Not enough MA vs. pool calculator

[modog]

I have been adding the pool calculator's MA measurement to my pool; however, I never get the PH down to the desired level based on the amount it tells me to add. It seems I have to add double the MA to get the desired affect. I did check the bottles for the correct strenght and plugged it into the pool calc. With a large overflow waterfall from the spa into the pool and 2 scuppers, could this be the cause of my struggle? I tend to lose TA quickly as well. I run my pump from 9am - 9pm and brush exactly once a week. I am in Dallas, TX.

I had this question on a calcuim topic and thought I should move it to it's own post. Any help is appreciataed. Here are my current levels.

FC - 5
CC - 0
CYA - 40
PH - 7.6
TA - 70
Caclium - 410

 

[modog]

Another question...how much MA can I add at a 1 time for a 28K gallon pool? When can i re-add? My builder always said 1 pint for every 10K to lower it .2. The pool calc is different.

 

[JasonLion]

Depending on how long you wait between adding the muriatic acid and when you next test the PH, the PH might have gone down the correct amount and then have come back up before you had time to test it.

Somewhat high TA plus aeration will raise the PH level. Adding acid to get the PH back in line will lower both PH and TA. The more aeration you have, the lower you need TA to be before things will stabilize. If you have a really large amount of aeration, it becomes quite difficult to get things stabilized.

The first thing to try is to let the TA go down to 60 and see if PH will stabilize around 7.8, and see if that helps at all. The next thing to try would be to add borates to the pool and then let TA go down to 50 and then see if things will stabilize.

 

[Richard320]

Maybe your pool is bigger than you think?

 

[modog]

Thanks for the tip. I was previously trying to keep TA at 90-100. Now I will make sure it is 60-70. Is it safe to add more than 1 round of MA to the pool in a day? If the builder was off on my pool size, do you have a way I can measure it?

 

[Butterfly]

Well, one gallon of bleach will raise 10,000 gallons of water approximately the percentage of the bleach in FC (i.e, one gallon of 6% ultra bleach will raise 10,000 gallons approx. 6 ppm FC).

 

[JasonLion]

There are two ways to figure out the pool size. One is to measure the pool and do some calculating, the other is use chemical additions to adjust an initial size estimate over time. Start with some estimate of the pool size. Add whatever chemicals you need to add based on the Pool Calculators calculations and see if you are consistently getting higher or lower results than you anticipated. If the results are consistently higher than expected, lower your estimate of the pool size. If the results are consistently higher than expected, raise your estimated pool size.

 

[modog]

According to my CYA, I need to have the FC from 3-7. So I put enough bleach to bring it to 5. I have noticed that every Friday it is back at 0. So is 1 week a normal time frame to lose all FC in Texas. It is in the 90s and my CYA=40, TA=60,ph 7.5.

Also, I will try to re-calc my pool size using chemical analysis. Any other method you can recommend?

 

[dschlic1]

Richard (Chem_Geek) has stated that the pH calculations are inexact. On my pool I have found that I need 1.5 to 2 times the acid to achieve the desired pH change. However they are a good starting point.

 

[benavidescj]

I have a similar issue. My pool is also 28k and has a waterfall that is about 8 ft across. My TA is around 70 and I constantly have to add MA, about 1 quart per day to keep the Ph down. JasonLion, I have borates (50 ppm) in the pool and was wondering how low the TA can go and what the side effects would be if it got lower?

 

[modog]

Thanks. What about my question regarding the FC going from 5 to 0 in 1 week. Is this normal?

 

[Melt In The Sun]

modog, yes that is normal. Most pools lose 2-3 ppm/day. You'll need to add chlorine more than once a week!

 

[svenpup]

Thanks. What about my question regarding the FC going from 5 to 0 in 1 week. Is this normal?

You should measure pH and chlorine daily and adjust as needed. You should never let your FC go to 0 (or below the minimum level for your CYA for that matter).

..and yes, losing 5ppm FC in a week is normal, especially in the Texas sun.

 

[modog]

Thanks for the info.