Multiple balancing and diagnosis questions from a new pool owner

[Phlow]

I've just taken over the chemical maintenance of my pool from the builder, and due to a couple of leaks around the tile the water was dropping over an inch a day. So I was having to fill it every other day.


It has been real fun (and pricey) keeping the pool balanced. I've had to add salt, CYA, calcium chloride and muriatic acid to varying degrees recently.


My TA and pH were good originally, so I started with CYA, then did calcium chloride a couple days later. Then I somehow lost 300ppm salt, my pH shot up to 8 and my TA hit 110.
So I've been adding muriatic acid for a couple days. And finally today I added 80lbs of salt.


So, getting to my questions:


1) Is it safe to add chemicals to the pool in the same day? Certain ones that are ok? Others not?
2) I started with FC:2 @ CYA:0, then I added 12 Lbs of CYA, the next day FC:8.5 @ CYA:80, next day FC:10 @ CYA:75, 2 days later FC:14 @ CYA:55. What factors could cause that level of FC rise, given the leak and CYA drop?
3) Related to last question, how do I know what % to keep my SWG at? I suspect that maybe I need to lower it from the 50% it's set at, due to my spike up to FC:14.
Is there some calculation involving filter run time (with VSP %'s and timers, swimmer load, UV index, etc)? I can see there would be a lot of variables, but I'm looking for anything that is beyond a guessing game.
4) Surely someone has come up with a better CYA-adding process than squeezing an old tube sock in a skimmer for an hour or more?
5) Muriatic acid is not nearly as effective on my pool as PoolMath seems to think it should be. What it said would drop my pH down to 7.0 only dropped it to 7.5, and only took TA down from 100 to 90. I verified its 31.45% from Home Depot and using that setting. Is this most likely caused by my new plaster?
6) I just read a post saying that the pH reading will be inaccurate with FC about 10. Does that apply to the drops as well as the pH meter device?


Thanks for any info!


Jay

 

[jblizzle]

1) Yes. Just leave 15-30 minutes between chemical additions. And some could be added closer to together
2) Higher CYA better protects the FC from the sun, and if your SWG was left at the same setting, then the FC will climb
3) Trial and error is really the only option. There is a spreadsheet that will estimate the amount of FC that your SWG will add for a given amount of time (somewhere on the forum )
4) Well, you could hang it in front of a return jet and squeeze it there. Using the sock ensures you know when it all dissolves
5) Did you have all the other parameters in PoolMath set? Specifically the TA?
6) The pH meter may not be as impacted by the higher FC, but I am not 100% on that.

 

[mknauss]

SWG Run Time Calculator

To answer #3. Download the spreadsheet.

 

[needsajet]

1) Is it safe to add chemicals to the pool in the same day? Certain ones that are ok? Others not?
2) I started with FC:2 @ CYA:0, then I added 12 Lbs of CYA, the next day FC:8.5 @ CYA:80, next day FC:10 @ CYA:75, 2 days later FC:14 @ CYA:55. What factors could cause that level of FC rise, given the leak and CYA drop?
3) Related to last question, how do I know what % to keep my SWG at? I suspect that maybe I need to lower it from the 50% it's set at, due to my spike up to FC:14.
Is there some calculation involving filter run time (with VSP %'s and timers, swimmer load, UV index, etc)? I can see there would be a lot of variables, but I'm looking for anything that is beyond a guessing game.
4) Surely someone has come up with a better CYA-adding process than squeezing an old tube sock in a skimmer for an hour or more?
5) Muriatic acid is not nearly as effective on my pool as PoolMath seems to think it should be. What it said would drop my pH down to 7.0 only dropped it to 7.5, and only took TA down from 100 to 90. I verified its 31.45% from Home Depot and using that setting. Is this most likely caused by my new plaster?
6) I just read a post saying that the pH reading will be inaccurate with FC about 10. Does that apply to the drops as well as the pH meter device?

Congratulations on the new pool!

1) Yes, just keep the pump running, and wait 15 minutes between additions. Never mix chlorinating liquid and acid.
2) Could be that your SWCG is turned up too high. Try turning it off for a few days and let the FC drop. The CYA would only drop slowly, so that may be just test variation, but in any event, always wait a few days after an addition before testing CYA because it's slow to dissolve. In a brand new pool, your best estimate of CYA is just the math of CYA divided by water volume. A possibility to consider is that if you backwashed before waiting a week after a CYA addition, then some of the CYA can be backwashed out of the filter.
3) No real formula because of the high variation between pools, but for round numbers, 2 to 4 ppm FC per day is an approximation. If you mention the SWCG model, we can calculate what that is in run time, approximately. Reality is that people start a bit high and then dial it down. In your case, let it drop to around 6-8 by turning it off, and then start dialing it in.
4) That's the best method. Thankfully it's only needed occasionally
5) When a pool is new, it adds TA fairly quickly. Dropping to 7.0 is not necessary and could speed up the release of alkalinity from the pool surface. Try just dropping it to 7.5. Note that the "Effects of Adding Chemicals" and the pH section in PoolMath include comments about the approximate nature of pH prediction, and then only within certain boundaries.
6) The pH meter is probably still as good as it can be around FC 14. Best bet is to let your FC drop and then use the drops. There's no reason other than algae removal to be above 10 anyway, and when we remove algae, we just drop the pH before the process and then ignore pH during the process.

Sounds like you're picking up the principles of pool care really well. Have fun with the pool

 

[Phlow]

Thanks all.

1) Good to know I can speed up the process a bit.
2) Good point about it climbing due to CYA protecting the chlorine. Should have connected those dots myself.
3) I had the SWCG off today while I added salt, so I'll just keep it off till about FC:6 as suggested and then maybe drop the SWCG% to 30%, see how it goes. The SWCG is a T-Cell-940.
4) That's unfortunate. I guess since the builder didn't originally add CYA, and then my leaks lost a bunch, I've had to do more of it than typical.
5) I did have the parameters set, yeah. Interesting info about dropping to 7.0 speeding up TA release. Wouldn't have guessed that. I hadn't been using the "Effects of Adding" section, just the overview detail pages for each test. Good to know!
6) Yeah, I wasn't trying to get FC that high. It only recently spiked up the way it did. I will keep that in mind though. I had read that lowering pH is helpful there... which of course makes sense.

Thanks for the link to the Excel spreadsheet. I'll have a look.

Yeah, I've been doing my homework, and I'm a software engineer, so I love debugging problems and understanding the complexities. Thanks!