Why Does the Shower Steam Up when the Water Isn’t at Boiling Point?

This question doesn’t really relate to drain cleaning, but it’s still an interesting one. Whilst we were out clearing a blocked drain last week a customer of ours asked us, and we thought you might like to know too. While it’s a simple answer it can be a little tricky to explain and understand the technicals of it, so we asked our local hot water installer to give us a full rundown. Here is what they told us.

In many instances when people are showering, there is steam in the bathroom. Normally, steam comes as a result of evaporation where water, which is a liquid, is subjected to heat. When the heat to which water is subjected reaches a certain point, the water changes state from liquid to gas. It is this gas that is known as steam and the process of change from liquid to gaseous state is known as evaporation. Usually, this process is accompanied by boiling. Boiling takes place when air leaves the water due to heat.

Evaporation

Boiling water would be too hot for anyone to shower under. It is therefore obvious that even if the water is hot, it certainly cannot be boiling, yet there is usually a lot steam in the bathroom. The first reason for this is that water does not need to boil to evaporate. Evaporation takes place as long as water is heated regardless of whether it has reached boiling point. The two are different processes. Evaporation is a process that takes place on the surface. It involves a change of the state of water from liquid to gaseous state.

When the heat is not enough to cause complete evaporation, some of the molecules in the water molecules attain enough energy to leave the rest of the water and appear as vapor. In some instances, this is what happens with the water in the shower. If the water in the bathroom is warm, then steam can be expected. This phenomenon is at times the same as when steam can be seen coming from the ground after a light rain shower. 

Condensation

The determinant for this process includes the temperature of water coming from the shower, the temperature of air in the bathroom and the level of humidity in the air in the bathroom. The surface area of the exposed area is also an important factor in this process. When steam appears in the bathroom, it originates from the showerhead. This is because when the water that comes from the showerhead is warmer than the air in the room. 

Even if the difference in the temperature of the water from the shower and the air in the bathroom was only marginal, it would still have the same steaming effect. The air in the room is usually very humid, owing to the fact that there is water spilling to the floor it is this water that condenses into water vapor that can be seen in the bathroom. If the temperature in the room was the same as the temperature of the water, then there would be no visible steam. 

While there are instances where evaporation causes steam in the bathroom, steam in the bathroom is usually as a result of condensation. The inability of the air that is moving around the room to hold as much water as the water near the showerhead is caused by the fact that the air gets colder as it moves around the room. It is in this state that the humidity in the air turns into vapor.