The exhaust system of your car represents the last leg of the combustion process. When most people think of tail pipe emissions, they imagine carbon monoxide and the other negative byproducts associated with vehicles.
Often times, however, drivers are surprised to learn that one common byproduct of combustion is also one of the most familiar compounds on Earth – water. As a result, it’s common and completely normal to see water dripping or “leaking” out of the end of your car’s exhaust system.
In order to understand how water ends up in your tailpipe, you must first review some high school chemistry. Both gasoline and diesel fuel are formed from thousands of hydrocarbons, compounds that contain hydrogen and carbon. An engine creates the energy needed to power a vehicle by igniting these hydrocarbons in the presence of oxygen. When hydrogen (H) and carbon (C) combine with oxygen (O) in the combustion chamber, they create water (H2O), carbon dioxide (CO2), a fairly small amount of carbon monoxide (CO), and then small amounts of other miscellaneous compounds. There’s also some unburned fuel in the exhaust too, but that’s burned in your car’s catalytic converter…and that’s another topic.
Now that you know how water is created, how does it make its way out of the tailpipe? Initially, the water is in gaseous form much like the vapor you see when boiling water on a stove. As the water vapor moves toward the tailpipe, it will cool. If it cools off enough, it can start to condense on the inside of your exhaust pipe and then drip it’s way out of the exhaust. As you may know from experience, it’s extremely common to see exhaust pipes dripping in the winter. This is because the cold outside temperatures cool the exhaust gases before they can make it all the way out of the tailpipe.
Although the presence of water in the exhaust system is normal, it can cause problems over time. Making short trips can trap water in the exhaust system because the system never gets hot enough to turn the water into steam and push it out of the tailpipe. Stagnant water inside your exhaust system – and in particular your muffler – will lead to rust at some point, which will impact your gas mileage and the way your exhaust system sounds. The solution? Avoid making short trips in your car. If your exhaust system can reach full operating temperature (which usually takes 15-20 minutes), there’s little risk of water collecting inside.
So, there you have it: water drips out of your car’s tailpipe because water is a natural byproduct of combustion. Isn’t science grand?
About the Author: Jason Lancaster is the editor of ExhaustVideos.com, a website that helps vehicle owners find the best sounding exhaust systems.
Credits: Photo courtesy of Arthur Caranta.