Proper CH levels for tiled pool?

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boringforumname

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Oct 15, 2015
25
Kailua, Hawaii
It seems the recommended CH levels have a huge range. I have a tiled pool.

Test results (taylor 2006):

FC - 1.2-1.4 (low because I'm doing a bioactive test to try to lower CYA)
CC - 0-0.2
pH - 7.4
TA - 140
CH - 110
CYA - 110

I'm currently increasing CH with calcium chloride, but I'm not sure how high I should go. The recommended range of 150-400 is very broad. Does a tiled surface matter? Do any of the other numbers matter on where CH should be?
 
You mean the entire pool is tiled? What is your chlorination method - bleach or SWG?

In any event, you should probably have a target CH of 250ppm at a minimum. That will protect the grout in between the tile.
 
boringforumname said:
Yes,the entire pool is tiled. I used di-chlor and tri-chlor
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250ppm CH is the minimum you should target. That will protect your grout.

Dichlor adds 9ppm CYA for every 10ppm FC and trichlor adds 6ppm CYA for every 10ppm FC. If you are doing significant water exchanges (backwashing a lot) throughout the year, it is possible to manage your stabilizer level using solid chlorine products but it is not advised. The excess CYA build up will eventually require you to use higher and higher levels of FC to maintain a sanitized water. Bleach/Liquid Chlorine is better source of chlorine as it does not add any excess stabilizer. As it is right now, your water is dangerously over-stabilized with 110ppm CYA (it should be roughly half that value at most).
 
I missed that you were using BioActive CYA reducer. So you clearly understand that your CYA is too high. I would still recommend the switch to liquid chlorine for pool sanitation as it will avoid the ugliness caused by stabilized chlorine products.

Good luck with the BioActive try, not very many people have reported success.
 
Thank you for all of the advice. I may start another thread about CYA struggles and recommendations. That is going to be a journey in and of itself - not just to reduce CYA but to keep it at manageable levels indefinitely.

As far as the CH goes, 250 would be the minimum recommended specifically for a tiled pool? It seems sometimes I come across recommendations of 150-250 with 250 being the very upper limit. It just seems like the recommendations for CH are very broad and all over the place. Does higher CH have an adverse impact on any other measured requirement? Like if you keep CH above 250, you should also keep pH a little low/high or TA a little low/high, etc.
 
boringforumname said:
Thank you for all of the advice. I may start another thread about CYA struggles and recommendations. That is going to be a journey in and of itself - not just to reduce CYA but to keep it at manageable levels indefinitely.
Click to expand...

If you follow the TFPC Method of pool care, it will be a short journey to perfect water!


boringforumname said:
As far as the CH goes, 250 would be the minimum recommended specifically for a tiled pool? It seems sometimes I come across recommendations of 150-250 with 250 being the very upper limit. It just seems like the recommendations for CH are very broad and all over the place. Does higher CH have an adverse impact on any other measured requirement? Like if you keep CH above 250, you should also keep pH a little low/high or TA a little low/high, etc.
Click to expand...

Calcium hardness does NOT affect other chemistry specifically. Even though pool stores and pool "experts" will make wild claims that things like TDS or CH affect chlorine, the truth and science says otherwise. So, in general, CH can have a large range. You want a minimum amount of calcium in the water to protect your tile grout. Grout is composed of cement which is a calcium based material. So if your water has low calcium hardness then it can strip the calcium out of the grout and weaken it. And this leads to an important topic about the relationship of CH to TA, pH, etc - the Calcium Saturation Index or CSI.

The CSI is the measure of how saturated your water is with calcium carbonate (the primary form of calcium hardness in water). If the CSI is 0, then your water is perfectly saturated with calcium carbonate. If your CSI is positive, then your water is over-saturated with calcium carbonate and there is a driving force for that calcium to come out of solution either by causing cloudiness or by actually scaling out on the tile as calcium deposits. If you CSI is negative, the your water is under-saturated with calcium which mean there's a driving force for the water to absorb calcium either by etching or leeching calcium out of the pool materials.

The important thing to remember is that the CSI is a thermodynamic quantity which simply tells you that a driving force exists. It does not tell you when or how fast either scaling or etching will occur. Typically speaking, if the CSI is between -0.3 < CSI < +0.3, then we say the water is balanced. If you go beyond those limits, then there's the "potential" for scaling (CSI > + 0.3) or etching (CSI < -0.3) to occur. If your go beyond +/-0.6, then your water's CSI is really not good and you're very likely to scale or etch.

PoolMath is your friend! If you add in all your water parameters (using a good test kit like your K-2006), then PoolMath will calculate your CSI for you. For your grouted & tiled pool, I would aim for a slightly negative CSI, somewhere between 0 and -0.2 would be just fine.
 
If I put all of your numbers into PoolMath (assuming 82F water temp), I get a CSI of -0.42. So that means your water is under-starurated and aggressive towards calcium. There is a slight potential for the water to want to leech calcium from the grout. If you increase your CH to 250ppm, your CSI goes to -0.06 which is perfectly fine. Alternatively, you could let your pH go up to 7.6 and then your CSI would be -0.22 which is also fine. At a pH of 7.8, your CSI goes to -0.03, also good.

So, even if you don't want to add calcium (some people prefer not to), then you can still balance your CSI using pH alone. You have a TA value on the high side for your pool. Lowering the TA would make your water more aggressive towards calcium but I would not raise it either as high TA typically leads to pH rise. But again, you have three levers to play with regarding CSI - pH, TA and CH. So this allows you to find a combination of values that best suits your pool water.
 
With regard to the TFP Recommended Ranges, the ranges are designed to give the widest possible latitude to pool owners with respect to water chemistry while still maintaining a properly balanced CSI.

Please note though that the chlorine recommended levels depend on your CYA concentration (see FC/CYA Chart). These values are determined based on what is appropriate for proper water sanitation. So you follow the FC/CYA chart independent from pH, TA or CH.
 

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boringforumname said:
I'm curious as to why some would choose not to add calcium? Are these people living in very hard water areas or some other reason?

Again, thank you to all for help. Some excellent and detailed responses so far. ;)
Click to expand...

Yup, you got it right.

I live in Tucson, AZ. My municipal tap water supply has a minimum CH of 250ppm (that's a best case scenario, other areas of AZ have even higher baseline levels). Even if my pool water started low in calcium, I would not add any as evaporation rates are very high here. I can easily raise my pool's CH 250ppm just by keeping it uncovered and refilling with tap water for a season.

Being in Hawaii, I bet you have high humidity and lots of rainfall throughout the year. High RH lowers the evaporation rate of water and rainfall fills a pool with 0 CH fill water.
 
Whenever I test for CH, after adding the 20 drops of the buffer, and 5 drops of the #11 coloring, I always get pink water, never red. Is this common based on my other numbers given above? Causes?

I don't think I'm getting the fading endpoint problem. As I add and count the drops #12 hardness reagent, the second to the last drop will turn the water purple, but the final drop always turns it blue. As far as I know it has never turned back to purple or back to pink, but truth be told I don't watch it that long before tossing it out. Whatever reading I get will be the same as if I do method #2 where you add 5 drops of the #12 hardness reagent first, then 20 buffer then 5 coloring and the rest of the #12 remembering to take into account the first 5. Either method it's always pink ,to purple on second to last drop, to blue on final drop.
 
That's what I typically see too. My sample will start off pinkish-red, turn purple and then (after many drops) go blue. I typically use the method #2 - adding 10 drops of R-0012 first, then the R-0010 buffer, the R-0011L indicator dye, then more drops of R-0012 until I get the blue endpoint. I also add 1 to 2 extra drops of the R-0011L indicator dye to increase the color strength. Adding an extra drop or two of the dye makes no difference in the endpoint but helps me to see the colors better. Bright outdoor lighting works best for me.

What is your CH value? Mine is currently 775ppm.


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