How to know exactly how many gallons my pool has

phillipjko

Active member
Apr 13, 2015
41
Nashville
#1
I have a 18 x 32 pool.. shallow part (nearly 1/ of the pool) slopes from 3ft to 6 ft and then drops to 8 - 8.5 ft. Rectangular pool. With pool calculator it shows as 30,000+ gallons but I think it is not that much. As I need to buy 40lbs bags of salt. How many bags of salt do I need or exactly how many gallons do I have?
 

kimkats

Mod Squad
LifeTime Supporter
Jul 10, 2012
36,013
Tallahassee, FL
#2
Play with your PH levels. If you PH is at 7.5 right now go to pool math and see how much muratic acid you would need to add to push the PH down to 7.3. Add it, let the pump run for about 30 mins. then retest. If it went lower than the target add 500 gallons to your pool size. If it did not got as low as the target then take away 500 gals. Play with it this way over a couple of days and you can dial in the gallons within about 500 gals.

Kim:kim:
 

JVTrain

TFP Expert
Feb 3, 2014
5,080
Central Minnesota
#3
pH can be a little tricky for calculating volume, as it's influenced by TA and less stable over several days, but doable. You could use your first salt additions to measure your pool volume. You'd have to have a salt test; ideally a drop based for a bit better accuracy. Measure your initial salt level. Figure out the ratio of your expected concentration versus your actual measured after adding and that gives you your actual volume. Calcium hardness and CYA are other good levels to use as well.
 

pabeader

LifeTime Supporter
TFP Guide
May 14, 2015
4,349
Cartersville Ga
#4
I have a 18 x 32 pool.. shallow part (nearly 1/ of the pool) slopes from 3ft to 6 ft and then drops to 8 - 8.5 ft. Rectangular pool. With pool calculator it shows as 30,000+ gallons but I think it is not that much. As I need to buy 40lbs bags of salt. How many bags of salt do I need or exactly how many gallons do I have?
When I do the calc I get around 24800. So I think the size you have listed in your sig is pretty close.