help with my numbers

klh66

LifeTime Supporter
Jul 26, 2007
14
Florida
#1
I am a relatively new pool owner and I just want to make sure I am doing my chemicals right. I have a 10K gal. inground pool. I have a cartridge filter that I run 8 hours a day. I live in FL and my pool gets alot of sun during the day. I used to use trichlor pucks in my auto. feed filter but found that my cya was always too high. I switched to the BBB system and I test daily with my Taylor K-2005 test kit. Here are my current numbers:

FC-3
TC-1.5
ph-7.6
TA-60
CH-240
CYA-45

I just emptied my pool of 40%of water yesterday because my cya kept hovering around 80 (from using the pucks). My questions are that I need to add chlorine every single day, at least 41 oz. or more and my ph rises almost daily. Is this normal? My water is crystal clear and has been since it was built and filled in the middle of 5/07. Also, when I do my testing for FC, after adding the reagent, do you read the results immediately or wait a few seconds and let it settle down? My FC reading always goes down a bit after a few seconds. Sorry for going on and on. Just wanted to put all the facts down. Thanks so my for the help and this is an awesome site. I would totally be lost without it and relying on those unreliable pool stores.

klh
 

JasonLion

TFP Expert
Platinum Supporter
LifeTime Supporter
May 7, 2007
37,879
Silver Spring, MD
#2
Either your FC or your TC reading is wrong. FC plus CC equals TC. CC can't be negative, so TC must be greater than or equal to FC.

With a CYA of 45 you should never let FC get below 3 and you should normally aim a little higher than that to have some safety margin.

You probably want TA to be at least 80. Presumably it was higher before you repalced water.

Needing to add chlorine every day is normal. You don't say how large your pool is, but 41 oz a day sounds reasonable.

I wouldn't expect PH to rise with TA that low, but if your TA was higher before you replaced water or you have plaster that is less than one year old then a PH rise is to be expected.

I am not sure about the FC reading changing. The OTO test can do that when CC is high, but I haven't heard of the DPD FC test shifting.
 

klh66

LifeTime Supporter
Jul 26, 2007
14
Florida
#3
Thanks for the quick reply, Jasonlion. I am still having trouble with my FC. I tested my water again and my TC is definitely lower than my FC. Don't know what I am doing wrong. Following instructions to the letter
Any help?

klh
 

Poseidon

Well-known member
May 24, 2007
148
Houston, Texas, USA
#4
klh66 said:
Thanks for the quick reply, Jasonlion. I am still having trouble with my FC. I tested my water again and my TC is definitely lower than my FC. Don't know what I am doing wrong. Following instructions to the letter
Any help?

klh
Of your total chlorine, some of it may be combined chlorine and the remainder will be free chlorine. Ideally you want your total chlorine to be all free chlorine. Combined chlorine of .5 or greater requires super-chlorinating (shocking).
Total chlorine cannot be less than free chlorine or combined chlorine.
Free chlorine + combined chlorine = total chlorine.
There are three methods of testing chlorine.
OTO testing turns the sample yellow. Uses drops. Requires color matching. Supports total chlorine only.
DPD testing turns the sample pink. Uses drops. Requires color matching. Supports free chlorine and combined chlorine.The K-2005 uses DPD testing.
FAS-DPD testing turns the sample pink. Uses powder and drops. Does not require color matching. Supports free chlorine and combined chlorine.

DPD will test the free chlorine first, followed by total chlorine. Subtract free from total and you get combined.