Total Alkalinity Adjustment...Maybe

[Cleavitt]

I'm just passing the 2 week mark as a new pool owner. So far I haven't had to make any adjustments to the chemestry, but I've been testing regularly with a Taylor K-2005 test kit to get a feel for things. I shocked the pool (to ~35ppm FC) for the first time yesterday evening and this afternoon the TA reading has dropped from 100 before shock to 60 after. To be honest I didn't have any particular reason to shock the pool except my possibly irrational fear of an algea bloom. The FC reading is slightly off the scale for my test kit, but as far as I can tell the FC reading held during the night. It has since dropped to 20 - 25ppm during the day.

Now to get to the point. It appears that I should be adding baking soda to raise TA. However, before I do that I want to make sure that the sudden drop in TA isn't caused by some other temporary condition such as the currently high FC. Based on these test results is it advisable to raise the TA at this time?

7/12/09 15:00
FC 5
TC 5
pH 7.2
TA 100
CH 330
CYA 100

7/13/09 19:00
FC 20
TC 20
pH 7.4
TA 60
CH 330
CYA <not tested>

 

[reebok]

your fear of algae isn't irrational. you'll be getting it soon based on your test results (particularly the chlorine/cya level in your first set of results). what chemicals are you using? (i.e. liquid chlorine, any algaecides? etc.) start reading pool-school/ particularly the water chemistry section.
the high fc can affect the colors of the TA test. there could also be a problem with smaller drops coming out of the reagent bottle (static electricity build up) that you had on the first test but not the second. not sure if the k2005 has that issue or not. you can try wiping the tip of the bottle with a damp tissue between drops.
whereabouts in central fl are you?

 

[Cleavitt]

I'm in Haines City/Davenport.

I'm aware of the FC/CYA issue. It's good to know that my fear wasn't as irrational as I thought. Unfortunately, the previous home owners had what I can only assume was a lazy pool guy taking care of the pool. Maybe he decided to put the pool on "autopilot" when he found out that is was being sold. It seems he was using trichlor tabs almost exclusively (inline feeder set to wide open). The CYA level is quite high, but from what I understand it can only be lowered by draining the pool. I turned the feeder off completely once I realized the CYA level was this high. I plan to use liquid chlorine for the time being. Any advice is welcome.

As far as the TA tests, I'm reasonably sure the first test (100 ppm) was accurate since it matched other tests including a pool store test the previous day. Is it safe to assume that the colors are affected by the high FC? In other words, should I hold off on making adjustments with baking soda at this time?

 

[reebok]

the colors can be affected, the result isn't. it doesn't sound like you had a color change or I think you would have said something. it will be blue/yellow or something instead of red. someone else will be better suited to answer your adjustment question, but it's really not that bad.
the problem you will run into is your cya may be over 100 for one thing (the max is 100 on some {all?} kits), and even if it is 100, you're looking at keeping your fc at 12ppm ideally. you can do it if you want, but it will be easier to take care of imho if you drain some water. and if your cya is over 100, you're going to get algae. then you'll have to drain and fight algae.

 

[duraleigh]

It appears to me that you are in decent shape. I would chalk up the difference in the TA to "one of those things" and not do anything to it. Perhaps testing a couple times more 5-6 days apart will give you affirmation of whichever number is correct. Neither are dangerous. I would make no adjustment until I confirmed the accurate number.

I'm puzzled why you would have 100 CYA in a new pool. That's really too high but tell us why it's in there.

As long as you keep your FC up around 7ppm+ or so, algae will not be a problem. No need to shock if your water is clear and your numbers are in order.

You will not be able to do a successful overnite FC loss test with the K-2005. That overnite test requires a different test not in the K-2005. It's called an FAS/DPD test. It can be ordered seperately from my site or from Taylor directly.

How does your water look?

 

[dmanb2b]

You can leave your TA alone for now, until you sort out the CYA issue, unless your PH starts dipping below 7.2 often. You can retest TA once you get back you your target FC level of 12...unfortunately for you Reebok makes a good point in that your CYA may actually be higher than 100. Not sure if you had rain in FL...I know we've had plenty up north ...but if you can a 50% drain/re-fill will save you a lot of chemicals and frustrations

 

[Cleavitt]

Reebok:

The TA test goes from green to yellow instead of red. I meant to include this info in my previous post, but forgot.

Duraleigh:

The pool is new to me (along with the home), but it was built in 2006 and based on the feeder setting (5.0), Trichlor tabs were used heavily by the previous owners.

I'll plan to drain some of the water in the near future to get the CYA down (to around 50?). Until then, I'll keep the FC well above 7 and keep an eye on the TA level for now. Thanks for the help everyone!

Edit: Oh yeah, the water has been looking good and clear with no strong chlorine odors so far.