Is it worth it having a high cya?

[consoleman]

Ive been using the tfp method for about 4 years now. I always kept cya to about 60ppm which would require me to buy alot of bleach for an entire week during the hot Houston summer.

I just replastered my pool and the mfg recommends 2-3ppm FC and 30ppm cya during startup. I find myself adding half a gallon each day to bring it up from 0 or 0.5 fc to 3 fc. Is there a downfall to letting fc drop that low?

 

[BasicTek]

At 60 CYA you should be targeting 7-9 FC with a minimum of 5 per the CYA/FC chart. The downfall is you could have organics in your water (even if clear) that are eating your FC the level is not high enough to prevent growth.

 

[Jimrahbe]

C,

With a CYA of 30 ppm, your very minimum FC needs to be at least 2.. See this chart... [FC/CYA][/FC/CYA]

And the lower the CYA, the faster the sun will burn it off..

Thanks,

Jim R.

 

[consoleman]

Well right now i have 30 cya so i target 3.5 fc. My fc should never drop below 2.2

If my cya were 60 cya i would target 6.8 fc and fc should never drop below 4.4.

My point is that whether i keep my cya at 30 or 60 and maintain the proper fc when adjusting every evening. During the hot days fc will still go below the "min fc levels" regardless of which cya i have

So what is the actual benefit of having a 60 to a 30 cya?

 

[BasicTek]

Sorry I misread and through you were already at 60. I can tell that my FC demand decreases at 80 CYA vs 60 (I estimate FC demand in my pool at 60 up to 2.5 per day and at 80 only 1.5 max) Of course every pool is different but 60 should have much lower demand than 30

 

[jblizzle]

During the hot days if your FC is dropping below the minimum then your target is not high enough. The most important thing is to keep it above the minimum at all times. I'm also not really sure where you got those recommended levels with the decimal places. I thought everywhere that we presented targets were rounded.

 

[jblizzle]

The higher the cya, the lower the percentage of FC you will lose to the Sun. Even though your target FC might be higher; with the higher cya you should actually be losing fewer ppm's each day to the Sun.

 

[consoleman]

jbizzle,
Since we have similar gallon amounts and sunny temperatures, what do you keep your cya and target fc at?

I just remember feeling like 60cya was not protecting my fc enough because it would drop below the min fc levels. Tried many OCLT and passed them. I always check my pool from 7to8pm.

 

[consoleman]

I used the values with a decimals from a thread on here. I have the correct chart printed at home

 

[jblizzle]

Moderators seems to be the worst at following our own advice sometimes

I really do not have any good historical data to provide. This summer I feel like I was losing a lot of FC to the sun my CYA is 40-50ppm. And I think Joyfulnoise and I have both been seeing our CYA drop in the heart of summer, so I keep having to bump it back up. I keep working to get it up to 60ppm ... next year I will go back to a SWG and have the CYA up around 80ppm.

 

[consoleman]

I do remember having to bring my cya up but i figured it was due to the water i had to keep adding.

I just dont see the benefit in having a high cya if it still goes below the min fc because of the sun. I could raise the target fc higher but then im losing at least 5 fc just to keep it above min fc.

If i have good clear water and have organisms that eat my fc like basictek says. Would that show up in my cc levels?



. Id rather have a low cya but i risk having organics in the water

 

[bordelond]

I just dont see the benefit in having a high cya if it still goes below the min fc because of the sun. I could raise the target fc higher but then im losing at least 5 fc just to keep it above min fc.

Hate to pimp my own thread, but I've just recently discovered and resolved an issue with lowering CYA levels. My CYA dropped from 60 in early June to 30 last week. Back in June, I only needed to add 2 ppm of chlorine every night to keep the TC levels in line. As summer progressed, I noticed my TC dropping (I test before adding) and started adding 4 ppm of chlorine daily. As of last week, even that wasn't enough chlorine -- the lower CYA level left my chlorine susceptible to sunlight burnoff. Accordingly, I started having cloudy water -- the very start of an algae bloom, perhaps.

Snapping my CYA back up to 50 and then slamming the pool has straightened the water out right quick over the past few days. Now I know that in this New Orleans climate - and probably yours as well - higher CYA helps a lot.

 

[Oly]

I suggest you test in the early morning and evening for a week or so and see for yourself the drop in FC at your current CYA level.

I am of the opinion that there is a sweet spot for CYA with a goal of lower required daily sanitation FC requirements (and lower SLAM FC) and protecting your FC from sunlight degradation. I expect differences for each pool based upon sun exposure and temperature but keeping sanitation levels in the TFP zone is the most important part with the amount and cost of the treatments the second factor.

I slowly brought my CYA up after a drain/refill and observed a slight reduction, maybe 0.5ppm in daytime FC drop as I increased my CYA from 20 to 30ppm. My FC loss during the day is about 1ppm and I add a minimum of 40oz of 10% for each 1ppm FC.

The proper test kit allows you to dial in your pool chemistry when you begin to look at data trends. Keep a data log. I am looking forward to testing into the Fall/Winter and observing the effect of lower temperatures and solar radiation on the FC loss per day.

 

[pookiesunshine]

Oly's idea is good. my chlorine usage is half this year vs last with an increase of approximately 10 ppm cya.

 

[Mickey Moose]

Dallas, TX, 26k gallons, CYA 40, full sun. Here is a 30-day chart of ounces of 8.25% bleach added (daily). Target FC is 7. I will raise my CYA a small amount but need to do a small drain first due to high CH.

 

[JoyfulNoise]

I target 80-90ppm CYA in the summer. When my CYA drops below 60ppm, my FC starts to fluctuate wildly. I also tend to keep my FC between 3-4ppm which is not in line with TFP SOPs so, like most parents, I'll expect you to do as I say, not as I do. I do get very high CYA loss over the hot summer months which is not unusual in hot arid climates with lots of UV. I've also tracked down some technical literature which leads me to believe that my combination of high heat and SWG is what is destroying my CYA at a higher rate than most; I've gotten CYA loss rates as high 10-15ppm/month (well within the measureable range on the melamine test when tracked over several months).

Raising CYA should lower daily loss but you should be careful to keep good track of your FC levels and shoot for consistency. With an SWG, that's easy; dumping bleach by hand, not so much....

 

[Oly]

Dallas, TX, 26k gallons, CYA 40, full sun. Here is a 30-day chart of ounces of 8.25% bleach added (daily). Target FC is 7. I will raise my CYA a small amount but need to do a small drain first due to high CH.

View attachment 68293

Thanks for the graph MM. A few questions.
Is the line through the middle the trend line averaging your application amounts?
Why the large fluctuations between daily application amounts with rates bouncing around from 2 to 8 X?
It would be interesting to see the FC test results that correspond to the actual application amount data.

 

[Autonoz]

My CYA is 80 and I have a FC drop of about 2-3 PPM during a hot sunny day in Arizona. On a cloudy day its around 1-2 PPM. My overnight is rarely anything. Your original question was what is the difference between high or low CYA if your going to still lose the same amount or more at lower levels. My answer would be, if your pool did get algae the amount of chlorine to shock it would be much higher. That's just a novice's reply.

 

[Mickey Moose]

Thanks for the graph MM. A few questions.
Is the line through the middle the trend line averaging your application amounts?
Why the large fluctuations between daily application amounts with rates bouncing around from 2 to 8 X?
It would be interesting to see the FC test results that correspond to the actual application amount data.

Yes, that's an average trend line.

Dosing variances are due to 1) slightly erratic weather, relative to normal, that we've had recently and 2) varying bather loads (some days the pool is not used, other days a couple-few people while others days I've had parties). Beyond that I don't know. I have been thinking of starting a new thread to discuss this. Obviously I'm now not the only one seeing it.

Here is an updated chart - ounces by volume of bleach added per test (as you saw before) is the red line, the blue line is FC. Sorry that this view is not real usable - I've been meaning to update my site such that I can optionally display either log charts and also optionally display the values as percentages.




Since the above chart doesn't work too well here is a different view that maybe will help you. Same time frame as above. The blue line is FC and red is FC loss. They should always mirror each other and in cases where they don't (about two-thirds over to the right you can see there's a blip where they don't) it's due to me making a change in my pool vs when the data was captured. So, in this case I changed my Target FC before capturing the data. You can disregard those couple of days and know that's simply not the norm.




The data goes way beyond the charts you've seen. I don't want to let the cat out of the bag with what all I did and how I did it but here's a teaser...




Cheers.

 

[Oly]

Data is both beautiful and mischievous. I am getting an idea now of how this works (I think) and am looking at both the red "additions in oz" of the first graph and the blue "FC in ppm" in the second graph and assume the data points represent the same day on the X axis correct? If so then this should a reflect a ppm FC response from your Cl applications. For example take the 1st data point in the top graph (155oz addition), now which data point on the bottom graph FC blue line is the response to the chlorine addition and how much time elapsed? Any way you can add a second Y axis and expand the FCppm data range from 1-7 over the top of your oz of additions range 20-180?

Keep the cat in the bag if you can.