Our pool is irregularly shaped with a sunshelf and several swim-outs which makes accurately calculating the total pool volume difficult. I am gearing up to try the chemical method outlined at http://www.troublefreepool.com/threads/64047 that requires measuring TA to within 1-2 ppm.
The standard approach to increasing test accuracy is to increase the amount of pool water being tested. This results in each drop of R-0009 corresponding to 1 ppm instead of 10 ppm. Given that the volume calculation method requires testing TA twice, I was thinking of a way to avoid using that much R-0009 (~150 drops).
What if I used the standard volume of pool water but instead diluted the R-0009 prior to dropping it into the tube? In other words:
- start with 25 ml of pool water (per the standard instructions)
- add the standard 2 drops of R-0007 and 5 drops of R-0008
- dilute R-0009 1:10 by adding 10 drops (0.5 ml) into 4.5 ml of water (mix well)
- add the diluted R-0009 until the color change with each drop corresponding to 1 ppm
This could be made even faster by adding undiluted R-0009 until you are within 10 ppm of the result (i.e. if you know the TA is between 60-70, you could add 6 undiluted drops then switch to the diluted drops).
I can think of a few issues and would love to hear feedback from the experts here:
- What to dilute the R-0009 in? I imagine that tap water would be fine since you are adding <5 ml of tap water into 25 ml of pool water. The alternative would be something like double-distilled water (ddH2O). Or is there a known diluant to use to further dilute R-0009?
- What to use to drop the distilled reagent into the tube? Would a standard dropper work?
- Is there too much error introduced by diluting R-0009 1:10? If so, the method could be modified with a less aggressive dilution.
Looking forward to hearing your thoughts.