Another CYA Question

[JIMNSC]

S'me again, Margaret...... I would like to report that I have eliminated chlorine block using Ultra bleach and the BBB method. Now, my CYA is still sky high and I understand no chemicals will lower it.

Here's my question: Will it lower over time on it's own?

I looked for this for a long while and never saw a reference to it before I posed the question. I'm just thinking that it will lower over time provided the other chemicals are correct. I may be wrong and probably am. I have been lowering my pool about 8 inches at a time and re-filling with tap water to no avail. I won't even attempt to drain the pool on my on due to the problems I may cause with the vinyl liner. Bad news is no local pool companies around here want to do it either.

Now you know why I posed my question.

Thanks for any help - Jim :?:

 

[chem geek]

Jim,

Unfortunately, CYA is very stable and will not breakdown over time under normal conditions in a pool (it might breakdown very, very slowly over an entire season, but not by much). It does get consumed by soil bacteria so some people find that over a winter, especially if they don't maintain chlorine, that the CYA level drops, but they often have a green swamp for a pool. Also, when the bacteria consume CYA they produce ammonia and it takes a lot of chlorine to get rid of that ammonia.

So the only real option is to do partial drain and refill as you have been doing. Yes, it will take a long time. Using somewhat continuous dilution which is what you are mostly doing, even replacing the entire pool water volume over time only results in getting the CYA lowered to 37% of its original value.

Just measure your CYA level (I assume you have a good test kit such as the one found at tftestkits.com or a Taylor K-2006 test kit) and maintain a high enough chlorine level for that CYA level -- generally an absolute minimum FC level of 1/14th the CYA level (i.e. a CYA/FC ratio of 14) and making sure you add enough chlorine so that you don't go below that minimum by the time you next add chlorine. A target FC level of 1/9th the CYA level (i.e. CYA/FC ratio of 9) is a more typical target for more safety.

There is one other option, but more expensive, and that is to use a weekly maintenance dose (after an initial startup dose) of PolyQuat 60 algaecide. You will be able to have a lower FC level with the high CYA level if you do that, but should still try and maintain around 3 ppm FC or so. This is not the normal recommendation, but it is another (albeit expensive) option. Bacteria are far easier to kill than algae so your pool will still be safe, but the algae will be kept away by the algaecide and not by the chlorine alone. At least this is something you can do until your CYA levels get down to the point (30-40 ppm) where you can just use chlorine alone at normal levels around 3-4 ppm FC.

Richard

 

[Rangeball]

What you are doing, draining and refilling (and making certain to stop all use of CYA products) is the only way to lower CYA. If it's sky high, it takes time.

You can drain to the point of leaving about 1' of water in the shallowest end of your pool safely, assuming you don't have a high water table. You can also add water as you drain.

Only way to do it. Sorry.

Ps- You can leave it high, close your pool without taking steps to kill/prevent algae and it may be gone by your next start up as algae can consume it, but that's no fun.

 

[JIMNSC]

Thanks, Rangeball. In my particular pool that would mean draining 44% of the water. In your opinion, would that much fresh water added back reduce the CYA significantly so it would be worth the effort? I do appreciate your response.

Jim

 

[Rangeball]

Jim, it depends on what the "sky high" CYA number is. My dad's AG pool is over 100 ppm. He doesn't want to drain, so I just have him maintaining FC at 15 ppm, per the chart.

If I were you, unless the CYA were causing me major problems, I'd live with it at a proper ppm of FC per the chart, and let it drop over time due to splash out, vacuum to waste, close/open, etc.

That's what I did when the pool store had mine so out of whack. It's about 25 ppm, and I won't let it get any lower.

Oh yeah, I think Richard posted while we did. Make sure you read what he writes. Everytime you see his name

 

[JIMNSC]

Hey Richard - didn't even see your post before getting an email advising of Rangeball's. Thanks for your information also (sure would be nice to own some of your knowledge)! You both have given me things to weigh. Having had tremendously good luck with my pool for the last 5 years, I didn't have a pressing need to become real knowledgeable on pool chemicals. Boy, at the reading I've done the past two weeks though. Thanks again for taking your time to help me. Your input is invaluable to me.

Jim

 

[JIMNSC]

Jim, it depends on what the "sky high" CYA number is. My dad's AG pool is over 100 ppm. He doesn't want to drain, so I just have him maintaining FC at 15 ppm, per the chart.

If I were you, unless the CYA were causing me major problems, I'd live with it at a proper ppm of FC per the chart, and let it drop over time due to splash out, vacuum to waste, close/open, etc.

That's what I did when the pool store had mine so out of whack. It's about 25 ppm, and I won't let it get any lower.

Oh yeah, I think Richard posted while we did. Make sure you read what he writes. Everytime you see his name

Two quick questions from your post: 1) What chart; 2) is it safe to swim in 15ppm FC? I promise not to be a gigantic pest.

By the way, my CYA is 130.

 

[ktdave]

Jim,
The chart Rangeball refers to is "ben's best guess chart" from poolsolutions.com (below).

Stabilizer . . . . . . Min. FC . . . . Max FC . . . 'Shock' FC
0 ppm . . . . ... . . 1 ppm . . . . . 3 ppm . . . . 10 ppm
10 - 20 ppm . .. . . 2 ppm . . . . . 5 ppm . . . . 12 ppm
30 - 50 ppm . .. . . 3 ppm . . . . . 6 ppm . . . . 15 ppm
60 - 90 ppm . . .. . 5 ppm . . . . . 10 ppm . . .. 20 ppm
100 - 200 ppm ... . 8 ppm . . . . . 15 ppm . . .. 25 ppm

As far as the safety of swimming in 15 ppm FC water is often debated here, but I believe the majority believe it to be safe.

 

[Rangeball]

Jim, the common thinking is that CYA protects chlorine by binding to it, making the chlorine less useable, or strong if you will, than unbound unstabilized chlorine.

Looking at that chart, compare no stabilizer to 100-200ppm stabilizer. No stabilizer recommends 3 ppm. 100-200 recommends 15 ppm.

In this scenario, the 3 and 15 have the same killing power, so even though the 15 is higher and pool stores will swear you're gonna melt, for all practical purposes they provide the same sanitizing strength.

Swim away

Oh, and your welcome. All I know (just a drop in the bucket) I learned from places like this. If I can pass something along when I'm able, I'm happy to do so

 

[JIMNSC]

See you later guys - I'm going swimming!! All this time I wouldn't allow swimming if FC was above 3ppm.

You all have been a big help - and not unlike Clint Eastwood - you have gone ahead and made my day. Hope I can help you all in the future.

Jim

 

[Rangeball]

By the way, I highly recommend Dave's test kit. If you choose to let CYA drop over time through displacement you'll need to be able to accurately monitor for higher free and total chlorine levels, which sticks, OTO and DPD kits won't do (well, you can use the shotglass method of dilution with either, which will get you in the ball park).

If you don't have a good feel for your CYA level and you have a Walmart near you, see if they sell the HTH 6 way drop kit. It has a stabilizer test, so you can at least try to match your pool up with the chart.

Good luck

 

[chem geek]

Have fun swimming! For your info, the following all have the same amount of disinfecting chlorine and are roughly at the mid-point between Ben's "Min" and "Max" columns in his chart and represent 0.05 ppm of disinfecting chlorine (hypochlorous acid):

15.0 ppm FC with 130 ppm CYA
11.5 ppm FC with 100 ppm CYA
9.2 ppm FC with 80 ppm CYA
7.0 ppm FC with 60 ppm CYA
5.8 ppm FC with 50 ppm CYA
4.7 ppm FC with 40 ppm CYA
3.5 ppm FC with 30 ppm CYA
2.4 ppm FC with 20 ppm CYA
1.2 ppm FC with 10 ppm CYA
0.1 ppm FC with 0 ppm CYA

You can see the general rule that you get the same disinfecting chlorine level (of 0.05) when the CYA to FC ratio is around 8.6 or so. This chart shows the FC level required to achieve the disinfecting chlorine level indicated in the column at various CYA levels indicated in the rows. Ben's "Min" values in his chart roughly correspond to the "0.03" column while his "Max" values roughly correspond to the "0.07" column. His "Shock" values don't correspond well, but are somewhat like the "0.30" column. His chart also takes into account the fact that no one can realistically maintain 0.1 ppm FC in their pool, even with no CYA. It gets used up too fast.

Since the concentration of disinfecting chlorine determines the reaction rate for oxidiation and killing algae and pathogens, your swimsuits and skin should have no problem in the water with the 15 ppm FC in 130 ppm CYA. However, when you get out of the water, then realize that the 15 ppm FC is a larger total capacity of chlorine so though it reacts slowly it will be able to react with more swimsuit material over time than a lower level of FC. So rinsing off after leaving the pool would help, though it's really not a huge problem. The same principle applies to drinking the pool water since the issue there is not with the reaction rate (which is fast due to nitrogen-bearing organics and reduction agents in saliva), but with the total amount of chlorine. So don't drink the pool water (but you already knew that :lol: ).

Richard

 

[mas985]

Richard,

Is this formula still correct:

(FC as ppm Cl2) = ( 2.7*(ppm CYA) + 6 ) / ( 6.6 + 1/(ppm HOCl) )

I found it on one of your postings but is seems to be a bit off from the numbers you posted.

[EDIT] Never mind, I just realized that was for a PH of 7.5 and you mentioned in the post it was only approximate.

 

[LadywithIron]

Jim,

What kind of gallons are we talking with your pool, and what kind of an incline from shallow to deep?

What you need is some kind of vessel that is lightweight enough to put into the pool after draining that 44 percent, that you could then fill with fresh water at the same rate that you would drain the over stabilized water. This would keep your water level the same on your liner to prevent dry out, and then, once the vessel/container was full, you could stop draining, and empty the fresh unstabilized water into the pool, then fill the remaining 44 percent with fresh water also. But you need something that will hold enough water to make a difference.

The plastic septic tanks come to mind, they hold a lot of water, or maybe even just a blow up donut ring pool would work if you plugged the holes very well. The fire department might have something along these lines......

Don't feel too badly, after 8 years of running above ground pools, I just HAD to use the fastest faucet on the place and ended up with a pool full of IRON WATER.

 

[JIMNSC]

Lady with Iron - I have 13,230 gallons and for the life of me I can't picture how to do what you suggest.

 

[duraleigh]

Lady with Iron - I have 13,230 gallons and for the life of me I can't picture how to do what you suggest.

Jim,

What she's talking about is a way to drain off your CYA water and replace with fresh while maintaining the pool water level at the same spot. Generally, draining a pool, is not a great idea and has to be done with caution.

She's suggesting floating a big tank in your pool and starting to fill it with fresh water. Then, as it sinks, you drain off an equal amount of pool water so the overall level of the pool doesn't change. Once the tank is full, you release the tank water into the pool and, done often enough, you can completely change out your pool water without ever having drained the pool. That strikes me as a monumental task.

Another method that is frequently mentioned (although, I have never seen a post of anyone actually doing it....kinda makes you wonder) is to obtain a plastic sheet large enough to cover your pool and the pool walls. The sheet acts a divider so as you drain off the original water underneath the sheet, you refill fresh water onto the top of the sheet and, again, the water level never changes but you have changed out your pool water. Again, that's nice to post up but I've never heard of anyone actually doing it.

Practically, it makes sense to me to drain 1/2 your water and refill with fresh. That'll cut your CYA by half. If that's not adequate, drain 1/2 your water again and refill.....that'll reduce your CYA by half again and should get you in a manageable condition.

Even more practical to me is to simply deal with what you've got (by keeping your Cl level up there)and allow rain, splashout, and Mother Nature to eventually bring it down.

 

[JasonLion]

You can add water at the same time you are taking water out. This approach uses slightly more new water but is quicker. You need to keep an eye on the water level as the rate of addition and subtraction will probably be different.

 

[JIMNSC]

Even more practical to me is to simply deal with what you've got (by keeping your Cl level up there)and allow rain, splashout, and Mother Nature to eventually bring it down.

Thanks Dave and Jason for your input. Dave I like best the part I quoted from your post. When you're almost 66 with a bad ticker you rarely are up to attempting what would have been "no problem" at 40. I've decided to compenstae for the high CYA with bleach, although I might try what Richard suggested recently and that is to begin using Polyquat 60 and maintaining th FC in the "3" range. I have purchased two quarts already but need to ask a question about the initial dosage for the PQ60 - maybe you, Richard or Jason would know. 13,230 gallons with a CYA of 150+. Would I use the initial treatment dosage on the bottle even though there is no way I have live algae at the rate of Cl I've been maintaining?

Mathmatically, Using the PQ60 would be more expensive than maintaining the Cl at 15ppm (I think) but I already have two bottles.

Jim

 

[duraleigh]

I have purchased two quarts already but need to ask a question about the initial dosage for the PQ60 - maybe you, Richard or Jason would know.

I'm too cheap to be a polyquat user so I'm no help. Jim, this point is often overlooked......maintaining higher Cl levels does not mean increased consumption necessarily, it only means maintaining a higher residual.

Holding your Cl level between 3-5ppm should be roughly the same consumption of Cl as holding it between 13-15ppm

 

[chem geek]

Yes, just follow the PolyQuat 60 directions on the bottle for initial dose and then weekly maintenance dose. They tend to be conservative with the dosage, but in your situation since we know that you won't have enough chlorine to keep away algae, I wouldn't skimp. For people like Carl who just use a small amount as extra insurance, then just a few ounces is fine since chlorine levels are normally maintained, but your situation is different.

I think that you will lose more chlorine from sunlight at the higher chlorine levels than lower levels with CYA constant. It is supposed to be proportional to the amount of chlorine in the water (dependent on CYA as well). However, with the very high CYA levels in your pool, the loss from sunlight should be relatively low even at the higher chlorine level. So the choice is up to you. We normally don't recommend PolyQuat 60 in place of chlorine, but there's nothing wrong with doing that -- it's just usually more expensive.

From a disinfection point of view, your pool will be fine since bacteria are far easier to kill than algae. The only exceptions are the bacteria that causes hot tub itch, and the protozoan cysts Giardia and Cryptosporidium, but all of these aren't handled even in pools that follow Ben's chart (and fortunately are rarely found in residential pools).

Richard