Sand in pool

[Watermom]

Disappearing from view means that you cannot see the dot at all. It is a tough test to read.

[PoolDoc]

Disappearing from view means that you cannot see the dot at all. It is a tough test to read.

Unfortunately, it's the best available. The very weakest test on test strips is the CYA test. The next step up, from the disappearing dot test, requires an expensive electronic instrument to peer through the cloudy water . . . still not super accurate. And, the step up from that requires a GCMS (gas chromatograph - mass spectrograph) that runs $15,000+.

Personally, I would probably say that it's a bit of a pain to get used to, but that once you are accustomed to the test, it's not really hard at all. And fortunately, it is accurate enough to get the job done, and cheap enough to be practical.

[nefretrameses]

Update:

The pool consistently looks great. I have been maintaining appropriate balance and have raised CH to 250. The amount of "sand" has steadily decreased. Many days none is visible, although y o u can feel it on the bottom of the pool in spots. The sides feel smoother and very little material comes loose when I rub my hand on it. I'm concluding that a combination of low CH and low PH over an extended period of time softened the finish and caused it to come off. I'm considering taking my CH higher, maybe 300 or 350. I am using cal-hypo but will switch to bleach when I hit my CH target. Any opinions?

FC=7.2
TC=7.2
PH=7.6
TA=80
CH=250
CYA=80

[PoolDoc]

Might want to raise your TA a bit, instead. It's easier to adjust, than calcium.

[nefretrameses]

But isn't CH more related to possible surface damage that TA?

[PoolDoc]

Actually, by far the most important factor is pH, or rather, pH + temperature. After that, it's alkalinity, and then calcium. There is a sort of exception: because of the way the process of dissolution or precipitation works, if either alkalinity or calcium are near zero, or even less than 60 ppm, THEN their significance goes way up.

Water, in the presence of calcium materials, will NOT stay near zero in calcium long!

[nefretrameses]

Thanks Doc. It's interesting though. It's been about 6 weeks since I got my Taylor test kit and was able to get my water balance in some kind of control. I also assumed PH was an important factor, and based on the advice I got here, I immediately raised it, and have maintained it, in the appropriate range since I got my test kit. But I still had "sand" in similar amounts compared to before I sought your advice. I finally found a source for CaCl, since it's pretty rare in Florida, (Fastenal) only two weeks ago. Once I had it, I raised CH from 180 to 250 over a three day period. Since then, it seems that the amount of "sand" has lessened. Of course this is a perception, since I have not measured the amount in any way. The smoothness of the sides also improved since raising CH (again a perception). Maybe this is just the result of having the PH in the proper range for that 6 weeks rather than the result of having the CH raised for 2 weeks. Or maybe a combination of both?

I don't think either CH or TA ever got anywhere near zero, or even less than 80 at any time. My fill water has a TA of 180 and CH of 110.