Indoor Pool almost complete, could use some advice

[aylad]

Hi,

Unfortunately the traffic on this forum is very, very slow this time of year since most of our folks have closed their pools for the winter. Some of the regulars still check back in, but not as frequently, so don't give up if it takes several days or even a few weeks to get some responses to this thread--please keep checking back on it!

I can't answer your questions, but I just wanted to make sure you knew that your post is NOT being ignored, it's just a slow time of year around here....

Welcome to the forum!

[chem geek]

It is absolutely positively not true that if the air is warmer than the water that evaporation will not occur. Why do you think that? Unless the temperature difference is large, it's only if the humidity in the air is close to 100% where evaporation will not occur because the air is already saturated with water vapor which is another way of saying that it is in equilibrium with the water. Technically, if the air is warmer than the water, then evaporation will stop below 100% relative humidity because warmer air holds more water vapor (so a smaller relative humidity has the same water concentration as air saturated with water vapor at a lower temperature), BUT it won't stop at lower humidity levels. If there is no wind or pool activity, then if the air temperature is 100ºF and the water temperature 70ºF then evaporation stops when the relative humidity gets up to 38%. However, if the air temperature is 82ºF and the pool water temperature is 80ºF, then evaporation would only stop when the relative humidity got to 94%. At 50% relative humidity, there would be 0.15" per day evaporation. At 0% relative humidity, it would be 0.32" per day.

It should be obvious that warm dry air does not prevent evaporation because desert areas such as Arizona have very high evaporation rates even when the water is cooler than the air. The water temperature for larger bodies of water including pools tends towards the average of day/night temperatures, but during the day the air temperature is warmer than this average yet evaporation still occurs.