PH question in

[mbeck5]

Hi there, thought I would ask a question. TFP since April with lots of your help. Very hot these days in Texas and I am adding about 2 jugs of 121 oz 8.25 Chlorox a day AND adding MA 2-3 times a week. The PH seems to keep drifting up. Are both({PH, FC)situations normal?

Numbers this morning ;
FC- 4.5(will add two jugs)
CC - .5
PH -7.8-8.0
TA - 70
CH - 450
CYA - 45-50

Appreciate your help.

 

[jblizzle]

2 jugs is about 3.8ppm of FC loss per day ... given your climate, I would say that is on the high side of normal ... raising the CYA a little more could help lower the daily addition.

The pH rise is what it is. Any aeration will speed up the rise. As you add acid, it should lower the TA some and slow the pH rise. Although if your top off water is high in TA, then this may not be possible.

 

[tim5055]

Even with the hot Texas sun that sounds like a lot of chlorine. I'm in a hot area with a pool about half your size and I use less than half a 121oz bottle a day.

Have you conducted a Overnight FC Loss Test (OCLT) to rule out organics in the water?

What is your bather load? A bunch of kids in it all day every day eats up chlorine.....

 

[mbeck5]

Your thoughts are appreciated. Will do the OCLT tonight just to check. Our grandkids are on vacation so bather load in the last week has been my wife and I. Added two jugs this morning, waited an hour and tested again, came up with FC of 9.5 and CC of .5. Will post test results and OCLT results in the am. Thanks again.

 

[jblizzle]

Your minimum is 3-4ppm based on your CYA level ... I think you are raising the FC too high and are thus losing more of the FC to the sun.

See my post here for an example: http://www.troublefreepool.com/thre...ommended-level?p=708736&viewfull=1#post708736

 

[mbeck5]

Good morning. The last post was interesting in light of the fact that the OCLT showed no loss. FC was 6.5 last night and is 6.5 this morning. CC was 0 last night and is .5 this morning.

So the numbers are:
FC - 6.5
CC - .5
PH - 7.8
TA - 70
CH - 400
CYA - 50

It was a relatively "cool" day yesterday but the morning FC read was 4.5, added 2 jugs, checked 2 hours later, the FC was 9.5 and at about 9pm the FC was 6.5.
If I understand the information, I should leave the FC this morning at 6.5 and I shouldnt go below the minimum by this evening. Correct? PoolMath tells me the FC
range is 4 to 8. I was even bumping it a little higher to 9 which would appear to be a waste of money. Sound ok or am I missing something?

 

[357]

According to the CYA chart http://www.troublefreepool.com/threads/2177-Chlorine-CYA-Chart your target FC should be 5.7 with a min of 3.7. As I've read FC loss to sunlight is a consistent percentage not a certain quantity. So, overshooting your target would result in more FC loss to sunlight. I'm not sure what the percentage is but say 10% for argument sake. 10% of 9 is 0.9 versus 10% of 5.7 is .57. So if the lost rate was 10% you're losing nearly twice as much FC as necessary, which would be a waste of money.

 

[jblizzle]

I would suggest just using the chart in Pool School and not the one mentioned above as it is less confusing.

The key is to stay above the minimum. Your target will vary depending on your pool to stay above that minimum. I would try leaving the FC at 6.5 today and see where you are at. It might go a little under the min and thus try targeting a little higher the next day to dial it in. I just think 9+ is a little too high.

 

[mbeck5]

I think you are right. I tested the FC yesterday morning at 6.5. By evening it was 5.5 added one jug last night and this morning it is 7.5. Will keep it in the 6.5 to 7.5 range and see what happens. More is not always better!! Thanks again.