Calcium Levels

[modog]

I have been using the Pool Calculator. However, the PH measurement is always low. I add the recommended amount but do not get the expected result in change. It is about half of what the calculator indicates. Any ideas?

 

[Melt In The Sun]

Four possibilities come quickly to mind: pool volume, borate level, or TA being higher than entered into the calculator, or acid strength less than the calculator is using (ie. the calculator is set for 31.45% acid and you're using 14.5%).

 

[modog]

Thanks. I bought the stabilizer from Leslies with 99% CYA in it. He said to slowly poor it into the skimmer. I have read the sock trick as well. The container says to dissolve it in water then pour it into the skimmer. If I choose not to do the sock, what is my next best method or safest method for my pool.

Thanks.

Mo

 

[Melt In The Sun]

Wait, I'm confused. pH is low? pH change is less that expected when adding MA (this is what I thought you meant). CYA is low (this is what I think you're asking now).

How long are you giving the CYA to dissolve before you test? It takes a while.

 

[modog]

Sorry for confusion. I have not added the CYA. I was waiting to hear back on the best method other than the floating sock

I had a BTW question on the PH and MA I was adding. For the past 2 years, I was using my builder's measurement of 2 cups per 10K gallons of MA to reduce it .2. I have seen that to be accurate. When I use the PoolCalculator's measurement, I don't get the expected result. I was wondering why this is. I am using the reight strenght of MA that is selected in the measurement. My TA is 85, My CYA is 30. I do have a big waterfall and 2 scuppers. Is this causing it?

 

[Bama Rambler]

The best method for the CYA other than a sock in front of a return is to dissolve it in warm water and pour it in fornt of a return. The skimmer method works but if you have to backwash for any reason you'll lose whatever's still in the filter.

 

[modog]

Ok. I didn't do the sock method. I tried to dissolve it in warm water with no luck. This stuff won't dissolve! I finally did all 2.6 pounds with 2 cycles of the crystals into the skimmer with 2 hours in between. I hope this is ok????

When is it safe to add Bleach and MA? When is it safe to swim?

 

[chem geek]

I do have a big waterfall and 2 scuppers. Is this causing it?

Depending on how long you waited before measuring the pH, it is possible that all of this aeration raised the pH some in that time so the drop in pH from the acid wasn't as much as you expected. If that were what is happening, you would see the pH rising over time anyway, even without adding acid, though the rate of pH rise will slow down as the pH gets higher.

You can reduce the amount of pH rise by lowering the Total Alkalinity (TA) level though yours sounds like it's either low or that you plan on lowering it. Don't expect to keep the pH at 7.3 easily with your waterfall. Next time you add the acid, turn off your waterfall (if you can) and see if that makes a difference in the amount of pH drop.

 

[modog]

Thanks for the info.

Just waiting to hear back on whether I can add my bleach and MA after adding the CYA crystals directly to the skimmer. I backwashed my DE prior to this so I am good. How long before they dissolve? Is there a time to wait before swimming with adding CYA?

 

[Richard320]

Thanks for the info.

Just waiting to hear back on whether I can add my bleach and MA after adding the CYA crystals directly to the skimmer. I backwashed my DE prior to this so I am good. How long before they dissolve? Is there a time to wait before swimming with adding CYA?

Go ahead and add chemicals. The CYA may take a week to dissolve 100%. Just be sure the water is circulating and that you don't add acid and bleach without some time between - an hour or so is fine. Personally, I add acid first, so I don't have chlorine bleaching out my sample.

 

[modog]

Thanks for the help! My pool runs from 9am to 9pm daily. For the CYA to dissolve, can I run it on this normal cycle or do I need to run the pump 24 hours a day for a while? I turned the pump off at 11pm last night and it started back up at 9am today. I will add the bleach and MA today.

Last question...for now My pool sweep is scheduled to run for 2 hours in the morning. Have you found that running it 1 hour in the morning and 1 hour in the evening provides better results? I have a 20' by 40' rectangle pool. Any input would be appreciated.

 

[JasonLion]

Generally, when adding granular/powdered CYA it is best to run the pump for 24 hours straight, and then go back to your normal schedule. Fortunately, nothing particularly bad happens if you fail to do that.

Spreading the run time across two periods about 12 hours apart works better, but usually once a day is enough.