Hello, not sure if my CH is really this high or if my testing is not accurate....
Our tap/fill water is normally quite hard (tap can often be 300-350 ppm or more). For the last couple of years, anytime I've measured the CH of my pool it's been in the 350-375 ppm range. Because it's been very consistent, I hadn't checked it for several months. Today I checked it and measured around 850 ppm! I repeated the test and got the exact same result. Just to see whether or not I would get an unexpectly high number for our tap water, I tested it and measured 200-225 ppm. This is actually a little bit lower than I expected for our tap water, but it still seems reasonable, knowing that our water hardness does fluctuate throughout the year. So....
1)Could the 850ppm really be correct for my pool? I basically just use liquid chlorine to sanitize (no cal hypo ever). What factors would make it rise to this level? BTW, pH is currently 7.4 (just lowered it a bit yesterday - it likes to rise if I don't stay on top of it with acid), and my TA is at 80 ppm (it's been 70-90 ppm pretty consistently for the last couple of years).
2)Is there an issue with my test? I'm using the Taylor reagents and a magnetic stirrer. I did get what I initially thought was a fading purple endpoint, because at one point the sample stayed the same purple shade for several drops. But eventually it did change to the pure blue color that I expected, and stayed the same blue shade after a couple more drops. (I did not get any 'hanging purple' when doing the tap water test, but the CH level was a lot lower in that case.)
Regarding the purple, I know that once the color changes and remains the same, the test should be considered over. But then again, after more drops I did get to the blue color. And if my CH was really 850 I can see that it might be reasonable for the sample to be red/pink for quite a while (and it was), purple for a while, then finally the expected blue color.
Thoughts or help? The CH test did eventaully reach the normal blue color that I expected, so it seems like it worked OK, but the CH result I got for my pool sure seems unreasonably high.