tank water then breaks the continuous column of water in an S-shaped trapway, allowing air to enter and stopping its siphoning action. While an S trap may dry out at times, allowing sewer gases back up into your home, P traps have an air admittance valve (AAV) installed into their vent pipe to keep airflow open while also preventing siphoning. To maintain proper functioning of both types of traps in your toilet system, installing AAVs could prevent siphoning.
The Exit Tube
If you were to pour two gallons of water into the toilet bowl, gravity would work its magic and flush it away quickly and efficiently. This is due to the u-shaped trapway section connecting to the bowl (and going below floor level) being higher than the drain itself.
Standing water in the U-shaped portion of the trapway helps form a seal to block sewer gases from seeping into your home, making standing water an essential component in bathroom design.
Flushing involves approximately 2 gallons of water rushing quickly up the U-shaped portion of the trapway to fill a siphon tube. Once full, air enters and interrupts its flow causing that distinctive gurgling sound which indicates you’ve just flushed your toilet. Once full again, tank water refills both bowl and cistern until its float rises above an acceptable threshold, stopping its fill valve.