Increase CH for New Pool

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Pikerbu

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LifeTime Supporter
Sep 11, 2012
30
Dallas, TX
Hello,

We have our pool (gunite with pebble Tec) built and filled about 2.5 months ago. I just want to ask for advise if I should be doing more with the following water chemistry

FC = 2.3 (too low for the CYA combination ?)
TC = 2.4
PH = 7.4
TA = 66 (too low?)
CH = 116 (too low?)
CYA = 78 (too high?)

I was told CH will slowly increase since it is a new pool, would you agree? I am really concerned about CYA especially it only has been just about 2 months we start-up. I am using the Tri 3" tab and shocked the pool twice since startup with Sodium di-chlor. When should start partial drain and fill due to high CYA?

Again, appreciate your thought.

Thanks
Hean
Dallas TX
 
Have you read Pool School?

If you have waded in at all you're probably aware that liquid chlorine is the preferred method if not using a Salt Water Chlorine Generator (SWG or SWCG). The pool builder (PB) probably added some startup CYA and then from there the trichlor pucks any dichlor or trichlor shock used would have driven it up also.

Also based on the numbers you gave - I'm assuming you are using a pool store for your tests - don't. They are notoriously inaccurate. If you look in pool school you'll find a link to the test kits recommended here.
 
thanks for comment. I am actually got a LaMotte 2056 ColorQ Pro 7 Digital Pool Water Test Kit. The numbers are also consistent with Leslie's so I think they are accurate.

Should I do something with the CH and CYA at this point given that this is a relatively new pool?

Thanks,
Hean
 
heanchin said:
thanks for comment. I am actually got a LaMotte 2056 ColorQ Pro 7 Digital Pool Water Test Kit. The numbers are also consistent with Leslie's so I think they are accurate.
Click to expand...

:oops: 2nd time today I've assumed that someone had pool store numbers and been wrong. Dang! The ColorQ system has a poor reputation here for not being very repeatable. What type of test does Leslie's use where you are - if they used a drop type test and got similar numbers I guess that's good news. The pool stores are not known for accurate tests either however - many of them use strips and color match tests like the LaMotte system.

Additionally the CYA tests on the LaMotte system are particularly inaccurate at least that's my personal experience. The test system I was comparing against was the professional LaMotte one that has the square prefilled vials and metered measuring tool for filling with pool water that eliminate any user error in preparing the samples. The CYA and TA results were wildly inaccurate and when I had them do 3 tests back to back the values were so far out of agreement with each other I almost laughed out loud.

This is not to discourage you - at least you have a test kit of some type and you are trying to take control of the pool. :goodjob: I'm just warning you the CYA numbers are not particularly known for accuracy and you might want to do some other type of testing for comparison before you assume it is accurate.

heanchin said:
Should I do something with the CH and CYA at this point given that this is a relatively new pool?
Click to expand...

Gunite? I'm not sure. Did your pool builder have specific Calcium Hardness recommendations for the first few months?

CYA - if you trust that number and you don't have an SWG - it's too high for comfort. Are you going to winterize? If so maybe the drain and spring refill will take care of a lot of that.
 
Do not wait to add calcium to increase CH. The CH should never be allowed to increase on its own. Your aggressive water will dissolve calcium from your cement-based finish as time passes, but that is not good for your new pool finish. Your Pebble Tec plaster job will last and look better longer if you balance the water according to a zero CSI as soon as possible. Raise the CH to a minimum of 250 ppm.
 
thank you all...just got the walmart test kit to test CYA. It is showing 80 -100. The ColorQ is showing 86. Sounds like I need to partial drain and fill and get all the chemical right. Not fun especialy only after 3 months of filling..:(
 
We think we find out why my pool CYA went up to 90 from 30 in just over 3 months. We suspect the batch of aquachem 3" tab (regular from Costco) is the problem. On average, I put 2 tab per 1.5-2 week in the feeder and it has been accumulating in feeder with many broken pieces. The last 2 put was last Sun and they are barely "dissolved". We check the water from my house and it is free of CYA so the only souce of CYA is the tab (about 10 -15 tabs total) and 2 aquachem shocks (from Costco) since the pool start-up about 12 weeks ago. Does the Chlorine has that much CYA or do I just get lucky with a bad batch? I will be switching to the BBB method. My question is when I am traveling, I still need to rely on the feeder. So do throw this batch of aquachem chlorine tab away and get another HTH tab from Homedepot?

Appreciate the advice.

Hean
 
All the tablets are the same if they are trichlor ... some have the added bonus of copper ... which is not good.

You can use the bottom of the poolcalculator to see how much each puck is adding ... Although I bet a lot came from the "shock" powder as well.

Lower the cya and Stick with liquid. If you get the CYA low enough then you can use the pucks on vacation.

Posted from my Droid with Tapatalk ... sorry if my response is short ;)
 

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Fortunately or unfortunately I travel on business 1 -2x per month, not long 1 - 2 nights so I do need to come up with a longer term solution. I saw this HTH Super Chlorine tab from Homedept. It says use 1 tab per 10,000 gallons and will last for a week. The "non super" ones requires I think 2 tab per 10,000 gallons per week or less than a week. Do you know if that means "super" one has less CYA or it is just super concentrated. The weight of both seems to be same (around 170g per tab). I guess physically, it is not possible to put more CYA or Chlorine into the same weight.

Thought?
 
Does either one list the percentages of the ingredients?

Are you sure no one added CYA initially?

Edit: see last paragraph - The 15 trichlor tabs are about 120 oz (100) of trichlor and would result in a total CYA addition of 37 (31) ppm. Two 1lb bags of dichlor would only raise the CYA by 9 ppm for a total of 46 ppm. (all based on 13500 gallons from your signature).

The auquachem shock packages were assumed to be 1lb each and dichlor. If this is wrong let me know. I am also assuming the tabs are 3" trichlor weighing around 8 oz each - but that is larger than the weight of 170g you posted so the actual impact if 15 six oz tabs would be lower: CYA would rise by 31 not 37...



- Sent using Tapatalk
 
The following are chemical facts for chlorine independent of concentration of product or of pool size:

For every 10 ppm Free Chlorine (FC) added by Trichlor, it also increases Cyanuric Acid (CYA) by 6 ppm.
For every 10 ppm FC added by Dichlor, it also increases CYA by 9 ppm.
For every 10 ppm FC added by Cal-Hypo, it also increases Calcium Hardness (CH) by at least 7 ppm.

So with 2 ppm FC per day chlorine usage, Trichlor would increase CYA by 36 ppm per month if there were no water dilution. So you could easily go from 30 to 90 in 3 months.
 
chem geek said:
The following are chemical facts for chlorine independent of concentration of product or of pool size:

For every 10 ppm Free Chlorine (FC) added by Trichlor, it also increases Cyanuric Acid (CYA) by 6 ppm.
For every 10 ppm FC added by Dichlor, it also increases CYA by 9 ppm.
For every 10 ppm FC added by Cal-Hypo, it also increases Calcium Hardness (CH) by at least 7 ppm.

So with 2 ppm FC per day chlorine usage, Trichlor would increase CYA by 36 ppm per month if there were no water dilution. So you could easily go from 30 to 90 in 3 months.
Click to expand...
Agreed, but the OP asserts that they have only used 15 pucks and two bags of "shock".


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Yes, 15 8-ounce pucks in 13,500 gallons would be 61 ppm FC and 37 ppm CYA. The bags of shock probably weren't enough to put it over the top unless they were very large bags of Dichlor. The missing 23 ppm CYA would take around 5 pounds of Dichlor. So this doesn't add up. On the other hand, the daily FC usage seems too low if only 61 ppm FC were added from Trichlor. Even at 1 ppm FC per day, 3 months would be 90 ppm FC cumulatively added and that low a chlorine usage seems unlikely if the pool is exposed to sunlight.
 
chem geek said:
Yes, 15 8-ounce pucks in 13,500 gallons would be 61 ppm FC and 37 ppm CYA. The bags of shock probably weren't enough to put it over the top unless they were very large bags of Dichlor. The missing 23 ppm CYA would take around 5 pounds of Dichlor. So this doesn't add up. On the other hand, the daily FC usage seems too low if only 61 ppm FC were added from Trichlor. Even at 1 ppm FC per day, 3 months would be 90 ppm FC cumulatively added and that low a chlorine usage seems unlikely if the pool is exposed to sunlight.
Click to expand...

I agree on all points. One detail that adds to the confusion is that the OP indicated these pucks only weighed 170g which is about 6 oz not 8 as used in the calculation above.

I wonder if a pool service opened the pool and jump started the CYA????


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Pool refill - how to start

Hi, I finally partial drain and refill my pool. My numbers are as follow
FCL 0.03
Tcl 0.16
Ph 7.7
Alk 66
Ch 89
Cya 36

Question is should I start throwing chemical in the pool based on what poolculculator says? Is there a sequence to put chemical?
 
Re: Pool refill - how to start

heanchin said:
Hi, I finally partial drain and refill my pool. My numbers are as follow
FCL 0.03
Tcl 0.16
Ph 7.7
Alk 66
Ch 89
Cya 36

Question is should I start throwing chemical in the pool based on what poolculculator says? Is there a sequence to put chemical?
Click to expand...

That depends. If you plan to follow the shock process - which might be a good idea since you have almost zero FC - then first drop pH to 7.2 and then raise FC to the amount needed for shock levels (14-15ppm). If not then raise FC to the amount recommended on the Chlorine / CYA chart (Min 3ppm; typical target 5-8ppm).

Then I would look to the TA and CH numbers and see what the CSI in poolcalculator tells you. If the scaling index is negative lower than -0.6 say -0.7, then your pool's surface could be eaten away slowly. The opposite is true of the CSI is > 0.6, at these levels excess solids deposit as a scale on the pool staining it.
 
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