Can you check my numbers before I close

[Johnny B]

10/19/2012
pH 7.6
FC 4
CC 0.5
TA 40
CH 350
CYA 30
borates 15
55° F

I am ready to close for the season and would like to be sure you guys agree with what I write below. My main concern, because it has been a problem in a prior year (and still is I guess but just because I haven't re-plastered the pool, it is just a little unsightly and during the season I can keep everything in line) is to try to avoid or minimize further calcium scaling.
During the season a few months ago, I discovered that a TA of 50, pH of 7.6 was better to keep things balanced with a CH of 350.
So the TA has dropped from 50 to 40, that's to be expected and I was going to bring that up to 50, but that results in a CSI of unbalanced, but if I get TA to 60 that results in a balanced CSI, even if the pH gets to 8.3 (my problem in a past winter was the pH got too high for too long over the winter, I learned my lesson and do test and treat things during the winter now).
I have been successful targeting a CYA of 45 and so I will raise the CYA from 30 to 45

So in review, I want to raise the TA to 60 & the CYA to 45, then shock before closing and allowing the FC level come down per the TFP recommended closing procedure, along with algaecide & the rest of the things.

Or do you want me to fiddle/raise w the TA some more, which I have not done in the pool calculator? Pretty easy to add baking soda over the winter to keep TA it in the 40-50 range.

This CSI can get a little tricky so I was hoping you guys could improve my game plan or okay it.
Thanks

 

[BoDarville]

Johnny B:

My main concern...is to try to avoid or minimize further calcium scaling.

To help avoid further calcium scaling, you want to keep your CSI slightly negative. Now on to your numbers...

• • CH, CYA, & Borates look fine. Wouldn't mess with those.

• • As for pH & TA, although you may have found that a TA of 50 and pH of 7.6 worked well for you during the swim season, it may not work as well during the off-season taking into account the colder water.

One question I have is, how cold does your water get at its coldest? Colder water is considered more acidic in terms of the CSI calculation. For example, inputting your pH target of 7.6 and TA target of 60 along with your other numbers into the pool calculator at 55°F with closing gallons of 18,654, I get a CSI of -0.29 (Balanced). However at 37°F (the coldest my water has ever been in DFW), those same numbers make the CSI -0.47 (Potential to become corrosive to plaster).

So what I would do is consider raising TA to 70 and keep pH between 7.6 and 7.8. Using my 37° example and inputting a TA of 70 and pH of 7.7 while holding your other numbers constant, the CSI would be -0.29 (Balanced). Those same numbers at 55° still show a balanced and slightly negative CSI of -0.12. Your CSI remains negative at these numbers until water temp hits 67° when CSI hits 0.00. At that time, it will be getting close to opening and you could adjust your TA back down towards 50 since that appears to have worked well for you this past swim season.

As for FC, I would give a final dose of chlorine to get FC the level up a bit (say around 10-13 ppm FC). You could also (optionally) add a start-up (maximum) dose of Polyquat 60 algaecide per label instructions. If you do this, wait until the FC comes back down about half way to its normal levels before adding the Polyquat 60. Then you are ready to close it up.

 

[Johnny B]

Johnny B:

My main concern...is to try to avoid or minimize further calcium scaling.

To help avoid further calcium scaling, you want to keep your CSI slightly negative. Now on to your numbers...

• • CH, CYA, & Borates look fine. Wouldn't mess with those.

so glad I asked, thanks!

• • As for pH & TA, although you may have found that a TA of 50 and pH of 7.6 worked well for you during the swim season, it may not work as well during the off-season taking into account the colder water.

exactly what I was thinking

One question I have is, how cold does your water get at its coldest?
As cold as the water gets is probably 40F, we do get snow some years so it probably gets to ~ 33F, never saw ice in the pool, probably the “routine-prolonged coldest” is 38F?. Some in Charlotte never close their pool
Colder water is considered more acidic in terms of the CSI calculation. For example, inputting your pH target of 7.6 and TA target of 60 along with your other numbers into the pool calculator at 55°F with closing gallons of 18,654, I get a CSI of -0.29 (Balanced). However at 37°F (the coldest my water has ever been in DFW), those same numbers make the CSI -0.47 (Potential to become corrosive to plaster).

So what I would do is consider raising TA to 70 and keep pH between 7.6 and 7.8.
I will raise the TA to 70. It's a challenge to keep pH 7.6-7.8 but I'll have to try harder/ test more often. Testing w the cover on is a real PITA & time consuming & back breaking etc not to mention circulation is comprimised- a sump pump only, have to greatly dilute the chemicals & dispense over long periods of time
Using my 37° example and inputting a TA of 70 and pH of 7.7 while holding your other numbers constant, the CSI would be -0.29 (Balanced). Those same numbers at 55° still show a balanced and slightly negative CSI of -0.12. Your CSI remains negative at these numbers until water temp hits 67° when CSI hits 0.00. At that time, it will be getting close to opening and you could adjust your TA back down towards 50 since that appears to have worked well for you this past swim season.
That is a great suggestion. I watch the temp in March, as soon as it gets ~ 58F I open, I don't want the cover on at 60F+ .

As for FC, I would give a final dose of chlorine to get FC the level up a bit (say around 10-13 ppm FC).
no need to take it to shock level? why was/is that in the TFP closing suggestion? I'm happy to take it only to 10-13, FWIW,my shock level on the calculator said FC 16
You could also (optionally) add a start-up (maximum) dose of Polyquat 60 algaecide per label instructions.
I have in the past & will do again
If you do this, wait until the FC comes back down about half way to its normal levels before adding the Polyquat 60.
I remembered that but thanks for mentioning it!
Then you are ready to close it up.

I'll await your or others reply. Thanks again, I REALLY appreciate it.

 

[BoDarville]

Johnny B:

Please excuse the delay in responding. Just getting back from a weekend in Houston.

As for the shock levels, there are slight discrepancies between the Pool Calculator & the Chlorine / CYA Chart in Pool School. At a CYA level of 30, the Chlorine / CYA Chart states a shock level of 12 ppm whereas the Pool Calculator states 13. BTW, I double-checked the Pool Calculator and, for a CYA level of 30, I'm still getting a Shock Level of 13. In any event, if your final dose of chlorine is reasonably close to that range, I'd call it good to go.

As for the Polyquat 60 algaecide, the active ingredient is: poly [oxyethylene (dimethyliminio) ethylene (dimethyliminio) ethylene dichloride]. Look for a 60% concentration of that ingredient to make sure you are getting the right formulation.

Sounds like your pool is in good shape overall and you have a good plan for closing it. I would expect that you will be fine come spring. BTW, my pool had a calcium ring around the waterline in both the pool & the spa when I bought the house. Since switching to BBB just over a year ago and becoming educated on pool chemistry management, that calcium ring has disappeared from the pool and is fading fast in the spa.

 

[Johnny B]

Johnny B:

BTW, my pool had a calcium ring around the waterline in both the pool & the spa when I bought the house. Since switching to BBB just over a year ago and becoming educated on pool chemistry management, that calcium ring has disappeared from the pool and is fading fast in the spa.

I wasn't so lucky with my calcium scaling. I tried many things and none of them worked. The acid wash was the only possibility I did not try (although I tried concentrated acid underwater unsuccessfully ); that reduces the plaster life by a few years and I'm pretty sure I am a few years away from a new plaster anyways so I just put up with the unsightly scaling

. I goofed on the FC because I was putting in a different CYA.

thanks again for your help

 

[BoDarville]

Keep the faith regarding the calcium scaling. It is admittedly not a fast process by any means, but with good chemistry balance (pH & TA in particular) the calcium scale will gradually diminish from the current levels especially since your current CH is within the recommended range for a plaster pool. One thing that may have helped speed this up for me is that I keep my pool open year-round. During the 4-5 months it is too cold to swim, I still routinely test pH & TA (along with FC) and adjust as needed to maintain a good balance which for me is a slightly negative CSI.