Cyanuric Acid at 75 ppm: What to do?

[JamesW]

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[mgtfp]

Because I swim daily, I prefer to have the chlorine level at or below 5 ppm

I also like to swim daily (at least once this thing they call summer finally arrives and those torrential rains stop). Because of that I prefer to have my chlorine level above 8ppm with my CYA of 80ppm and having an SWG.

As Newdude already pointed out:

The industry' is literally stuck in the 80s and haven't evolved with the times. Lots of science has advanced since then, including here. It's alot to process but read up and ask away at any time.

There are questionable opinions that the 80s brought some good things. But they certainly managed to hide away learnings first published by a chap called O'Brien and some of his mates in 1969 about the CYA-Chlorine chemistry. Essence of that his that most of the chlorine is bound to CYA where it is protected from UV, but otherwise does nothing. It doesn't do any harm to swimmers, but also doesn't kill any bacteria, viruses or algae. Unfortunately, these chlorinated cyanurates still show up as "Free Chlorine" in standard pool chlorine tests. Only a small fraction of what tests as FC, is actually "active" chlorine, or HOCl.

There are some sticky threads by chem geek, who really got to bottom of that all, in the Deep End going through the details.

The essence is, to maintain same amounts of HOCl at different CYA levels, the FC/CYA ratio needs to be kept constant. In other words, 8ppm FC at CYA 80ppm results in the same amount of HOCl than 5ppm FC at 50ppm CYA, or 3ppm FC at 30ppm CYA. This is the basis of the FC/CYA Levels, which details appropriate target FC for different pool types (the more constant and reliable chlorination with SWGs allows for lower levels), which levels you never ever want to slip below, and which levels are required to get an active algae outbreak under control.

Lots to read here in the Pool Care Basics, and even more in thousands of threads.

 

[mgtfp]

What is the advantage of an SWG?

Newdude already covered this. I just want to add that I really don't get how people manage to run pools without SWGs without going crazy. Without my SWG, I'd filled in that hole in the backyard a long time ago.

 

[Striving]

I also like to swim daily (at least once this thing they call summer finally arrives and those torrential rains stop). Because of that I prefer to have my chlorine level above 8ppm with my CYA of 80ppm and having an SWG.

As Newdude already pointed out:



There are questionable opinions that the 80s brought some good things. But they certainly managed to hide away learnings first published by a chap called O'Brien and some of his mates in 1969 about the CYA-Chlorine chemistry. Essence of that his that most of the chlorine is bound to CYA where it is protected from UV, but otherwise does nothing. It doesn't do any harm to swimmers, but also doesn't kill any bacteria, viruses or algae. Unfortunately, these chlorinated cyanurates still show up as "Free Chlorine" in standard pool chlorine tests. Only a small fraction of what tests as FC, is actually "active" chlorine, or HOCl.

There are some sticky threads by chem geek, who really got to bottom of that all, in the Deep End going through the details.

The essence is, to maintain same amounts of HOCl at different CYA levels, the FC/CYA ratio needs to be kept constant. In other words, 8ppm FC at CYA 80ppm results in the same amount of HOCl than 5ppm FC at 50ppm CYA, or 3ppm FC at 30ppm CYA. This is the basis of the FC/CYA Levels, which details appropriate target FC for different pool types (the more constant and reliable chlorination with SWGs allows for lower levels), which levels you never ever want to slip below, and which levels are required to get an active algae outbreak under control.

Lots to read here in the Pool Care Basics, and even more in thousands of threads.

This is interesting stuff. From what you are saying, having a CYA of 80 is not as bad as I thought. Thank you, and I'll be reading more.

 

[Striving]

Newdude already covered this. I just want to add that I really don't get how people manage to run pools without SWGs without going crazy. Without my SWG, I'd filled in that hole in the backyard a long te ago.

That's a powerful statement. Would love to do less work. I'll look into getting a SWG.

 

[mgtfp]

This is interesting stuff. From what you are saying, having a CYA of 80 is not as bad as I thought. Thank you, and I'll be reading more.

It certainly is manageable. Very easy - even desirable - with SWGs to make full use of the UV-protection benefits, but more challenging when manually chlorinating. And risky, because once you do get that dreaded algae bloom because life happened and you couldn't add chlorine for a couple of days, you are facing a SLAM Process at high CYA which requires lugging home a lot of liquid chlorine bottles.

With a SWG, the benefits of CYA around 80ppm outweigh the risks because your chlorinator work horse does the leg work of constant and reliable chlorination for you.

Without an SWG, TFP recommends lower CYA levels to reduce the severity of an algae bloom (i.e. make a SLAM manageable), that is more likely to happen with manual chlorination.

But without a pre-existing algae outbreak and when being diligent about maintaining target FC according to the FC/CYA Levels and never slipping below min FC, CYA 80 should be manageable while waiting for CYA to decrease by decay (slower in colder winter water) and dilution (hopefully faster in winter with more rain). Dilution only helps when draining water from time to time. Evaporating water just leaves the solids behind in the pool.

Doing a partial drain and refill is of course the faster and safer option, but when not possible due to water restrictions, then patience and diligence with FC should do the trick.

 

[Striving]

It certainly is manageable. Very easy - even desirable - with SWGs to make full use of the UV-protection benefits, but more challenging when manually chlorinating. And risky, because once you do get that dreaded algae bloom because life happened and you couldn't add chlorine for a couple of days, you are facing a SLAM Process at high CYA which requires lugging home a lot of liquid chlorine bottles.

With a SWG, the benefits of CYA around 80ppm outweigh the risks because your chlorinator work horse does the leg work of constant and reliable chlorination for you.

Without an SWG, TFP recommends lower CYA levels to reduce the severity of an algae bloom (i.e. make a SLAM manageable), that is more likely to happen with manual chlorination.

But without a pre-existing algae outbreak and when being diligent about maintaining target FC according to the FC/CYA Levels and never slipping below min FC, CYA 80 should be manageable while waiting for CYA to decrease by decay (slower in colder winter water) and dilution (hopefully faster in winter with more rain). Dilution only helps when draining water from time to time. Evaporating water just leaves the solids behind in the pool.

Doing a partial drain and refill is of course the faster and safer option, but when not possible due to water restrictions, then patience and diligence with FC should do the trick.

This is super helpful. I will be looking into a SWG. The one question I have at this point is, with a SWG, is CYA 80 ppm approximately ideal, at least during summer?

 

[Newdude]

The one question I have at this point is, with a SWG, is CYA 80 ppm approximately ideal, at least during summer?

It would entirely solve the problem. Not cheaply, but it would solve it.

However, it pays you back because tabs and bleach are outrageously priced and you won't be buying any for 3-5 years. (Except the occasional jug as previously discussed). So when you see the prices, don't get sticker shock. It's effectively buying all your chlorine upfront.

 

[Striving]

Hi Everyone,

My TF-100 kit arrived in the mail today, so I'm updating this post as promised.

As it turns out, my CYA reading is much lower with the Taylor test than PoolLab 1.0 (about 48 with Taylor vs 75 with PoolLab). Of course, the Taylor CYA test is a little subjective. I first settled on 50-60, but then retested in a few different locations in my home and had my wife a daughter make guesstimates. Ultimately, I settled on a little below 50. Assuming that is correct, I don't have a CYA issue or at best a minor one.

I also totally gave up on the Bio Active CYA Reducer. It did not lower my CYA level at all after two days, despite my following their instructions to a T. Moreover, my FC level dropped to about 2, so I was becoming worried about algae. I added enough liquid chlorine to raise the FC to about 5.5, which corresponds to the TFP target level for a CYA of about 48.

I also looked into SWGs. It seems the price range for a pool my size (~16,500 gals) is about $800-2,000, and it might pay for itself in chlorine savings over its lifespan. The main benefit may be less maintenance, and also, if I'm away for a week or two I'll have less to worry about.

I would love to have suggestions on SWG models. Besides pool volume, it seems climate plays a significant role in pool chlorine demands and therefore SWG capacity. Riverside, where I live, can get quite hot in summer, and it's super sunny, but the winters are mild. It's a dry heat though. I'm using a pool cover now to retain heat, but I have not decided whether I will use one in the summer. Riverside Climate, Weather By Month, Average Temperature (California, United States) - Weather Spark

Thanks, everyone, for all your helpful comments.

 

[mgtfp]

Good work

I can't give you much advice on specific US SWG models. Only, that we generally say to buy one that is twice the size it's actually advertised for. The lifetime of an SWG is pretty much proportional to the amount of chlorine it produces. A SWG double the size will last twice as long, but will cost less than double the price.

Also, the advertised max pool sizes usually require running the chlorinator 24/7 on 100%, which will not give you any breathing space.

 

[pjt]

it might pay for itself in chlorine savings over its lifespan

It will definitely pay for itself. But, it's about more than just money. It's about the massive convenience and time savings of a SWG.

settled on a little below 50

For intermediate values, round up to the nearest 10. Your CYA level is 50.

I would love to have suggestions on SWG models.

Do you have automation? If so, pick a SWG from the same manufacturer so your equipment can talk. If not, look at CircuPool. In any case, get a SWG rated for at least twice your pool volume.

(And fill out your signature when you have a minute.)

 

[Newdude]

about 48 with Taylor

Always round up. As such, it helps the test SO much to only fill to the 10s. There is no need to agonize over a 34 or 37 if they're both gonna be a 40.

In this case call yours a 50 and follow the appropriate target level on the FC/CYA Levels. Now. You want to never drop below target level, but during the peak season, or at times other than that, you may go through more FC a day than the chart allows for. If you see the pattern through regular testing that you are losing 4 ppm a day (for example), then you want to be dosing so that you don't fall below target after that loss. That's the name of the game, to always have enough chlorine.

The FC above target level is safe up to 40% of your CYA level, in your case right now, that's 20 FC. There is next to no leeway below, between target and minimum and it's a one way ticket to a swamp if it happens often.

 

[HermanTX]

Of course, the Taylor CYA test is a little subjective. I first settled on 50-60, but then retested in a few different locations in my home and had my wife a daughter make guesstimates. Ultimately, I settled on a little below 50. Assuming that is correct, I don't have a CYA issue or at best a minor one.

I suggest you follow this test procedure for CYA

1. Make your 50/50 solution using your pool water and the R-0013 reagent as per instruction.
2. Mix it and let it sit for 30 seconds per the instructions
3. Rather than looking down the tube at the black dot and pouring your mixed solution. I suggest you squirt enough in your tube to a specific mark - such a 100. Then look in the tube for the black dot. If you see it, then squirt in more mixture to the 90 mark, then look in the tube for the black dot. Continue this for each decade graduation (i.e. 80, 70, etc.)
4. On the one you cannot see the dot then the previous mark is your CYA level. So if you saw the black dot at 50 but not at the 40 mark then your CYA is 50.
5. This way you are not staring at the black dot constantly and seeing it regardless. I remember my teacher in grade school had us stare at a black dot for 60 secs and then look up and we saw that black dot everywhere we looked - it’s the same effect if you stare down that tube.
6. Also, by filling to each decade mark, you ensure that you do not try to interpret between the decade marks as the tube is logarithmic meaning that the graduations are not proportional so picking a number between 2 decade marks is not feasible

I also totally gave up on the Bio Active CYA Reducer. It did not lower my CYA level at all after two days, despite my following their instructions to a T.

There are numerous reports that this product does NOT work. great that you stopped using it. Agree that you really do not have a CYA issue if you are in the 60ppm range.

I would love to have suggestions on SWG models. Besides pool volume, it seems climate plays a significant role in pool chlorine demands and therefore SWG capacity.

There are 2 variables for a SWCG that you need to set to produce a set x amount of FC ppm. This is pump run time and % output of the SWCG. I see you have a 1hp WhisperFlo pump. Is this a single speed pump? If so, then you want to reduce the amount of time that runs as more run time means higher electrical costs. So you will need to increase the % output of the new SWCG to offset low pump run times. That would indicate that you should upsize the SWCG to give you more flexibility. With a 17k gal pool, you need a minimum 40k rated SWCG. You could even consider a 60k rated SWCG.

In the future, you could go to a variable speed pump which allows you to run at lower speeds for longer periods of time which is much more energy efficient than a single speed pump.

 

[Striving]

I like your suggestion for testing CYA with the Taylor kit. It makes a lot of sense, given that the estimate will be rounded up away.

Thanks for your help with the SWG too. I didn't realize the benefits of a much larger capacity generator.

I plan to eventually upgrade to a variable-speed pump. My current one is getting old, so when it needs service, I'll just replace it.

Thanks again!

 

[Striving]

Always round up. As such, it helps the test SO much to only fill to the 10s. There is no need to agonize over a 34 or 37 if they're both gonna be a 40.

In this case call yours a 50 and follow the appropriate target level on the FC/CYA Levels. Now. You want to never drop below target level, but during the peak season, or at times other than that, you may go through more FC a day than the chart allows for. If you see the pattern through regular testing that you are losing 4 ppm a day (for example), then you want to be dosing so that you don't fall below target after that loss. That's the name of the game, to always have enough chlorine.

The FC above target level is safe up to 40% of your CYA level, in your case right now, that's 20 FC. There is next to no leeway below, between target and minimum and it's a one way ticket to a swamp if it happens often.

Thank you for this information. I didn't realize rounding up was the standard practice, but it certainly makes sense given the subjective element of the measurement. By rounding up we are merely acknowledging that there is imprecision in the estimate, which is better than reporting to the single digit when the method is not capable of that level of precision (which I think PoolLab 1.0 does).

I'm a bit piqued by your comments on chlorine. Are you saying I should routinely overshoot the target level because no harm is done, and it's a preventive measure against algae in case of a sudden large drop? Until now, I never conceived of bringing FC to 20 unless I was slamming.

My chlorine has been holding very well recently since I started using a cover. It tends to change less than 1.0 ppm a day. However, sometimes the combined chlorine increases to 0.2 or even 0.4 when the cover is on, so I take it off for several hours on a sunny day to correct that.

 

[Striving]

It will definitely pay for itself. But, it's about more than just money. It's about the massive convenience and time savings of a SWG.


For intermediate values, round up to the nearest 10. Your CYA level is 50.


Do you have automation? If so, pick a SWG from the same manufacturer so your equipment can talk. If not, look at CircuPool. In any case, get a SWG rated for at least twice your pool volume.

(And fill out your signature when you have a minute.)

Thank you for all this help with the SWG. I don't have automation. In fact, my pump control looks like a relic from WWII. Is automation worth the investment?

I will look into a CircuPooL unit with a rating of at least 40,000 gals. They seem to be a little less pricy than some of the major brands.

 

[Newdude]

I'm a bit piqued by your comments on chlorine. Are you saying I should routinely overshoot the target level because no harm is done, and it's a preventive measure against algae in case of a sudden large drop? Until now, I never conceived of bringing FC to 20 unless I was slamming

Yes. 20 is a bit much, (but still safe). The point was to worry less about being 'high' and worry more about nearing minimum FC, due to all the leeway above target, and very little leeway below target.

 

[HermanTX]

I will look into a CircuPooL unit with a rating of at least 40,000 gals. They seem to be a little less pricy than some of the major brands.

There are many members that use this CircuPool brand with success. There are also several threads on this forum where the stated output of the SWCG (lbs CL per day) are embellished vs. reality. It is worth researching because they are less expensive but maybe consider purchasing the next higher model. They constantly run sales to "upgrade" to the next higher model for a modest fee.

 

[Newdude]

Also, switch to 10ml tests and each drop is 1/2 FC. The number before the decimal matters, not the number after the decimal.

For example. A 2.2 or a 2.5 are equally as sucky. An 8.2 or an 8.5 are great for most CYA levels.

Save yourself 2.5x the supplies by testing to .5