Calcium Hardness

[chem geek]

To get from 200 CH with fill water to 550 CH after evaporation and fill, it would take 550/200-1 = 175% of your pool water volume to achieve that. That's an awful lot of evaporation, but perhaps is what is happening in your case. If you have a bucket of water next to your pool, you can see how quickly the water evaporates. Assuming a 4.5 foot average depth for your pool, you would need evaporation of 4.5 * 1.75 = 7.9 feet of evaporation per year or 0.26" per day (actually double that or around 0.5" per day since there isn't much evaporation in the colder months).

Richard

[mas985]

95" is less than what parts of Arizona and Texas experiences over the year so it really depends on where you live. Check out this Link for where you live to get an estimate.

I experience about 60" with is a full pool volume over the year so my CH almost doubles over the year.

EDIT: I should modify this some by saying that with a pool cover, you can greatly reduce the amount of water lost and thus the buildup of calcium.

[chem geek]

What a great link! I've bookmarked that one! Thanks.

[ndillon2]

Cisco,
Does your salt cell clog with scale build up? I have the same issues with CH and PH rising quickly. I go through 2-5 gallons of acid per week just to keep the PH down around 7.2-7.5. The SWG cell clogs with scale every day. I have to remove and clean with a power washer. MY Ch is also 600+ and there are scale flakes that come out of the return lines into the pool. I have considered bypasing the SWG as it is more problem than normal maitenance. However, I just feel like I am missing something and should not give up on it. Any help is appreciated. Thanks

[Ciscokid]

ndillion2,
I don't have a problem with scaling on the Cell.( other than the normal build up.) I clean it maybe once a month or so. Other than my CH being 550 all other chemicals are perfect. The pool itself is crystal clear.
Post all your chemical readings and maybe someone can better help with your problem.
Based on all the help I am going to raise my borates to see if it will slow my PH rise.Also I may airate the pool and get the TA down to 80. Thank you all for you information .

[chem geek]

ndillon2,

It sounds like your've not only got high CH, but also high pH and TA and that combination will often lead to scaling. The solution is most likely to lower your TA significantly. If you post your numbers (including FC, CYA and temp) we can see if this is what is happening and propose a solution.

Richard

[ndillon2]

I tested with a drop kit and strips
FC is currently zero as the SWG has been clogged, not producing. I bypassed it yesterday and supplemented with bleach. I will continue until the cell is replaced
PH = 7.5 I have been maintaining at that level with approx 1/2 gal acid per day
TA = 80 been fairly steady for last couple of months
cya = 70 (adjusted 3 weeks ago from 40
CH = 1000 (test strip test)
temp = 80-84

I have had this problem for two years, constantly battling the SWG clogging abut every two days. I also have the scale ring around the perimeter on the tile. Assistance appreciated.

[chem geek]

If your Calcium Hardness (CH) were truly only 1000, then with a TA of 80, CYA of 70 and pH of 7.5 (and assuming 3000 ppm salt), your saturation index is only +0.14 which isn't high enough to produce the kind of scaling you are seeing. However, maybe your test strip is not able to measure super-high CH levels. However, you'd probably not see scaling unless your CH was closer to 2000 ppm or more. That would explain your situation.

Do you know the CH level of your fill water? Can you measure that separately and let us know? It would be better if you had a more accurate drop-based test for measuring the CH level especially since it is so high (i.e. a Taylor K-2006 test kit or Leslie's Chlorine FAS-DPD Service Test Kit or for just the CH test, the Taylor K-1770 here where you can use the 10 ml sample so each drop will be 25 ppm). As for what to do, that will depend on your fill water so let's get those results first.

Richard

[ndillon2]

Fill water CH is 200 (test strip)

I tested everything today as follows:
CL = 1
PH = 7.6
CYA = 50 (added stabilizer to bring up to 80)
TA = 80
CH = 1000 (test strip)
CH = 460 (pool store test).

The pool store recommended AllClear Stain and Scale for the hardness
I cleaned the salt cell yesterday and this morning it was fully clogged with scale. Flakes continue to come out of the return lines and congreagte on the step just below the return.

Is it possible that scale has built up on the walls and as it breaks up and is sucked through the filter it then clogs the salt cell?

[waterbear]

There are NO test strips that I know of that measure calcium hardness. They measure TOTAL hardness (magnesium and calcium)!