What Does the Siphon Jet in a Toilet Do?

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Toilets have come a long way since the lowly outhouse. A variety of flush-improving toilet technologies have been developed to ensure the average user gets the most out of an ever-decreasing flush size. The siphon jet is another technological leap in toilet plumbing, helping to increase the power of a flush without increasing its water volume.


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The siphon jet is a feature on some toilets to help with the flush. Extra water sits in a molded pocket and adds water pressure when you flush the toilet.

The Basic Gravity Flush

A toilet bowl is designed with an air pocket in the bend that enables the formation of a vacuum. When you push the handle on the toilet tank, a valve releases the water held in the tank into the bowl. This action overcomes gravity and the toilet's nature to hold water in the bowl by creating a vacuum that sucks the contents of the bowl down into the drain.


This type of toilet is the most common, and it's inexpensive. However, the flush can sometimes be weak and doesn't always push everything down the drain easily. This often results in toilet clogs or the need to repeat the flush to get everything down.

Problems With the Tiny Flush

Old-fashioned water-wasting toilets have a 5-gallon flush. The sheer volume of water rushing into the bowl forces anything and everything down the drain. Since water conservation efforts began in the 1980s, the standard flush has dropped considerably. The early 1.6 gallon-flush models were often inefficient at removing solid waste and toilet paper, prompting the improvement of the flush.


Enter the Siphon Jet

The siphon jet is a molded pocket in the front of the toilet that holds extra water until a flush is initiated. It points directly into the trapway. When the toilet flushes, the vacuum action pulls the stored water out of this pocket, increasing the pressure of the flush. It is a feature found on many, but not all toilets, so check the features if you're buying a new toilet for your bathroom.


Siphon Jets Tested

The University of Washington tested a variety of siphon jet toilets before replacing 2,000 of their older style toilets with more efficient toilets. Among the tests was an examination of the amount of toilet paper each toilet could flush at one time. In this test at 25 psi, the Toto toilet outperformed all the others, flushing an impressive 40 feet of paper. The runners-up were toilets by Kohler and Crane. Overall, however, Crane led the pack on other study tests, followed closely by Toto and then Kohler.


Pressure-Assisted Toilet Option

If you want even more power for each flush, you can get pressure-assisted toilets for your home. A pressure-assisted toilet features an air bladder inside the toilet tank to improve the flush. It uses air pressure to improve the flush, decreasing the chances of a clog without using extra water. On the outside, these pressure-assisted look the same as any other toilet, so they'll fit into your bathroom like any other toilet.



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