Please help with FC/CC test and my pool

[Yunfeng]

So, I am new to an old pool and to TFP as well. This is my first time to use Taylor 2006C to quantify FC/CC. First two steps are simple and I waited for the power dissolved, then added the brown bottle solution drop by drop until it turned whole thing colorless. However, after about 1 minute, the colorless started to turn into light pink, so I added another drop from brown bottle. After swirled the tube, the water sample became colorless again until one minute later it showed light pink. The cycle just went on and on for about 7-8 times before I finally determined to stop the testing. Is this normal for the kit or did I do anything wrong?

I might be the third owner of my current pool and there is no any document I could find after I moved in. It is an irregular shape pool with both shallow end and deep end. So, I have tried to estimate the size by the corresponding change of TA, muriatic acid added, and the volume of water. For example, about 30 ppm of TA was brought down when I added 1 gallon muriatic acid to my pool. According to some table online, I estimated that my pool is about 17500 gallon. Dose my estimation make sense?

Thanks a lot for your help.

 

[GOONiE]

first time it goes colorless is the correct reading.

 

[ajw22]

Muriatic acid prinaily lowers PH. Lowering TA is a byproduct of lowering PH then having it rise.

What was your PH before you added the MA and what was the PH 2 hours after adding the MA? Assuming your pump was running during that time.

 

[JamesW]

1 gallon of 31.45% acid will lower the TA about 30 ppm in a 16,500 gallon pool.

If you could measure TA exactly, that would be reasonably accurate.

However, the TA test is accurate to about 10 ppm. So, you're not going to get a reliable estimate of pool volume.

If you do the test multiple times and average the results, then you're going to get a closer approximation for pool volume.

Do the estimate for every chemical you add and keep a running average of the estimated pool volume.