cost/benefit shocking pool

Jump to latest Follow Reply
It is my understanding that when CYA is added, it takes a while for it to show up on the test, which would certainly be an essential realization so as not to add too much out of ignorance.
Questions:
1) Although it does not show up for a while on the test, will its stabilization effect on FC take place immediately?
2a) TFP recommends CYA level of 30-50 ppm. With over 12 hours of direct sunlight in the summer, do I want to be near the 50 end, or perhaps even a little higher? (Here's where cost/benefit analysis comes into play again.)
2b) At what point is the "critical value" at which $ saved by not having to add as much bleach daily becomes outweighed by the "ineffectiveness" of the FC present (daily and when shocking)?
 
1) Give it 24 hours and then assume that it is all present. That isn't exactly true, but it works fairly well.
2) Start around 50 and see how things go.
3) For most pools it is with CYA around 50, but it does vary a little.
 
With higher CYA levels you eventually reach 2 points:

1st point is where if for some reason you get algae growth and you need to shock the pool and find that shocking is difficult or not practical at your high CYA levels, sure in an ideal situation that algae outbreak should never happen if you maintain your chlorine levels, but in the real world things happen, pump motors go out, storms blow gunk into the pool, etc

2nd point is where the CYA gets so high that even while maintaining relativley high FC levels in the pool that algae starts to grow anyway.
 
Thanks for the specific answers, Jason! :-D
Isaac-1 said:
With higher CYA levels you eventually reach 2 points:
1st point is where if for some reason you get algae growth and you need to shock the pool and find that shocking is difficult or not practical at your high CYA levels
Click to expand...
I understand the "difficult" in that shock level would be higher, but why would shocking be impractical?
Isaac-1 said:
2nd point is where the CYA gets so high that even while maintaining relativley high FC levels in the pool that algae starts to grow anyway.
Click to expand...
I assume this would be CYA=100+? (Which I would never dream of approaching!)
 
Ok, lets take your pool for an example, and lets assume a CYA level of 120 ppm, which is generally considered around here the extreme upper end of what can be maintained, according to the Chlorine / CYA chart your target FC should be 13.6 and your shock value would be 46.7 for normal algae and 68.4 mustard algae

Reaching shock level for mustard algae would require over 20 gallons of bleach even for a minor outbreak, and since loss to sunlight and CYA protection from sunlight is not a linear function maintaining shock level would require much more bleach than if you were at lower CYA levels. In addition all that extra bleach is going to be adding a lot of salt to your pool water (usually not a bad thing, up to a point) These extreme CYA levels may also effect the abliity to clear CC from the pool.

A far worse runaway sitation happens if you try shocking with dichlor since it adds both CYA and FC
 
Another issue, high CYA levels require high FC levels. If FC gets high enough the PH test becomes unusable. It isn't practical to maintain a pool without being able to measure PH.

To expand on what Isaac-1 was saying, it is not so much that maintaining shock level at high CYA levels is problematic, as it is that the initial amount required to get to shock level in the first place can easy be way more than you would have needed in total at lower CYA levels. Worse, that huge addition of chlorine will also temporarily shift the PH out of range. Expect you can't measure PH at high FC levels, so correcting for the PH shift is shall we say problematic. Yet another issue is that there is no reliable way to measure high CYA levels. CYA at 100 and CYA at 200 are very different things, yet the test results for those two are nearly identical. And lets not mention the extra time and reagents required to measure the FC level (which still needs to be done regularly).
 
Isaac and Jason, I thank you both for your good points. I think it's save to assume I will not be approaching those levels, though! I am, however, sure that I need more CYA than I currently have (around 20 ppm). I haven't looked at the directions on the canister (small bucket) of CYA I bought, but I know that sometimes directions on chemicals are not recommended here. What is the recommended method for adding CYA?
 
I searched the site for this for a few minutes, but I didn't find anything. This may be a dumb question, but for efficiency's sake, since 16 oz of CYA and 16 oz of washing soda have about countering effects on pH, and my pH is perfect at the moment, can I add them together, or do I need to get CYA where it needs to be first, then adjust pH as necessary?

Also, the CYA directions say to broadcast directly into the pool. (Just like Cal-Hypo directions, which I now know is not recommended). Does the same go for CYA? Should I dilute/dissolve in water first?
 
I can't help but wonder if the problem is related to the seperate meter on the well, is your water pipe from the house to the well made of metal or plastic? If metal you may have a ground loop going on.

ooops this went in the wrong window
 

Enjoying this content?

Support TFP with a donation.

Give Support
Never broadcast CYA into the pool. That will often damage the pool surface.

Trying to maintain the PH at some "ideal" level is counter productive. The PH is going to change. If you try to hold it in too tight of a box you will simply end up swinging it around and wasting chemicals. Let the PH wander (some) and only adjust it when it goes out of range.
 
I lost count. I was very frustrated. Probably around 80. If I had been able to focus more on it, I'm sure I would have used a lot fewer. I was only shocking at night, since my CYA was too low to seem feasible to shock during the day, particularly when I had to work, so I couldn't maintain shock level, and some nights I couldn't get to it because I was too busy with work, so I'm sure I lost some ground at times. Once I "gritted my teeth and bore down" on the project, it went a lot faster. I actually stayed up all night one night, jacked the FC level into the 30's (probably higher than it needed to be, but like I said, I was "over it") and called in sick at work the next day. I only used about 10 gal. that night, but I had already made some progress, albeit very inefficient, with the many gallons used prior to that. It really is a challenging task if you cannot devote 100% attention to it until it's "under control"! Next year I'll make sure I start on a Friday night (and I'll have some CYA hopefully) and go full force from the beginning!
 
I doubt you'll have this problem next year. Just make sure to close your pool properly utilizing pool school directions.

In my case I decided to not use a winter cover last year. Opening 4 weeks ago involved a quick vacuum of debris and a few jugs of bleach to shock. My FC level held above 16ppm for 2 weeks since the water was so cold. I have a little higher CYA due to the SWG so less is lost to UV exposure. My pool is now ready to swim as soon as the water gets warm enough. Today my FC is holding around 5ppm weeks from shocking it. Once it drops to 3 I'll turn on my SWG and all I'll need to do over the summer is periodically add acid to keep the pH in check.

iam4iam said:
I lost count. I was very frustrated. Probably around 80. If I had been able to focus more on it, I'm sure I would have used a lot fewer. I was only shocking at night, since my CYA was too low to seem feasible to shock during the day, particularly when I had to work, so I couldn't maintain shock level, and some nights I couldn't get to it because I was too busy with work, so I'm sure I lost some ground at times. Once I "gritted my teeth and bore down" on the project, it went a lot faster. I actually stayed up all night one night, jacked the FC level into the 30's (probably higher than it needed to be, but like I said, I was "over it") and called in sick at work the next day. I only used about 10 gal. that night, but I had already made some progress, albeit very inefficient, with the many gallons used prior to that. It really is a challenging task if you cannot devote 100% attention to it until it's "under control"! Next year I'll make sure I start on a Friday night (and I'll have some CYA hopefully) and go full force from the beginning!
Click to expand...
 
I started around 50 CYA. I brought FC up to 25 and added my CYA with a sock floating in front of the return. After the CYA was dissolved it was around 85 because I overshot a bit. I guess shock level should have been around 22 for that amount of CYA. It did stay above 22 for the first week. It stayed around 19 the next week, and then 16 the next. Cold water (50F-55F) really helps hold FC!

iam4iam said:
I'm surprised you only needed 16 ppm FC to shock with as much CYA as you must have for the FC level to hold so well.
Click to expand...
 

Enjoying this content?

Support TFP with a donation.

Give Support
You must log in or register to reply here.
Thread Status
Hello , This thread has been inactive for over 60 days. New postings here are unlikely to be seen or responded to by other members. For better visibility, consider Starting A New Thread.
Top Bottom
Back
Jump to latest Follow Reply