filling up pool

Oct 20, 2007
Hello everyone, I have a question regarding water evaporation. When filling my pool with municipal water, say about 4'' I guess about 300 or so gallons, do I need to adjust my chlorine, ph and ta? Does adding that much water affect the chemistry of the pool? Should I add chlorine, say 2 cups, while I'm filling the pool? Thank you for your responses.


TFP Expert
Platinum Supporter
LifeTime Supporter
May 7, 2007
Silver Spring, MD
Yes and no. Any addition of water will affect the chemistry, but adding a small amount of water probably won't affect the chemistry enough to need to worry about it. Unless your fill water is fairly extreme in some way you can ignore it and simply test the water on your regular schedule.


LifeTime Supporter
May 4, 2007
Need to know the dimensions of your pool and depth. If your pool averages 4 feet deep and you are adding 4" of water that is roughly 1/12 of your volume so it is about 8%. I live in Miami and our Municipal water has 2ppm CL, TA 60, CH 100 so I guess yours might be the same so it does not make a huge impact right away. I would test the next day and make adjustments as neccessary.

I also tested the PH of our rain water and it was 7.6 so it was not acidic as I thought. I have only tested it once and don't if rain PH varies from one day or season to another.