Sand in pool

[BigDave]

We'll need a CYA level to know how high FC is. But, high FC usually makes pH read high. I would raise the pH with Borax straight away because <7.0 could be much lower.

[nefretrameses]

Retest on 6/20 (am) after adding 1 box borax the previous evening:
FC: 13.0 ppm
CC: 0 ppm
ph: 7.9
TA: 80 During this test the sample turned green and then to yellow vs. red
CH: 200 The sample was "pink" rather than red
CYA: 80 I'm a little confised about what "disappears from view means. I assume that if I can see the dot at all it has not "disappeared from view".

Today the pool has never looked better.

Still trying to determine if the sand (which I'm sure is coming from the pool finish) is the result of low ph etching the surface or if the pool just needs to be re-finished. (not sure when the current finish was applied - at least 5 years)

I am brushing a couple of times a day so hopefully the accumulation of sand will stop with the right ph.

[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?