What happened to my CYA and Chlorine??

[doncaruana]

I never really got my CYA all that high last year and we had so much junk floating in the pool when we opened this year, I didn't get it up to where I wanted it until a couple of weeks ago. Before that, and all last year, I had the intellichlor at 40% running about 8 hours a day. While last year I had no issues, the chlorine was a tad low so I just bumped it up to 10 hours and that seemed to get things back on track.

So, I got the CYA up to about 70-75 and I backed off the IC40 to 30%, still on 10 hours a day. I look down after a few days and the deep part is looking a tad cloudy. I check and I've got almost no chlorine and the CYA is down to 50. Taking the lazy route, I cranked the IC40 up for a few days and the water very quickly was back to being crystal clear. So, I figured maybe the CYA sucked up all the Chlorine and I needed extra to get back into balance, so I backed the IC40 back down to 40%. Whereas in the past that has been a good maintenance number, when I checked today, I have about 1.0 for Chlorine and what I'm guessing is less than 0.5 for CC (it was ever so slightly pink and went away with one drop).

My question is then why is that with no CYA, I ran perfect on 40%/8 hours last year, but this year with a full recommended dose of CYA and 40%/10 hours, I can barely keep ahead? What did I miss here and where did I lose a third of my CYA in the span of just a few days?

 

[JohnT]

The only way you could have lost CYA is through removing water and replacing it with new water.

 

[jblizzle]

Likely you are not getting enough FC because something took hold and is growing in your pool and consuming all the FC as fast as the SWG can make it.

To confirm, Perform the Overnight Chlorine Loss Test but likely you need to go through the Shocking Your Pool PROCESS

 

[doncaruana]

The only way you could have lost CYA is through removing water and replacing it with new water.

Well, there must be another way because that didn't happen. I did 2 separate readings at 70. The only thing that happened here is that we got a couple of inches of rain. But that shouldn't be enough to drop the CYA by 20.

but likely you need to go through the Shocking Your Pool PROCESS

The thing is, the water is crystal clear. It got ever-so-slightly cloudy and most people would have still called it clear. I need to get the FC level up before I can try the OCLT anyway, so I think I'll crank up the IC40 again first.


I also went back to pool school and noticed that it said " The higher your CYA level, the more FC you need to use to get the same effect." I guess I don't really understand exactly what that's supposed to mean. But it does seem that by upping the CYA, if my SWG was just keeping at "stasis" that the CYA would just sort of "suck up" the FC that the SWG was generating. Is that logical? So that, while raising CYA, I would need to increase the FC generation as well. In other words, I was "feeding" the CYA instead of the water. Or is that just wacky?

 

[jblizzle]

Turn the SWG off and boost the FC level up with bleach. Test the water at night. Run the pump all night. Test again before the sun comes up.

The CYA protects the FC from the sun. At the higher CYA level while you need a higher total FC level to maintain clear water, you are losing less to the sun so the daily addition is less. The higher CYA let the SWG not work as hard because less is lost to the sun.
You should find at higher CYA levels that you % setting can be lower to maintain the recommended FC levels.

 

[doncaruana]

Hey folks - I have a theory/question...

Cottonwoods were really bad here in SE Michigan. At one point, they made a blanket in my skimmer basket (like a lint blanket in the dryer) that I peeled off. They were thick enough that there was a suction vacuum when I pulled the basket out. Anyway, I haven't been able to clean the basket completely because the stupid things wrap all the way around. So I pulled the basket this morning and it was, in a word, nasty. The cottonwood actually looked a little green to me. So I'm wondering if my problem could be in not keeping the skimmer basket clean and allowing stuff to grow there. Does that sound feasible?

As an ancillary question - what the heck do you do to prevent that? Should I use a "skimmer sock"?

 

[sarahspins]

A sock can prevent the fibers from wrapping around the basket, but what you're describing with the fibers looking green definitely sounds like you have algae in your pool and need to shock.

 

[JohnT]

The only way you could have lost CYA is through removing water and replacing it with new water.

Well, there must be another way because that didn't happen. I did 2 separate readings at 70. The only thing that happened here is that we got a couple of inches of rain. But that shouldn't be enough to drop the CYA by 20.

No, there is no other way to drop CYA in less than a few months without replacing water except for RO filtering of the pool.

 

[doncaruana]

The only way you could have lost CYA is through removing water and replacing it with new water.

Well, there must be another way because that didn't happen. I did 2 separate readings at 70. The only thing that happened here is that we got a couple of inches of rain. But that shouldn't be enough to drop the CYA by 20.

No, there is no other way to drop CYA in less than a few months without replacing water except for RO filtering of the pool.

I can't imagine what would cause reverse osmosis (that is what you meant by RO, right?). I put 3 gallons of liquid CYA in my pool. The math and my tests showed it should be 70-75. Then we got a bunch of rain - literally over 2 inches in just a few days. The CYA is now down to 50. I didn't replace any water (my water level was actually high - I just waited for it to evaporate). The 2 inches of rain works out to about 600 gallons into a pool that holds just shy of 16,000. I don't know how it went down, but it went down.

On to more important issues...

I did the OCLT. I had 3ppm of FC last night (.5 CC) and this morning I had 2ppm FC (still at .5CC). So, according to the OCLT, since I only lost 1.0, the water is clean. All things being equal, would the CYA level affect this test at all? I mean, does it sound safe to trust it?

On a side note, my pH is a tad high (7.8 or so - hate "interpreting" those Darn colors). I think that's hurting me as well - in goes the acid this morning.

 

[duraleigh]

Well, there must be another way because that didn't happen.

I can't answer where the CYA went but I can assure you there is no other way. I would chalk it up to one of those mysteries and not dwell on it.

 

[doncaruana]

Well, there must be another way because that didn't happen.

I can't answer where the CYA went but I can assure you there is no other way. I would chalk it up to one of those mysteries and not dwell on it.

I'm over it

 

[mk1]

I thought I read somewhere on here that CYA can get converted to ammonia? And be a big FC eater then?

 

[jv92red]

Probably over in the deep end section of the forum. I believe someone wanted to add ammonia to decrease the CYA but the ammonia would just be converted by the FC. Check this out:

http://www.troublefreepool.com/degradation-of-cyanuric-acid-cya-t8880.html

 

[jblizzle]

The conversion can happen, but is it usually in closed pools over the winter. Also, I prefer the OCLT to be done with FC closer to shock level. With your low levels, 1ppm was 33% which is a lot.

 

[spidey07]

Agreed. Sounds something is trying to take hold also evidenced by cloudy water and swg unable to keep up.

Raise to shock level with bleach and do oclt. Swg off. When you let FC get below min you're inviting algae. That's why it's the absolute minimum.

It's a common thread. My swg can't keep up but pool looks fine. That's because your just barely able to keep it in check but it's not eradicated.

 

[doncaruana]

It was sunny yesterday and I had the day planned with my dad (no time to manage pool) so I cranked the IC40 up to 90% and let it run all day. 10 hours of pump time and the IC40 should have produced about 8 ounces of pure chlorine, which, if I've done the math right, is around 4ppm. And I started off at 2 in the morning. 2 hours of 3 kids swimming (from 7 to 9pm) and this morning, I'm back at 2. So...I think I'm barely staying ahead of whatever it is, although the water looks pretty clear (ever so slight cloudiness MAYBE in the deep part).

So...guess we need to shock...

A few questions first though...

My pH is right at 7.6 now. Should I bring it down to 7.4 before shocking?
Since my CYA is only at 50, can I extrapolate the chart and figure my shock level to be around 18-20 or so?
Since I'm not quite in "dire" need just yet anyway (ie pool isn't green or really cloudy or anything), do I need to go that high (assuming yes, to be safe anyway)?
Also, at what FC level can we swim again?
And, more importantly, any ideas on how long it might take to bring down the level to useable again?
Lastly, should I turn off the SWG until the levels come back down close to the target range?

 

[jblizzle]

Lower the pH down top 7.2 or so. The shock levels are the same for all pools, so just use the non-swg table. You need to maintain that level until you pass the 3 criteria to stop. It is safe to swim when the FC is below shock level and it will drop quickly once the process is complete.