CYA Test results different

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mvoorn

mvoorn

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LifeTime Supporter
Aug 7, 2009
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Hi all,
I am having a hard time maintaining chlorine levels. We went on vacation for 3 weeks and left my neighbor teenage boy in charge. Specifically asked to use bleach, every other day add a gallon. If it rained, add more, etc... Unfortunately, we had a week of tremendous heat and a second week of rain all week (perfect storm for algae)! Pool got B.A.D, according to teenager. He shocked it, according to pool store instructions (Booooo... he didn't understand that we DON'T use pool chemicals)... anyway, he tried. Pool was close to OK when we got back, just a little cloudy, nothing major. I've been trying to get it back to normal but I am not able to maintain chlorine levels. Also, PH has been higher (8.2), so I added the Muriatic Acid. Dropped it to 8.4.
Now, since I've been back, I have been using my new FT100 test kit and the 3 times I tried, I got a VERY high CYA result (90+). I lost sight of the black dot almost immediately after adding the mix. However, when I take the water to Leslie's Pool, they always come back saying the CYA is fine (at 70). I asked them specifically to pay close attention to that CYA test and they checked twice (on the three different occasions that I went)... so I wonder what is going on with such different results... My questions are:
1. Is high CYA responsible for loss of chlorine?
2. Where is the CYA results most likely mistaken? My testing with FT100 or Pool store?
3. Does Muriatic Acid go bad after a while? Last year I purchase a 6-pack and I still had 4 gallons left, so that is the MA I used last week to get the PH lowered.
4. Anything else I might be missing to get this stable?
5. Can shocking (with bleach) bring the PH up high?
6. Oh, husband is wondering, does CYA evaporate with normal water evaporation? It has been so hot that we have probably lost about 1 foot of water (1/6 the size of our pool). I figured no, because the CYA wouldn't evaporate with the H2O... he thinks it might, so why is the CYA still so high (if it is), why hasn't it gone down at least a little.

Oh, last night I added a gallon of chlorine, this morning CC was 0, I shocked it (with Bleach) because I saw some yellow starting to form on the walls, added 4 gallons bringing the CC up to 27 this evening. Unfortunately it may have raised the PH (although I find it harder to read the PH at night, since it is hard to distinguish between different shades of bright pink with low light.

CC: 27
PH: 8.2
CYA: (FT100 results 90+)
TA:124
CH: Totally forgot to check for this one tonight.
Pool size: 13000 gallons/white plaster/ozonator with chlorine

THANKS IN ADVANCE FOR THE HELP!! I hadn't had any trouble for one year, and then I dared go on vacation!!! =D :blah:
 
I assume the CC (Combined Chlorine) number you listed above was actually FC (Free Chlorine)? Do you know what your CC level is?

The ph test is not valid above 10 ppm FC so don't adjust now.

DO NOT trust pool store cya measurements, they get this wrong more than right. Most likely your is close and it indicates you need to do a drain refill. Please explain the 90+ reading...was it 90 or not?
 
Yes, level posted was FC!!! Sorry!! CC was zero.
Since I ran 3 CYA tests with the FT100, the first test came to 100, one week ago. Then Pool store said it was fine (3 different times). Yesterday and today, I tested again for CYA, and two times I got 90.
THANKS!
 
mvoorn said:
Hi all,
1. Is high CYA responsible for loss of chlorine?
2. Where is the CYA results most likely mistaken? My testing with FT100 or Pool store?
3. Does Muriatic Acid go bad after a while? Last year I purchase a 6-pack and I still had 4 gallons left, so that is the MA I used last week to get the PH lowered.
4. Anything else I might be missing to get this stable?
5. Can shocking (with bleach) bring the PH up high?
6. Oh, husband is wondering, does CYA evaporate with normal water evaporation?
Click to expand...

1) no. High CYA is responsible for reducing chlorine's effectiveness. Thus, high CYA requires higher levels of FC to have the same sanitizing effect.
2) Trust your measurements: in broad daylight, keep your back to the sun, and hold the tube at waist level.
3) Should be fine.
4)
5)
6) Nope, only draining water will reduce it (excluding letting it go to swamp mode).
 
Well, 5 is not really a simple yes or no. Bleach/Liquid Chlorine is basic, so will raise the pH when you add it. However, when it gets used up, that is an acidic process, which brings the pH back to where it started. So it is a net neutral process. Also, when the FC is above 10 the pH test can read artificially high.
 
On #6, you don't lose anything but chlorine and water to evaporation. As it evaporates your CYA actually rises slightly but then goes back when you top off.

You can either SLAM now or lower your CYA and SLAM after that. It would be much easier to lower your CYA first, but it's your call. If you choose to SLAM now let your FC drop below 10 so you can get an accurate pH reading and get it lowered to 7.2 since you won't be able to test it during the SLAM.
 
Appreciate all the responses and help! I will test CYA in daylight with back against sun one more time (I've always tested inside the house). Most likely CYA is still high (maybe a little less high), but it seems like I will have to drain some of the water!
 
Since you have a good test kit and seem so surprised by your present CYA level I'm going to assume that it was much lower the last time you checked it (before vacation), so I would surmise that your current high level was most likely caused by whatever the pool store had the kid dump in the pool to shock it.
 
A couple of principles you can take away from this thread...

1. If you have a good test kit like the K-2006 or the TF-100, trust your own testing..ALWAYS

2. Nothing very good ever comes from stepping foot inside the pool store.
 

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Jeetyet said:
Since you have a good test kit and seem so surprised by your present CYA level I'm going to assume that it was much lower the last time you checked it (before vacation), so I would surmise that your current high level was most likely caused by whatever the pool store had the kid dump in the pool to shock it.
Click to expand...

YUP! CYA was 60 before I went on vacay! =(
 
duraleigh said:
A couple of principles you can take away from this thread...

1. If you have a good test kit like the K-2006 or the TF-100, trust your own testing..ALWAYS

2. Nothing very good ever comes from stepping foot inside the pool store.
Click to expand...

I couldn't agree more than statement #2 ! Since nobody really believes in the BBB method around me, it is really hard to let others take care of my pool if I go on vacation during the hottest months of the year (which is when constancy is needed to avoid a sprouting of algae!)! I don't know why I still doubt myself when testing with my TF-100... I never have problems (until I go on vacation, hahaha)! Imagine the amount of work and money I would save if I just stop vacationing and stay tied to my pool maintenance!!

So how do you guys do it when you leave home? How do you keep it from going bad?
 
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