Different target levels

[stabguy]

New member here. I've been maintaining my pool for several months with the help of this site. It's about a 12,500 gallon gunite pool with a salt water generator and bubble cover in sunny Honolulu, Hawaii:



The local pool professional I trust most recommended these levels:

FC 3.0
pH 7.4
TA 120
CH 150-200
Salt 3400

I've been shooting for these levels even though they differ somewhat from the TFP advice. My pH shoots up to 8.0 in a few days. I add about a gallon of muriatic acid per week. TA tends to fall to 90 if I don't add baking soda regularly. FC swings up and down, mostly depending on whether the cover is on or off (sunlight kills chlorine). I sometimes adjust the output of the SWG between 20% and 40%.

Lately there have been white flakes in the end nearest the pump, paper thin, crumbly and not slimy. I suspect they are calcium scale from the SWG as described here. A test revealed that my CH has crept up to 350, so I have the triple-whammy: high pH, high TA, and high CH.

Three questions:
Is there a good explanation why the target levels would be different in Hawaii or for this specific pool?
Should I be concerned about the rising pH and adding so much muriatic acid?
Which reading(s) should I focus on lowering in order to prevent calcium scale?

 

[pooldv]

Man! You Hawaiian pool people have some amazing pools and views!!!

Welcome to TFP. Smart people will be along soon to help with how to stabilize your ph. I'm not there yet either.

 

[jblizzle]

1. No. The local "professional's" recommendations are dangerous in that there is no mention of CYA which determines what FC level you need.

2. No. Keep adding acid to maintain the pH in the 7s

3. pH is the easiest the maintain, keeping it in line may slowly lower the TA which will also help. The CH will constantly climb due to evaporation unless you get enough rainfall to keep it lower.

I am surprised you would ever need to raise the TA. With a SWG, it is better to have the TA lower to slow the pH rise.

 

[Divin Dave]

^^^ What Jason says ^^^

The pool guy is telling you wrong. If you want a troubleree pool, then follow the advice here and it will happen.
If you want a headache, follow the pool guys advice.

 

[JasonLion]

The white flakes are from the SWG shedding calcium scaling.

The PH is going up constantly primarily because your TA is way too high, and secondarily because you are trying to keep the PH too low.

Not specifying or testing the CYA is very problematic.

It would be good to test your fill water to see if the CH increase is coming from your fill water or not.

The pool will be much simpler to maintain if you follow our guidelines. The SWG cell will also last longer.

 

[stabguy]

Got it! Thanks for all of the quick advice.

I've only tried to test the CYA one time and got no reading. This was with a Taylor K-2006 kit. The solution was not cloudy at all and the black dot at the bottom of the comparator tube remained clearly visible even when full. Either I performed the test incorrectly or the CYA was very low.

 

[JasonLion]

That means CYA was zero. When CYA is zero you lose chlorine to sunlight very very quickly. It also means you are at great risk of the SWG bringing the FC level up high enough to damage the equipment if the pool were to remain covered for a couple of days.