CYA

[lucasaltic]

Ok so I’m going to commit TFP heresy and ask a question that I’m sure I’ll get torn to shreds over, but I’m going to ask it anyway… if you have an over-sized SWCG, why do you need CYA? I know all the science behind it, but if you’re continuously producing chlorine and you’re running it during the day, and you can maintain sufficient levels, what’s the problem with going without it?

The main reason I ask is that I’m constantly adding it in the summer months due to high water exchange from daily afternoon Florida rains. If I’m okay with using the extra power and wear and tear on the cell, is there any other reason to use CYA?

[Looks up from the podium at the angry mob.] Are those stones I see?

Luc

 

[mknauss]

Don't use it.
Crank up the SWCG to be sure you keep 3 ppm plus in the pool water. Be ready for some very uncomfortable water, dry skin, irritated, eyes, hair issues (for those with hair!), faded swimclothes --- etc.
Also order a back up SWCG cell. Yours will be used up pretty quickly.

The half life of FC in an outdoor pool without CYA is 50 minutes -----

 

[Donldson]

Seems a better idea if you constantly have to add CYA would be to add a tablet feeder after the SWG and fill that as needed to maintain a good CYA level. Then you'd dial back the SWG and the cell will last longer, instead of having to dial it WAY up and replacing the cell much sooner.

Out of curiosity, if you're constantly having to add CYA in the summer due to rain aren't you also having to add salt just as often?

 

[Jimrahbe]

Lucas,

Why are you the only person in Florida that can't keep CYA in his pool???

We have chemical "recommendations" that we find work best for most members. We lack the funds to come over to your house and force you to use CYA, so feel free to ignore our recommendations and run your pool any way you want. I have requested additional funds for riot gear, an armored vehicle, and tear gas, but so far, my requests have been denied.

I do suggest that it would be better for you to have at least 20 or 30 ppm of CYA as it will make the chlorine less harsh.

Thanks,

Jim R.

 

[Steve-D]

Who would have thunk it...a valid argument for the regular use of Chlorine tabs!
<waits nervously for the thunder-clap>

 

[Donldson]

Who would have thunk it...a valid argument for the regular use of Chlorine tabs!
<waits nervously for the thunder-clap>

Shh, don't tell anyone but I haven't added pure CYA to my pool in many years. Every CYA molecule that's been added has been a byproduct of a chlorinated isocyanuarate.

 

[mgtfp]

Have a look at chem geek's version of the FC/CYA chart, as it also contains a row for CYA=0:

Chlorine/CYA Chart

EDIT: You will find a simplified and standardized version of this chart at Pool School, Chlorine / CYA Chart. Chlorine/CYA Chart by Chemgeek FC = Free Chlorine in parts-per-million (ppm) CYA = Cyanuric Acid in parts-per-million (ppm) CYA ........... Min FC3 ..... Target FC ...... Yel/Mstrd...

www.troublefreepool.com

You will notice that the target FC for SWGs with no CYA is about 0.07ppm (target FC with SWG is about the same as min FC w/o SWG). SLAM-FC with no CYA is 0.64ppm.

Without a professional testing and dosing system, it is pretty much impossible to maintain these low levels, especially with a "slow" source of chlorine like an SWG, without risking to slip too low with varying UV- and bather loads, or when a child pees into the pool. Once you have a few cloudy days with no bather load, your FC will sky rocket.

You will have to maintain higher FC levels (way higher than SLAM equivalent) to have enough buffer. By industry standards these higher levels of up to 4, 5 or even 10ppm (with no CYA, these levels are insane, with CYA they would be completely acceptable depending on the exact CYA level - it's all relative) are what you often find in public pools. Not much fun to swim in. All the effects listed by Marty are the consequence.

Up to you.

 

[lucasaltic]

WELL, I survived! Whew!

In all seriousness, thanks for the comments. All valid things I hadn't completely considered. Sounds like the bottom CL range for 0 CYA is too low to achieve a stable chlorine level very close to zero. @mgtfp thank you for that clear insight.

To answer a few questions above:
@Donldson: Re salt makeup, I believe my salt levels may have been off the charts high. I had been going by the SWCG reading which always showed around 3,000 ppm (and occasional use of completely USELESS salt strips) until I found this wonderful forum. Once I tested it with reagents (about 3 months after acquiring the pool), salt was coming in around 4,500 ppm but my CYA was zero (test strips showed it in the correct range). I had added CYA in April at the same time I added salt. So salt must have been really high then. I also did have a skimmer leak which required a lot of water makeup until I tracked it down. Short answer to the question is, yes I very likely would have had to add salt in addition to CYA, but salt was probably already too high. How I ended up with zero CYA and still relatively high salt, I'm really not sure.

@Jimrahbe: I don't know! It keeps dropping. I added 6 lb to a 9,900 gal pool. That should have given me about 72 ppm but a week later I'm at 50. Maybe I still have a pool leak and it's getting masked by the recent rain? Currently, I do have about 50 ppm CYA.

Thanks to you all for the diligent insight.

 

[Kjac081]

I’d verify you don’t have any more leaks. I went through this over the past year; Pool builder finally regrouted the skimmer box and several loose spillway tiles. Do the bucket test to confirm no leaks(search here on how to do the bucket test). Drive me crazy trying to balance water, and that’s one way I knew me wet yard was a pool leak vs irrigation pipe.

What I do to help maintain balance in the rain season is drip water level about 1/2” below the overflow, and use a overflow drain block off plate. It takes seconds to install or remove, and prevents a lot of overflow from splashing and light rains. I’ll remove it when there is a tropical storm and the water gets to the coping

 

[lucasaltic]

Cool. Thanks for the advice. I don’t think I have an overflow. If my pool tops out, it’s going to be on to the deck.

Incidentally, I did watch the last downpour and noticed I have a gutter outlet near the pool that will actually shoot water over the deck and into the pool if the rain gets strong enough. Only happens for a couple of minutes which is why I probably never notice it. So that could be why I’m taking in more water than others in my region.