Conflicting CYA Advice

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honeill14

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LifeTime Supporter
Aug 2, 2014
18
Hopedale, MA
Hello, I am new to this forum so I hope I'm doing this correctly. Here are my pool details;
In ground pool built in 2005, Vinyl, 18 x 39, SWG Aqua T-Cell 15 (currently set to 60% chlorination), timer is on for 12 hours and the pool probably gets about 8 hours of direct sunshine each day. Pool is about 24,000 gallons and has a Hayward Pro-Series sand filter.

I'm in the Boston area and last season my pool store gave me some very bad advice, which lead to my kids not being able to use the pool for the last 3 weeks in August and set me back almost $200 in chemical costs (yes they persuaded me that a high phosphate level was my problem). This season I vowed to become more knowledgeable about my pool, even though Chemistry was never one of my strengths. So far it's been a great summer and the pool clarity looks very good.

Having read some of your advice on this site I wanted to raise my FC level to between 3 or 4 , as is recommended for SWG pools. Ideally I should be running my SWG at between 40/50%, right now it's at 60% and just keeping up as FC readings in the a.m. are low having been off all night. My local pool store said my CYA needs to come up to 70 or 80 to make that happen. Again having read the posts about the mythical chlorine lock and suggestions that for SWG pools the ratio between FC and CYA should be 5%, I'm concerned that by adding more conditioner/stabilizer I will need to increase my SWG% higher to satisfy the chlorine needs.

My goal is to keep my pool in it's current condition without working my SWG working too hard, it's still the original installed in 2005. What do you recommend I do to raise my FC level, so I don't have to keep raising the SWG% or running Super chlorinate too often?

Latest readings;
FC = 2.47
PH = 7.8
Alk = 37
CYA = 61
Salt = 3100
Pool temp averages between 79-82F (I have a heater but only run it at beginning and end of season so it's not on at the minute).

Cheers!
 
honeill14 said:
Hello, I am new to this forum so I hope I'm doing this correctly. Here are my pool details;
In ground pool built in 2005, Vinyl, 18 x 39, SWG Aqua T-Cell 15 (currently set to 60% chlorination), timer is on for 12 hours and the pool probably gets about 8 hours of direct sunshine each day. Pool is about 24,000 gallons and has a Hayward Pro-Series sand filter.

I'm in the Boston area and last season my pool store gave me some very bad advice, which lead to my kids not being able to use the pool for the last 3 weeks in August and set me back almost $200 in chemical costs (yes they persuaded me that a high phosphate level was my problem). This season I vowed to become more knowledgeable about my pool, even though Chemistry was never one of my strengths. So far it's been a great summer and the pool clarity looks very good.

Having read some of your advice on this site I wanted to raise my FC level to between 3 or 4 , as is recommended for SWG pools. Ideally I should be running my SWG at between 40/50%, right now it's at 60% and just keeping up as FC readings in the a.m. are low having been off all night. My local pool store said my CYA needs to come up to 70 or 80 to make that happen. Again having read the posts about the mythical chlorine lock and suggestions that for SWG pools the ratio between FC and CYA should be 5%, I'm concerned that by adding more conditioner/stabilizer I will need to increase my SWG% higher to satisfy the chlorine needs.

My goal is to keep my pool in it's current condition without working my SWG working too hard, it's still the original installed in 2005. What do you recommend I do to raise my FC level, so I don't have to keep raising the SWG% or running Super chlorinate too often?

Latest readings;
FC = 2.47
PH = 7.8
Alk = 37
CYA = 61
Salt = 3100
Pool temp averages between 79-82F (I have a heater but only run it at beginning and end of season so it's not on at the minute).

Cheers!
Click to expand...
Welcome! :wave:

I just have to ask: Where did you get those test results? Are they from your own tester, or are you still relying on the pool store?
 
Yes, I am relying on the pool store electronic test equipment for the current results, why do you ask?

I also use test strips. I have two sets of strips; Insta test and Aqua Check and they don't really match when I compare them.

Thanks.
 
Well, there you go. Two strips that don't match ... that explains why we do not trust test strips. We also do not trust pool store testing, especially if it is computerized ... do you know when and how it was calibrated?
 
One of these Test Kits is what we recommend for testing your water.
Grab yourself one as it will be the best investment you can make for your pool. Plus if you want accurate advice from us we need accurate test results to base our advice on. Plain and simple !!��
 
Good job !! Testing is easy. You'll get the hang of it. There are you tube videos on all the tests. Watch them while the test kit is getting shipped. When it comes post up a full set of results for us to have a look see. ?
 
Welcome to TFP from another newbie :wave:

One thing you need to keep in mind is that low CYA can be just as bad as high CYA in terms of FC level. Too low, and the UV burns up all your FC, too high and the CYA buffers all of the FC generated and keeps it from being effective.

-----EDIT------

Additional add-on thought that others have mentioned - CYA is one if the pool parameters that pool stores are NOTORIOUSLY bad at measuring. They can sometimes match you in FC/CC and pH but CYA, TA and CH are typically way off or, worse, inconsistent. So your CYA of 61 might not be 61.

----END-EDIT------

Since your reported CYA level is close to spot-on then you might have to consider that your SWG is just getting old, especially considering it is now 9 years old.

Have you cleaned the cell recently?
 

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I have two concerns. First, 3-4 is the target or "lowest" FC for your pool. I shoot for 5-6 to ensure I never drop below 3.

Second, you said your FC drops overnight. This could be indicative of a problem. When does your pump and SWG turn off at night, and when does it come back on?
 
Test kit arrived yesterday and I ran the tests this morning. Here are the results from the TF-100 kit;
CYA = 38
CDP=1
CC=0
TA=50

Daily tester;
Chlorine was in the 1-2 range.
Ph was 7.2

Based on these results and other information on this site it looks like I need to do the following;
Bring my Ph level up to the 7.5 range.
Conditioner to 60
TA to 70

Any suggestions on how much of each to add and the order?

Thanks again.
 
Give the pool math page, linked at the top of every forum page, http://www.troublefreepool.com/calc.html

Enter your pool volume at the top, type of construction, guidelines/method chosen (TFP) at the bottom. Then enter your current parameters in the left column and desired levels in the right column. Recommendations are provided.

Happy swimming. You are on the right track.
 
PH is okay for now. TA should be all right as well. You should get the FC up a bit to 4 or 5 with a CYA of 40. See this chart. http://www.troublefreepool.com/content/128-chlorine-cya-chart-slam-shock

If you don't want to strain the SWG, you can manually add the required amount of chlorine to get the FC to the right level. Then hopefully the SWG can maintain that.

Then you can get some more stablizer in the pool to get the CYA to 60-70.
 
I too run my SWG during the day, from 11-7PM. As a rule, when I test at night at 7PM and then again the next morning at 7-7:30, I expect 0 FC loss overnight. While it is acceptable to have a .5 ppm loss, as a rule, I see 0.0 FC loss.

- - - Updated - - -

Actually, the rule is that overnight FC loss < 1.0. Since I don't use the .2ppm scale, instead I use .5 ppm sample size, I use .5 as my check point.
 

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