CYA mystery

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blazin

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Jul 29, 2017
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Franklin, MA
I had a thread in my build going last season and assumed this was newbie error. This season I'm convinced something else is occurring.

Cya levels middle of May was 35 after adding ~128 oz of dry stabilizer.

This was up from 0 after pool opening.

Added another 3-4 lbs plus a few tabs after I had to replace water due to a waterline tile fix. That was a month ago.

I've felt like I've been fighting chlorine loss pretty rapidly.. testing was yielding sub 20, aka 0.

I was down to the end of my tftkit cya test. Ordered more tested today... 0.

I just added another 0.5-1 lbs which is no where near enough to raise it in my pool, but my bigger concern is where is the cya going?

I thought that could only go down by draining. I didn't drain 16k gallons in June, but I surely added enough to push me closer to 50ppm,based on a 20-30 ppm reading.

Is there another way to kill cya?? Mask it?? Something??

I know tabs are known to raise this, but at this point it may be worth it if my pool mysteriously ingests cya. Thoughts?
 
Post a complete set of test results. Ammonia will eat CYA. If you have 0 CYA, 0 FC, and low pH you likely have an ammonia problem.

Stop putting in tabs or stabilizer until you get this figured out.
 
CYA is consumed by a bacteria that results in ammonia build up in the water. Not likely if your pool holds any amount of FC
CYA very slowly degrades at elevated water temperatures. Yours is reducing more than a little.
A leak will reduce the CYA level. You should recognize a leak large enough to cause what your seeing.
Or the CYA you are using is not raising your level to begin with. Have you used the same brand all the time?
 
Ok ill run an ammonia test and report back. FC read 0.5 this morning. Been difficult to keep up.

If FC is low or zero for a few days could this kill the cya?

I've been adding 1/2 gallon 12.5% every 2-3 days to keep up with the loss. But it definitely stretched to a week mid June. Trying to maintain 2 ppm minimum.

Again, let me test and I'll get back.
 
You are not adding near enough chlorine to your pool, and near as often as you need to.

I too now suspect ammonia.
 
mknauss said:
You are not adding near enough chlorine to your pool, and near as often as you need to.

I too now suspect ammonia.
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Really? Pool math says 3.7 ppm raise from 1/2 gallon, Target is 2 -5 ppm. That's nearly 15/week, loss should be 1-2 ppm /day. Net should be positive. Does 1-2 ppm loss assume 30ppm cya?

What's the ammonia cure before I go out and get test strips?
 
blazin said:
If FC is low or zero for a few days could this kill the cya?
Click to expand...

It would be the ammonia killing the FC and CYA. Ammonia feeds on CYA and it increases.

For every 1 ppm of ammonia you have it will take 10 ppm of CL to kill it.

Fish pet stores have ammonia tests.

This a thread on a difficult pool ammonia problem - Help!!! Yikes!
 

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Add 10 ppm of liquid chlorine and test your FC in 30 minutes.
 
Target 10ppm of FC and retest FC and CC in 15 minutes. Report back.

Fyi, a normal daily FC loss is 2-4ppm. And with lower CYA it could be higher depending on sun exposure
 
jblizzle said:
Target 10ppm of FC and retest FC and CC in 15 minutes. Report back.

Fyi, a normal daily FC loss is 2-4ppm. And with lower CYA it could be higher depending on sun exposure
Click to expand...
Ok.. will do. I was searching and found 1-2 loss/day. If it's really as high as 4, that means 1/2 gallon a day is more reasonable with a full gallon at the end of the sunscreen and adolescent urine filled weekends.

Thanks all be back in 15
 
Lynnster52 said:
Blazin - did u raise FC to 10 and it dropped to 4.5 in 15 mins? I'm doing to 10 ppm now & will report my results in 15 mins. I had hoped you did same so just wondering if you misunderstood or is it me? lol Good luck to both of us! (we got slammed with 3 thunderstorms today...another coming later. Pool got extra filled up! Can't win!)
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Raised to 10ppm by pool math, it lowered to 4.5 in about 15 mins. But my CC was 0 added more in to raise to about 8.2 by pool math. Checking in about 30 from now
 
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Lynnster52 said:
Good luck...that's what I thought you'd done. I was good after 15 mins. FC at 10 ppm. Are you positive you have just 16,700 gal pool? I realize it's free-form but my pool is almost same size (19x37 with a deep end) & ours is 27,500. I wonder if you have more water volume, which might explain something, but I leave that to the experts! ;)
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Just tested at 7.5 FC with 0.5 cc I decide to test early due to the rain any second.

I had low ammonia 0.5 ppm on a test, and it ate 5ppm in 15 mins. Sounds like that was my issue I'll treat this like a slam and check in the morning for the overnight loss.

My pool has a sunshelf and only goes to 6 ft depth. Normally pool math is dead on at 17k gallons. So I think it's right
 
blazin said:
Raised to 10ppm by pool math, it lowered to 4.5 in about 15 mins. But my CC was 0 added more in to raise to about 8.2 by pool math. Checking in about 30 from now
Click to expand...

Ammonia does not create CCs.

Keep raising to 10 ppm after each 15 minute check.
 

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