CYA testing

[chem geek]

Your "glassware" only tests cya up to 30? That doesn't make much sense to me since 30 is at the low range of normal. Or even too low.

Most test kits that test for CYA have a measurement tube that starts at 100 at the bottom (i.e. adding a small amount of rather cloudy liquid will obscure the black dot) and often ends near the top of the tube at 30 (i.e. it takes a lot of liquid to obscure the black dot).

KirstenHW found that it took even more water than filling the tube to the 30 level line and that continuing to fill the entire tube beyond this last calibration mark had the black dot go away. In my Taylor K-2005 kit, the 30 line is close to the top of the tube and much closer to this tube top than it is to the 40 line below it. Since the scale is logarithmic, filling to the very top of the tube is probably a CYA of around 27-28 ppm.

A CYA of 30 is not necessarily too low. It's partly a matter of taste and how much chlorine reserve you need due to the amount of regular chlorine loss you have. I run my pool at around 15-20 ppm CYA with lower corresponding 2-4 ppm FC levels, but I only lose 0.5 ppm FC or less per day since the pool is covered most of the time (it's an electric opaque pool cover).

Richard

[hulla]

Most test kits that test for CYA have a measurement tube that starts at 100 at the bottom (i.e. adding a small amount of rather cloudy liquid will obscure the black dot) and often ends near the top of the tube at 30 (i.e. it takes a lot of liquid to obscure the black dot).

Oh yeah, thanks for clearing that up.