CYA misunderstanding

[robdac]

As a first time owner of a new to me pool I'm realizing I had a basic misunderstanding of CYA or stabilizer. I thought it was similar to salt in that salt does not normally leave the pool water unless it's diluted in some fashion such as backwashing or draining and refilling of the pool.

I found this great web site early on and was lucky enough not to have my mind polluted by pool store advice. I love the idea of knowing exactly what you're adding to the water and more importantly why. Because of this and reading the high CYA horror stories I've never used pucks of any type. Over the last two months of regular testing with the TF Test Kit I've realized that a little CYA is required on a weekly basis to keep my CYA level appropriate to my pool. The advice here of using the sock in the skimmer basket has been great.

It seems to me now that CYA additions are required on a regular basis to protect chlorine and appropriate levels must be maintained through proper testing. Unfortunately, many people using pucks think they are the Ronco (set it and forget it) of pool care leading to excess CYA. The excess CYA then prevents the remaining chlorine that is in the pool from doing it's job leading to a swamp. If I have an improper understanding of CYA please continue to educate me.

 

[JasonLion]

Something is wrong if you need to add CYA weekly. CYA mostly behaves like salt, not going down unless you replace water. You will lose just a little bit of CYA to breakdown due to chlorine over the course of an entire season, and CYA can sometimes go down quickly when FC goes to 0. But in normal operation there shouldn't be enough CYA loss to have to adjust it anything like weekly. We normally recommend testing CYA monthly, and it is rare that you would need to adjust it more than once a season.

 

[robdac]

Here's what I've added (all dry CYA added by volume) to the pool so far this year:
3/10 measured at 60 then added 20 oz
3/17 measured at 65 then added 8 oz
3/25 measured at 68 added nothing
4/04 measured at 70 then added 7 oz
4/12 measured at 60 added nothing
4/19 measured at 50 then added 32 oz
4/26 measured at 65 then added 15 oz

 

[JasonLion]

Something is clearly very wrong. But nothing here suggests what it might be. The more obvious possibilities include: adding something you think is CYA but actually isn't, bad CYA test reagent, high rates of water replacement, or FC levels going to zero (combined with some bad luck with soil bacteria).

 

[jtaves85mcss]

+1^ on something being up with dropping CYA numbers.

What level of loss are you experiencing and how much CYA are you adding? I see you added that in post 3

From the extended test instructions sticky (by JasonLion): "The precision of the test, when done correctly, is around plus or minus 15 for levels up to 90 and plus or minus 30 for levels between 100 and 200."

That variability brings in some possible difference from test to test, but once you have practiced you should be able to get repeatable results in each test session, with some slight variation on the next test (three to four weeks later). Consistency in your test process/methods and lighting should be reviewed.

Then check whether you have something like an auto fill that is malfunctioning or are using techniques like vacuuming to waste, which would result in water replacement.

Adding: Water loss and replacement is my first guess and as noted above, your product may not be regular stabilizer. Using poolcalc, the first addition of 20 ounces should have taken you from CYA 60 to 74, but you only got an increase of 5 points.

 

[pooldv]

I noticed the pool is in FL and it is a rainy spring, at least in TX. I have had to add CYA twice this spring and I probably need to add more today. The lake near us has gone up 12 feet in 3 months! Maybe lots of rain there too?

 

[robdac]

I haven't removed any water from the pool yet this year but I haven't had to add any for the last couple weeks either due to rain.

I've been adding "Pool Time" Chlorine Stabilizer from Home Depot. Cyanuric acid 100%. 15016 07:06 Z03 is printed on the bottom of the jug so I assume it was manufactured the 16th day of 2015. At this point I've gone through an entire 5 lb jug since 3/11.

Bacteria might be a possibility. We had the roof and pool deck pressure cleaned (water only) 15 March while I was attempting to also get the new SWG dialed in. I ended up removing a lot of sand from the pool and filter that was originally between the pool deck pavers. At one point I had the SWG up to 50% to maintain the FC at 5-6 while trying to get it dialed in. I didn't realize it was fighting something because it was brand new and the existing one was inop when me moved in. Now I'm running it at 17% with too much chlorine.

water is 86 degrees, 3300 ppm salt, 50 ppm borates, filter is clean

Test results from this morning:
FC 10.5
CC 0.5
TC 11.0
PH 7.6
TA 80
CYA 65
CH 375

 

[ewkearns]

I would have three questions, for sure....

1) How are you testing for CYA?

2) Noting this is a pool, at least, under cover..... how much water have you added, since 3/10?

3) What are the other numbers?

Folks with more experience may want to know how much direct sun (if any) the pool and/or spa receive. Did anything significant happen on or about 04/04? What kind of CYA are you adding?

I've been the victim of this issue, before.... and the potential cause is not pretty....

 

[robdac]

I would have three questions, for sure....

1) How are you testing for CYA?

2) Noting this is a pool, at least, under cover..... how much water have you added, since 3/10?

3) What are the other numbers?

Folks with more experience may want to know how much direct sun (if any) the pool and/or spa receive. Did anything significant happen on or about 04/04? What kind of CYA are you adding?

I've been the victim of this issue, before.... and the potential cause is not pretty....

1. Im using the TF-100 test kit and following the instructions as best as a "fairly" newbie can. When testing I also repeat the test several times to make sure what I'm seeing is accurate. I also note at what levels I can and can not see the black dot to arrive at my number. I really don't think this has been the problem but I still consider myself a newbie.

2. I'm not sure. I just add enough water weekly after doing my testing to bring it back to the proper level. I haven't had to add any water for the last two weeks however due to rain. I don't think I have a leak.

3. See the other numbers posted above as I filled out the info in the post.

What was your issue if I might ask?

The pool doesn't get a ton of direct sun. First, it's screened in. It has a large tree on the South side and the home shades it completely in the late afternoon.

Also of note is that I took the pool over 24 Feb after getting my TF-100 test kit and learning that the pool boy had the FC at 55 using liquid chlorine. That's not a typo. I replaced the inoperative SWCG and turned it on 11 Mar when the FC finally got back down to normal levels.

 

[robdac]

+1^ on something being up with dropping CYA numbers.

Then check whether you have something like an auto fill that is malfunctioning or are using techniques like vacuuming to waste, which would result in water replacement.

Adding: Water loss and replacement is my first guess and as noted above, your product may not be regular stabilizer. Using poolcalc, the first addition of 20 ounces should have taken you from CYA 60 to 74, but you only got an increase of 5 points.

I am the autofill.

I thought that was unusual too because poolcalc is usually dead on. I'm also pretty sure I'm using the correct volume for my pool in the calculator as I took the number off the engineering diagrams the previous home owners left.

I'm not vacuuming to waste and with the cartridge filter there's no water loss when I remove and clean it.

I haven't removed any significant amount of water from the pool since the end of the rains last (2014) summer.

 

[jtaves85mcss]

What are your daily Chlorine readings and volume of additions over a typical week during this period?

In my limited experience I would perform an overnight Free Chlorine Loss test. In the evening, after the sun is off the pool, test the FC, turn of your SWG, add bleach to bring it up to SLAM level, test FC again to confirm your start level, circulate the pool overnight. Then measure the FC early in the morning. You want to see a loss of 1 ppm or less.

I'm sure others may be able to better assist in pinpointing your issue and diagnosing the bacteria issue.

 

[robdac]

What are your daily Chlorine readings and volume of additions over a typical week during this period?

My FC readings are always 5 or more on the daily OTO test. I use a SWCG so I can't tell you how much chlorine is being added but recently I've had to back way off (from 50% to 17%) on the SWCG. Something was or is definately going on but I didn't realize it until now because I had just installed the SWCG and was getting it dialed in for the first time.

Yeah, it's weird. Since 10 March I have added a complete 5lb (by weight) container of stabilizer to the pool. Pool math says that equals a 42 ppm rise for my pool but I'm not seeing it. I can't figure out what's happening.

I'm going to run an OCLT tonight.

 

[mas985]

The rain might be hiding a leak. Is CH dropping as well over time? What about an auto overflow drain?

 

[robdac]

The rain might be hiding a leak. Is CH dropping as well over time? What about an auto overflow drain?

My CH numbers have jumped around likely due to poor (newbie) testing on my part.
3/10 475
3/19 325
3/25 325
every test thereafter has been 375.

There is no auto drain that I'm aware of. Last summer I had to drain water from the pool several times to keep it from overflowing.

I'm beginning to wonder if my initial CYA tests were somehow in error. Still, it would be hard for me to be off by 40.

 

[JasonLion]

What are the chances that you are adding something other than CYA when you think you are adding CYA?

 

[robdac]

What are the chances that you are adding something other than CYA when you think you are adding CYA?

Pretty close to zero. I can't speak to the quality of it however. It came from Home Depot and it appears that it was manufactured on the 16th day of 2015 based on the markings on the container.

I've been using this:
http://www.homedepot.com/p/Pool-Time-5-lb-Chlorine-Stabilizer-23216PTM/100045996

My numbers are so far off from what they should be given what I've added that I'm beginning to suspect user error on the initial few tests.

 

[JasonLion]

Definitely the correct stuff.

 

[robdac]

Definitely the correct stuff.

Which is a very kind way of saying it was probably the doofus performing the tests!

 

[AimeeH]

It's a test that takes some getting to know. Make sure you're consistant with holding the viewer about waist level on a sunny day with your back to the sun.

 

[tim5055]

It's a test that takes some getting to know. Make sure you're consistant with holding the viewer about waist level on a sunny day with your back to the sun.

hey, he's from Weston - an Arvida community...

Nothing there but sun, except for the scheduled afternoon showers.

My parents were in Weston - I was a Cooper City/Davie guy myself.