Using change in FC level to measure pool size

[kichi]

I am helping a friend set himself up for self pool maintenance. Ran the tests on his pool last night.

FC 3.5
CC 0.5
CYA 90

He has an odd sized pool. Our initial estimate of pool size was 15K gallons, and we added in 3 gallons of Chlorox. FC was 21.5 after 2 hours indicating we overestimated the pool size.

Can I use the change in FC levels to estimate his pool size (should be ~10K gallons based on the change in FC assuming no algae given low CC levels)?

The test was done in the evening so little Chlorine should be lost to the sun. The only piece I am not sure how to incorporate is the high CYA.

Thoughts?

 

[tim5055]

Yes. While it may take multiple applications of different chemicals to get a more percise volume that way it can be a good way to verify the size.

I also have an odd shaped pool and narrowed my size down as best as possible that way watching what specific additions of chlorine and muratic acid did to my FC and pH.

 

[prs]

I found PoolMath generated additions of mutriatic acid to be very accurate for my pool size before I added borates. Not quite so accurate after I added 50 ppm borates.

 

[chiefwej]

Use PoolMath. Put in whatever you think for capacity. As you add chemicals and see if it reacts as predicted, by trial and error, you can dial in the exact size.

 

[jblizzle]

As others have said, you can get an idea of the pool size based on chemical additions. BUT, not just this single data point. For adding chlorine you have 2 independent variables: 1. pool volume and 2. bleach strength. Both would affect the FC ppm rise.

In reality, there is no need to be exact on the pool volume.

 

[kichi]

Great. Thanks everyone for the quick response.