Lower than expected CYA (and FC) -- Newbie

[MoonHen92]

Hi all,

I am new to pool ownership and have done a lot of reading on this site. Its fantastic!

I purchased the TF-100 kit and tested my FC at .5 for two weeks now. I understand that low CYA can cause FC to burn off quick by the sun and that ideal levels at 60-80 ppm for a saltwater pool. However, I am scared to add too much CYA because I don't want to go over 100 ppm since I understand the only way to get rid of CYA is to drain the pool.

On Sept 5, 2014, my CYA tested at about 20 based on the visual "Dot" test last week which can be subjective but even at 20 I could vaguely see the dot. This was after adding 2 pounds of "Saltwater stabilizer" made by Saltwater Series a month ago directly to the skimmer. According to their label, it takes 3.5 lbs to get to 60ppm for a 10,000 gallon pool. Figure I am roughly 6,000 gallons so about 2.1 pounds should get me to 60 ppm. So I decided to add another roughly .5 lbs to see what would happen on 9/5. Today is 9/10 and CYA is testing at about 25 ppm and FC still low at 5. Based on what I have read, the only way to get higher chlorine in SWG is to run pump longer (or adjust CYA to proper level). I currently run 10 hours a day.

So my question is: How reliable is the TF-100 CYA test (I also have less exact "pool check" color strips that show CYA somewhere between 0 and 30-50 but its hard for me to tell exactly. The strips also indicate little to no chlorine). I am hesitant to add more CYA given that I already have about 2.5-3 lbs in a 6,000 gallon pool. According to "pool math" 3 lbs should get me to 60 ppm. Is it possible that adding directly to the skimmer caused CYA to no dissolve? Or is it possible the brand of CYA I bought requires more than indicated on the label? I want to add more CYA to the pool I just am scared I am going to add too much.

I also have the ChlorEase Saltwater Cell which has terrible reviews (I didn't know until after purchasing). Is it possible the cell is just not generating chlorine efficiently? It says it can be used up to 18,000 gallons and the "green" indicator light is on which means the unit is running properly according to the instructions.

Thanks in advance for any advice!
Chris

 

[jblizzle]

Welcome to TFP!!!

The TF-100 has the best of all the tests in it. That is the best CYA test available.

It is possible for the CYA to be slower to dissolve because you added it directly to the skimmer instead of in a sock like we recommend. But I would not think it should take weeks to show up.

What do the ingredients of the stabilizer you bought say?

What is the salt level in your pool? Likely you are not able to get the FC up just because your CYA is too low. Also being left so low could allow algae to start and be consuming the FC as fast as the SWG can make it. You should be supplementing the FC with bleach until you get the CYA and SWG dialed in.

 

[MoonHen92]

Thank you for the detailed and quick response!

All it says on the bottle is "Active ingredient Cyanuric Acid"

My Salt level is about 2710 ppm. Based on the ChlorEase cell this is low. It should be 3200-3700. Can low salt lead to poor FC generation? I was thinking of adding more but the unit flashes a yellow light when salt is low which hasn't happened yet...

My concern is that algae is going to start to form but I am also concerned about adding too much CYA... But it sounds like the CYA test is pretty accurate and its definitely nowhere near 100 based on several TF-100 tests.

 

[jblizzle]

If the SWG thinks the salt level is low, it likely will not generate any FC. I would add another 40 pounds of salt (the SWG should be off for 24 hours after adding any salt).

If you are concerned about algae (which you should be), then why are you not adding FC with bleach?

Trust the TF-100. If the CYA is showing around 30ppm and it has been over a week since you added any, then I would add another 20ppm or so.

 

[SunnyOptimism]

Also, remember that the CYA test is only accurate to about +/- 10ppm. So if you had 20ppm (30ppm is the minimum the melamine turbidity test can read) and you "added a little more to see what happens" chances are you are not going to see it. For example, my CYA was 50ppm and I added three 3" trichlor pucks to my blue floater to raise it up by 7ppm. I could not really see that fine a difference in the CYA test and it still looked like 50ppm or maybe 55ppm depending on the lighting conditions.

So, in the end, you need to trust PoolMath to give you the right values and add what you need. Going over on your CYA from say 80ppm to 90ppm is not the end of the world. CYA will dissipate at a rate of 3-4ppm per month (every pool is different) and you can always have the kids do lots of big splashy cannon balls to get some of the water out.

Reading through your other comments it sounds like both your salt is low (which will make you FC generation low) and you may or may not be running your SWG enough. So until you get your CYA level and salt concentration sorted out, you should do as @jblizzle says and start chlorinating with bleach.

 

[MoonHen92]

Thanks, guys! Very helpful advice. I really appreciate it.

I added 14 oz of 8.15% bleach to hopefully get to 2 FC. Is this something I will need to do daily for now until I get everything else squared away?

 

[jblizzle]

That is not a high enough FC. According to the FC/CYA Chart, you should NEVER let the FC drop below 2ppm (using the non-SWG pool chart). So you should really target 4-5ppm of FC every day until you start to raise the CYA and get the SWG back online.

 

[hAltonJones]

On a related matter, the initial post by MoonHen92, a statement was made saying the only way to lower CYA was to drain the pool. I too am a newbie, but do have (1) a chemical engineering background and (2) a propensity for asking stupid questions.

If the test for CYA involves adding melamine which cause the water to become turbid due to the fact that melamine causes CYA to precipitate out, why couldn't you simply add melamine to the pool and let the filter system remove excess CYA?

 

[Richard320]

On a related matter, the initial post by MoonHen92, a statement was made saying the only way to lower CYA was to drain the pool. I too am a newbie, but do have (1) a chemical engineering background and (2) a propensity for asking stupid questions.

If the test for CYA involves adding melamine which cause the water to become turbid due to the fact that melamine causes CYA to precipitate out, why couldn't you simply add melamine to the pool and let the filter system remove excess CYA?

Use the search box for Melamine and you'll find out.

Apparently, in the quantities required, it's not economically feasible, and it doesn't filter out well.

Unless you're looking at water restrictions with expensive penalties including flow restrictors placed on your meter at your expense, replacing water is cheapest.

 

[Griswald]

Before I started the TFP method, I hsd 1.0 FC and 10 CYA. Never had any problems, but I realize Im just lucky. In order raise my FC, I added bleach, enough to shoot past my mark. After that, the SWCG was easily able to hold that new level, it just couldn't get to that level by itself.