Automobile Exhaust

The water is a byproduct of combustion. Normally the pipes get hot enough to evaporate the water, but on short trips the water stays liquid. This is why it's recommended that you take your car out on the highway once a week if you normally only do short trips - to keep your exhaust system from rusting.

"...water is a byproduct of combustion..." More particularly, is it gaseous water that condenses in the tail pipe, the coolest part of the exhaust system. As stated above, it's from the engine (or aft CAT (or muffler)).

.....everytime you burn Hydrogen in Oxygen, you form H2O = Water. Its that simple.

Hydrocarbon fuels - gas, petrol, diesel all form water vapour when burnt. I believe that the water volume produced is slightly more than the amount of the fuel burnt. (I have not checked that out recently, but believe it to be true)

On days when the temperature is well below 0°C, you can see the steam coming out of the exhaust pipe....

There are other chemicals in there too and the water vapour is quite dirty because of that, don`t distill it and try drinking it!!

Unless you have fitted your commercial vehicle's diesel engine with a CRT(TM) (Continuously Regenerating Trap), in which case the nasties are removed. There is a film of the MD of the company who manufactures and sells these in Europe drinking the condensate from the tailpipe of a bus so equiped.

Motorbike exhausts often have a drain hole at their lowest point, to help reduce rusting potential (by allowing the water to escape).

All the auto exhaust replies are right about where the water out the exhuast comes from. There is also these conditions causing such a problem.

1- If any number of conditions exist, causing fuel to burn rich or lean, water will blow out the exhuast pipe as you describe. On the lean side: A lean burn can exceed 2000 degrees temperatures. A few rpms of this and the spark tip will become red hot and miss-fire a few cycles. When enought wet fuel collects and soaks the combustion area, it cools down the area and spark will again resume. The catalytic converter will convert the now rich mixture (caused by a lean burn condition) into water and other gases. Those amounts of H20, coating everything from the above conditions condenses when the motor is shut down for the night. You see this water force out. This rich, lean condition is ongoing and rises to the level you describe over time. A good tech and specialize additives can correct those problems caused by gum, varnish, friction. Fix any cause of a vacuum leak and any mal-functioning tune- up associated parts to end the problem.

2- If coolants turned acidic, they eat gaskets. If into the oil or intake area, moisture from this source will cause your problem. R U loseing coolant mysteriously? A tech familiar with both areas may detective the problem in either area.

as guru said it is due to the hydrogen &oxygen combination vapor form & due to pressure change at muffler vapor condensate nothing more