Alkalinity Zero

[kelemvor]

When you test your alk, use the 10ml sample size instead of 25ml. The loss in precision will have no bearing on how you dose your pool. Also, using the smaller sample size means you save reagents and time by using less drops to achieve the color change.

[chem geek]

Testing for chlorine in a FAS-DPD test with a 10 ml sample size makes sense since 0.5 ppm resolution is usually sufficient compared to 0.2 ppm with a 25 ml sample size. Calcium Hardness (CH) is another test where one could use a 10 ml sample size for a 25 ppm resolution. However, for Total Alkalinity (TA), the resolution of 10 ppm with a 25 ml sample size is usually needed. For initial TA adjustments the smaller sample size may be OK, but when making final adjustments the 10 ppm resolution is preferable.