PH drop. CYA is 0. I think I messed up :)

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nikon5400

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Jul 20, 2013
299
Northeast
My pool is still covered. About a week ago I tested the water, PH was 7.6-7.7. Now PH is 7.2 at best. I added maybe 1ft of water (don't remmeber if pool water was added before or after I did the test) and had pump running for a few hours. No chemicals were added. Alkalinity hasn't changed much, now it's 110-120


I never had PH drop before, it always rises. Any idea what can be the reason? I'm planning on opening pool today, but I can see the water is pretty bad, I see some brownish foam in the skimmer. I did very bad job last closing - didn't add algaecide and didn't shock (had issues with algaecide turning into ammonia previously. had 0 issues with pool last year, so decided not to shock and closed with FC level around 7.5, but it went to 4-5 in 5 days while was covered)
Thanks


EDIT Removed the cover, added chlorine to bring to shock level. Tested in about an hour, less than 1. Tested CYA and sure enough it went down from 30 to nothing. I tested it last week and it was 30. I didn't retest it today, because I assumed it's still 30.... In less than a week from 30 to nothing while the pool was still covered. Why would it happen?

I bought stabilizer and already have socks in skimmers and on return.

Question - With CYA 0 what kills chlorine more, the sun or the algae? Should I be adding chlorine now or should I wait until dusk? (don't want to waste another ~~$15 if sun is killing it right away)

Thanks
 
Re: PH drop

Good morning Nikon. Before we get too far ahead of ourselves, can you please post for everyone what test kit was used to obtain those results? Also provide your pool specific data, much like what you see in my signature, so that others can help give you a good course of action? The fact that you mentioned using an algaecide in the past gives us the impression you may be following the advice of a pool store - something you'll find unnecessary if you follow the TFP methods. Thx!
 
Re: PH drop

I used to close with higher chlorine level, but then I was told the solid pool cover may deteriorate faster with higher levels of chlorine, so I decided to go easy on chlorine and tried the algaecide (method was was mentioned in the closing instructions). I believe this was the only time I used algaecide and I wasn't happy with the results, so I didn't use it last fall. The only thing I didn't do last fall - I didn't shock the pool before closing, but I had 0 issues with the pool water last season, so I decided no to shock and closed quickly.

The other levels are OK.
CH 180 ( a little low)
CYA 30. EDIT - I was wrong. I didn't retest CYA assuming reading of 30 from last week is still accurate. I was wrong.



I don't know if I should raise PH to 7.4-7.6 before I shock or if I should shock first. I believe chlorine is more effective with lower PH readings.

I use TF100
 
Re: PH drop

I would leave the pH at 7.2 and begin the SLAM Process. pH tends to rise slightly during a SLAM so you will have some breathing room to guard against it increasing too much. And, yes, chlorine is slightly more effective at lower pH levels. Important point...do not try to adjust pH during a SLAM - don't even test it until the SLAM is done and FC drops below 10 ppm.

As far as the SLAM goes, the most important part is the M for Maintain, as in continually maintaining the FC as close as you can to the recommended target SLAM ("shock") level according to your pool's CYA which is defined here: Chlorine CYA Chart. Note that the target is just that - a target - not an absolute minimum. Don't sweat it if FC is within a point or two either side of this target.
 
nikon5400 said:
Tested CYA and sure enough it went down from 30 to nothing. I tested it last week and it was 30... In less than a week from 30 to nothing while the pool was still covered. Why would it happen?
Click to expand...

nikon5400 said:
Removed the cover, added chlorine to bring to shock level. Tested in about an hour, less than 1.
Click to expand...

It's possible that the CYA was converted into ammonia. That plus the fact that your chlorine is not holding as witnessed from it going from shock level to 1 in about an hour is another sign that this has happened. It takes anywhere from 9 to 20 ppm of chlorine to deal with 1 ppm of ammonia. Add chlorine at SLAM Process (shock) level and retest at 30-60 minute intervals. Repeat until you have an FC level at, or greater than, 5 ppm and a CC of 0.5 or less. It may take a while. Once your pool begins holding chlorine, then add CYA and get it up to at least 30 ppm.

nikon5400 said:
Question - With CYA 0 what kills chlorine more, the sun or the algae?
Click to expand...
Ammonia will consume chlorine at a considerably higher rate than either the sun or algae.
 
BoDarville said:
.... It takes anywhere from 9 to 20 ppm of chlorine to deal with 1 ppm of ammonia. Add chlorine at SLAM Process (shock) level and retest at 30-60 minute intervals. Repeat until you have an FC level at, or greater than, 5 ppm and a CC of 0.5 or less. It may take a while. Once your pool begins holding chlorine, then add CYA and get it up to at least 30 ppm.
Click to expand...

how important is it to add CYA only after I have FC at or above 5?
I added CYA soon after chlorine dropped to zero and been adding chlorine after that.
also if your cya is 0 what is the shock level?

Thanks
 
nikon5400 said:
how important is it to add CYA only after I have FC at or above 5?
Click to expand...
What causes the ammonia problem is bacteria that consume CYA and convert it to ammonia. You want to make sure the ammonia and the bacteria that cause it are neutralized by the chlorine before you add CYA. Otherwise, the bacteria will feast on the CYA and cause more ammonia. Allowing the chlorine to work with no CYA in the water will accelerate the ammonia conversion process as quickly as possible.

nikon5400 said:
also if your cya is 0 what is the shock level?
Click to expand...
Per Pool Math, the shock FC level is 10 ppm.
 
BoDarville said:
What causes the ammonia problem is bacteria that consume CYA and convert it to ammonia. You want to make sure the ammonia and the bacteria that cause it are neutralized by the chlorine before you add CYA. Otherwise, the bacteria will feast on the CYA and cause more ammonia. Allowing the chlorine to work with no CYA in the water will accelerate the ammonia conversion process as quickly as possible.

Per Pool Math, the shock FC level is 10 ppm.
Click to expand...

I'm still loosing chlorine. Just went from 11 to 9.5 in about an hour.
Should I remove stabilizer (socks) for now? I'd say half of it is dissolved already, but I can remove it if that's what you recommend.

On a side note - CH reading was 180 and now with PH of 7.2 I was at CSI -0.48. However, I retested everything just now and CH is UP, around 210-220, TA is UP a bit too 120-130 (was 110 last week)

Question - can the chemicals I have in the water now (stabilizer and Chlorine up to 12) affect CH and TA reading?

Another question - if I decide to add calcium, can I add it while stabilizer socks are in the water and FC at the shock level?

My current levels
Chlorine 12 (bringing it up to 12)
PH 7.2-7.3 (was 7.6-7.8 a week ago)
CYA 0 (socks in the water) (was 30 a week ago)
TA 120-130 (was 110)
CH 210-220 (was 180, maybe a bit higher)
Plaster pool, 23k gallons.

It seems like everything was fine last week (except for a little low CH), but something turned my CYA into ammonia within the last few days. I didn't add anything other than water to the pool. How do I prevent this from happening in the future? I had similar issue last year and I blamed algaecide for that, but now I see algaecide may not have been the issue (didn't use it in 2014).

Should I be opening pool earlier, when it's a bit colder?

Thanks.
 

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I would leave the CYA sock in the pool. Don't adjust CH or TA while SLAMing, wait until you are finished and everything has settled down. Just focus on the SLAM right now.
 
If you're only losing 1 ppm of FC overnight, then your chlorine is most definitely holding. You can keep the CYA sock in the pool. I would keep the SLAM going until CC drops to 0.5ppm or less. Although the newly added CYA may take up to a week to register on a test, dose FC as though all the CYA you recently added is dissolved into the pool. Keep the filter running to help clear the water.

nikon5400 said:
How do I prevent this from happening in the future?
Click to expand...
There are no guarantees, but following the recommended closing procedures outline in Pool School will reduce the odds of a recurrence. Also, it's best to avoid closing your pool until the water temperature drops below 50°F.

nikon5400 said:
Should I be opening pool earlier, when it's a bit colder?
Click to expand...
Yes, that will help. I would open once the water reaches 50°F.
 
I'm still curious why CYA dropped from 30 to 0 in 6 days when the pool had cover on. PH dropped from 7.6-7.7 to ~7.2.

I wonder if I there was something in my pump or filter. I cleaned the filter cartridges before closing.

Also, this is 2nd opening in the row I'm having this issue with CYA and I never had it before (although last time it wasn't 0, but more like 10-20). The only thing I did differently the last two closings - I put the cover on with slightly lower chlorine level. But then again, why did the CYA drop within the last 6 days before opening.
The only thing I dd in those 6 days - I lifted the pool cover from the steps to get the water sample, remove the plugs etc. That section of the pool didn't have the cover on for a few hours only
 
The conditions that lead to bacteria converting CYA to ammonia are not fully understood. What we do know is that it can occur when FC drops to zero and is usually most common upon opening the pool for the season. We definitely see a seasonal trend with this. The later you can close your pool and the earlier you can open it will lessen the likelihood of occurrence.

I can tell you that the CYA test is subjective and sensitive. Make sure that you are doing the CYA test accurately (scroll down to the CYA section -Post #8):
Extended Test Kit Directions
 
I started seeing bottom drain yesterday, don't see any algae, but the water today is just as cloudy as it was yesterday. Overnight loss about 1.5PPM CC 0.

Keeping FC at 12.

What should clear it up, chlorine or the filter? I don't think my 10yr old cartridges are going to do much, but should I clean the cartridges now? No visible algae, no derbies, just a couple worms in the water and maybe some dust settled on the floor. (I see dust on the steps when I brush). My cartridges do not capture dust, I need to get a pool vac with it's own filter

Will raising FC above the shock level speed up the process or is it just a waste of money (temp is in 80s, with sun hitting pool most of the day)

PH 74.7.6 (up)
TA 90 (down)
CH ~~230 (up)
CYA 25-30 (registered in less than 60 hours. (just tested it for the first time). That's much quicker than I thought it would take. I had 4 socks and I believe the last one emptied yesterday.)
water temp now 72 (up from ~65 when opened. I believe it was ~75 last night)

we had some rain yesterday, maybe that's what affecting TA?
 
Your CYA could still go up some. Make sure to test when it has been a week since you added it just to make sure.

Chlorine AND filter will clear your water. You are on the home stretch. Do NOT give up now! This is the hardest part because you do not really see big changes so start to question if you will ever get done.

Rain should not do much to the water. It can causes changes but not big one.

Kim
 

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