How much chlorine do I need to kill algae, given these parameters?

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Just re-read Slam to get some clarification. It says to have enough LC on hand to raise to SLAM level at least twice. To me, that appears to mean that since FC may drop, depending on amount of contaminates including bacteria, phosphates and algae, and if it does you need to add LC to hit SLAM level possibly only as little as one more time, or until 3 specific conditions are met, one of which is overnight FC dropping no more than 1 ppm. That means it is possible that SLAM can be completed in just a few days, depending upon level of contaminates, correct?

Also, what is the max FC level you can swim in? I read somewhere that the FC can be higher if CYA is higher, so with low CYA 3ppm FC is fine to swim in, as is 13ppm if you have high CYA. Is that true or is that hogwash?
 
How does the cost of a reverse osmosis filter service compare to a drain and refill? Google says someone in the Sacramento area is charging $550 for 25000 gallons which is close to your pool size.

Also, don't all your posts need a Prop 65 warning on them?
 
You need your chlorine at 39 to do the SLAM. Raise it and keep it there until you pass the 3 criteria.
 
What about the success I've seen thus far? Is it really moot? Sorry for all my dumb questions, and what might SEEM as reluctance (I really am taking to heart what's all been said here), but as I'm trying to wrap my head around what needs to be done, seeing such quick and significant improvement already is what's giving me pause on doing the SLAM. All the text that says I must drain my pool to get my CYA down because how high I need to get my FC level to SLAM also concerns me. Is 39 FC really that high? What are potential negative impacts of that? Will such a level be hard on my 25 year old plaster, grout or any of my equipment? If so, should I do something lower, like 29 or 30, or has something like that already been tried, so I absolutely MUST hit 39? I ask this last question because, I can't recall where, but I read something that said to kill algae, your FC should be BETWEEN the high end of your target level and SLAM level.

And, if someone could chime in on my question about how high FC can be to swim in, that would be great. Is it something as simple as target range being the max, based on CYA level?

Thanks again, everyone!
 
You can do less than a SLAM. It's your choice. This isn't me being sarcastic, I just want you to understand the ownership is yours as to whether is works. You are asking us if we think less than a SLAM is OK. And we are recommending a SLAM. Anything less will have less likelihood of working long term.

Must you hit 39 - no, you can hit whichever number you wish. But know that you are not SLAMing if you don't hit the SLAM level.

Anything at or below SLAM level (on the high side) is safe to swim and safe on plaster.

FC loss will be rapid at high FC levels. Much faster than lower FC levels.

You will not be able to test pH above 10 FC.
 
I have a question:

Why not try properly performing the SLAM Process to completion? Then, after having that experience under your belt, you have a far better foundation with which to start experimenting. You're treating your extremely limited experience and single limited data point (added chlorine, visual change) as something worth as much consideration as years of experience by thousands of members of the site, which when put like that I think you can agree is hardly reasonable. Completing a SLAM will give you a better understanding of what we are talking about and why we suggest what we suggest.
 
Howdy neighbor... I get the that draining the pool is not cost effective, I am in the same market. I think you can limp along until you get to the winter rains that will dilute your pool anyway. You didn't mention what temp your pool is at in your initial post. The warmer the water the harder it is to control any algae. Luckily the temp is going to start dropping in the Sac area into the more pleasant Indian Summer temps.
I like the suggestion made to see if you can do a SLAM to completion with your current CYA. It wouldn't hurt to kill off all your algae before the winter kicks in. And just keep brushing. you will likely end up with some discoloration or roughened areas of plaster even after the black algae is gone. I noticed my local Walmart has LC on sale.. likely due to the end of the pool season.
Also fill in your equipment specs in your signature. It helps us figure out what you need. for example if you are running a SWG, then you only need to get to the 60-80 CYA range.
 
bmoreswim said:
You can do less than a SLAM. It's your choice. This isn't me being sarcastic, I just want you to understand the ownership is yours as to whether is works. You are asking us if we think less than a SLAM is OK. And we are recommending a SLAM. Anything less will have less likelihood of working long term.

Must you hit 39 - no, you can hit whichever number you wish. But know that you are not SLAMing if you don't hit the SLAM level.

Anything at or below SLAM level (on the high side) is safe to swim and safe on plaster.

FC loss will be rapid at high FC levels. Much faster than lower FC levels.

You will not be able to test pH above 10 FC.
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This is exactly the information I was looking for. So, thank you. And, don't worry, I don't hink you're being sarcastic; I actually appreciate your straightforward candor. But, I do have one additional follow-up question to your statement regarding not being able to rely on a PH test above FC level of 10. Not intending to be sarcastic (back at ya), but does it matter? I mean, do I need to care about PH during a SLAM? In case it matters, I don't know why, but my PH has ALWAYS been just about neutral, no matter what is done or not done, and regardless of time of year.

Oh, and what did you mean by it's safe to swim at or below SLAM level, "on the high side"? I only see one SLAM level on the chart, although I do see a range under "Target" level.
 
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Donldson said:
I have a question:

Why not try properly performing the SLAM Process to completion? Then, after having that experience under your belt, you have a far better foundation with which to start experimenting. You're treating your extremely limited experience and single limited data point (added chlorine, visual change) as something worth as much consideration as years of experience by thousands of members of the site, which when put like that I think you can agree is hardly reasonable. Completing a SLAM will give you a better understanding of what we are talking about and why we suggest what we suggest.
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Thanks for chiming in. I did not mean to imply that my limited experience was worth AS MUCH consideration than combined years of experience of thousands of people. You know how sometimes, for some reason, things shouldn't work but end up working? Like the person I read about that has a CYA over 200, runs FC at 5ppm, yet never has algae and has crystal clear water. According to the science promoted on this site, that just isn't supposed to be possible. Yet it's working for that person. This stuff happens outside of pool chemistry, too, like the person with a rim on their car that has a flat spot on the barrell. Technically, no matter what you do with a tire mounted on such a rim, that car should not be driveable. Yet, if a tire itself also happens to have a similar imperfection, if you position the tire just the right way, you can offset the flat spot on the rim with the imperfection of the tire, and now the wheel asembly is round.

My limited experience just means I don't have a lot of exprience; it doesn't mean I don't understand what everyone is saying, and what I've been reading on this site for years. I was just wondering if it's possble that because I had been running FC so low at 1.5 for years, could the sudden jump to 11.5 be enough to "shock" algae that's been perfectly comfortable at 1.5 for all these years? I've been asking this because I thought the impact of the sudden change is supposed to be the important aspect, and not necessarily just the numbers themselves. And, FC from 1.5 to 11.5 is a 1000% sudden change. Is there something to that theory, or is it a scientic fact that algae simply will not die at an FC level of 11.5? I mean, regardless of CYA level, isn't FC FC? What I'm trying to say is, at 100 CYA I might need to add WAY more LC to get 11.5 than someone with a CYA of 30, but isn't 11.5 11.5 no matter how much LC I needed to add to get there? And, I thought you only need 7.5% of CYA in chlorine to sanitize, yet I went 50% more than that 7.5% by jumping immediately to 11.5% (an bumped last night to 14%).

If everyone understands what I am saying, and that it doesn't matter what improvement I am seeing because it won't hold up, and I need to SLAM at 39, then I will SLAM at 39.
 
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mguzzy said:
Howdy neighbor... I get the that draining the pool is not cost effective, I am in the same market. I think you can limp along until you get to the winter rains that will dilute your pool anyway. You didn't mention what temp your pool is at in your initial post. The warmer the water the harder it is to control any algae. Luckily the temp is going to start dropping in the Sac area into the more pleasant Indian Summer temps.
I like the suggestion made to see if you can do a SLAM to completion with your current CYA. It wouldn't hurt to kill off all your algae before the winter kicks in. And just keep brushing. you will likely end up with some discoloration or roughened areas of plaster even after the black algae is gone. I noticed my local Walmart has LC on sale.. likely due to the end of the pool season.
Also fill in your equipment specs in your signature. It helps us figure out what you need. for example if you are running a SWG, then you only need to get to the 60-80 CYA range.
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Hello back! Sorry to hear you're in the same "if you want more water, give me your firstborn, along with an arm and a leg" market! My pool temp is about 85, no heater. As of this morning, algae has retreated an incredible amount, indeed leaving behind rough patches of plaster and remnants in those pores, which I have been repeatedly brushing over, and am watching very carefully. The only slimy stuff left as of this morning, were small patches I missed in the grout lines of the tile here and there in my initial and previous brushings. And, I can see just how the slimy layer protects the algae; the tiny patches I missed look like prime algae specimens, whereas the bigger patches that I brushed correctly are all disintegrating. I took care of those tiny patches though, this morning.

I originally thought I might monitor this progress carefully, and at the first sign of slowed progress, SLAM it. I am not scared of the SLAM process; in fact, it sounds darned easy. Nor am I afraid of the cost of the LC, compared to the cost of water where I am. In fact, since my pool appears to increase by approximately 2.5ppm per gallon of 6%, if I use the Walmart bleach that's only $36 to get to 39 FC from where I am now, and because right now my pool seems to drop 2.5 over 24 hours, if I have to add 1 gallon every day for a week that's only another $21, and that's only if I NEED to go an entire week. I'm just the type of person that doesn't like to use more chemicals than absolutely necessary, if I don't have to. That said, if everyone says I, without a doubt, will aboslutely need to SLAM at 39, SLAM I will. I just want to be sure I've given myself enough opportunity to hear from someone who says less worked for them. For what it's worth, I have seen pools with much, MUCH more black algae than I have had, if that matters. And, if I had it like the ones I saw, I would SLAM without hesitation. The amount I have had come back every summer I could live with. But, I noticed that in the past few seasons, it's been getting worse, and can see that if I didn't do something differently, I would eventually end up with one of those horror stories, which I don't want to happen.

Oh, and I could've sworn I filled out my pool stats, perhaps I didn't put it in the right place. I did have trouble after registering, and got banned from the site right out of the gate due to some kind of bug. Perhaps that had something to do with it. I will go enter it again.
 
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Yep it will get worse.. up to the point its uncontrollable. My neighbor was in such a state and refused to deal with it when it was dealable, then it was so bad they had to replaster the pool when the new owners bought it. We (the TFP community) know that if you try to limp along.. it will bite you in the rear eventually. There is story after story about it on this site.

So, what the folks here have found is the SLAM process is not just a shock but a sustained level of chlorine that will kill all the algae in the pool. And a test that confirms it. Sure you can "shock" in the short term but that doesn't confirm you killed "all" the algae. A SLAM properly carried out to its conclusion will do that.

So your call, I think it would be best to SLAM now then you have a pool that will be easier to manage going forward. Especially with a high CYA you're kind of teetering on the brink.

And while I am at the pool proselytizing ... have you considered retrofitting your pool with an SWG.. it makes pool maintenance life so much easier, IMHO
 
MrLeadFoot said:
This is exactly the information I was looking for. So, thank you. And, don't worry, I don't hink you're being sarcastic; I actually appreciate your straightforward candor. But, I do have one additional follow-up question to your statement regarding not being able to rely on a PH test above FC level of 10. Not intending to be sarcastic (back at ya), but does it matter? I mean, do I need to care about PH during a SLAM? In case it matters, I don't know why, but my PH has ALWAYS been just about neutral, no matter what is done or not done, and regardless of time of year.

Oh, and what did you mean by it's safe to swim at or below SLAM level, "on the high side"? I only see one SLAM level on the chart, although I do see a range under "Target" level.
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It only matters if you need to know what your pH is. ;) Correct to generally avoid pH during a SLAM since you can't test accurately. I guess I what I was getting towards is, you might be at this a while if you don't actually SLAM, so therefore it could be a long time where you wouldn't be able to test pH.

By "on the high side" I meant safe to swim at or below SLAM level on the upper end and (but didn't say) above your target range on the lower end. I didn't wan't to make my statement imply you could have 0 FC and it was safe to swim in because it was less than SLAM level. So there is an upper limit to safety and a lower limit. I was referring to the upper limit of safe.
 
mguzzy said:
proselytizing
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That cracked me up! You're doing a good job, just so you know! ;)

Seriously, though, I already am near a re-plaster. It's been 25+ years. The surface is rough in some places, which is perfect for the algae.

Thanks for setting me straight between the difference of a "shock" vs. a SLAM.

And, what do you mean I am "teetering on the brink" with my CYA levels. What is this "brink" you speak of, and possible issues if I teeter to the wrong side?
 
bmoreswim said:
I guess I what I was getting towards is, you might be at this a while if you don't actually SLAM, so therefore it could be a long time where you wouldn't be able to test pH.
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Ooooh, good point! I didn't think of that part of it. Sounds like a SLAM works quickly, and will be less work in the long run, huh?

By "on the high side" I meant safe to swim at or below SLAM level on the upper end and (but didn't say) above your target range on the lower end. I didn't wan't to make my statement imply you could have 0 FC and it was safe to swim in because it was less than SLAM level. So there is an upper limit to safety and a lower limit. I was referring to the upper limit of safe.
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Thanks for the clarification. Just all this talk about 39 being so darned high scared me. I didn't want my flesh getting eaten should I fall in during the SLAM.
 
I've often see us, meaning TFP, say that 39 is high. And relatively it is high compared to any normal FC level. But aside from bleach cost, inefficient use of FC (more rapid loss at high levels) and therefore more frequent dosing perhaps, it's not an issue in and of itself.
 
MrLeadFoot said:
That cracked me up! You're doing a good job, just so you know! ;)
...
And, what do you mean I am "teetering on the brink" with my CYA levels. What is this "brink" you speak of, and possible issues if I teeter to the wrong side?
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glad I make somebody laugh :D ... I meant that so much of your CL is bound up with the high CYA you have to maintain a higher CL level for it to be effective. and its easier to let it slip... in case you haven't seen this chart.. it gets called out all the time: FC/CYA Levels
 
bmoreswim said:
I've often see us, meaning TFP, say that 39 is high. And relatively it is high compared to any normal FC level. But aside from bleach cost, inefficient use of FC (more rapid loss at high levels) and therefore more frequent dosing perhaps, it's not an issue in and of itself.
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I thought someone said any given pool with a nominal CYA level will drop 2.5 FC overnight. Mine dropped 2.5 in 24 hours and my CYA is 100. So, while it initially cost me more in LC to get to my proper target range, maintaining it sounds the same as the person with the lower CYA. Or, am I missing something here?
 
MrLeadFoot said:
I thought someone said any given pool with a nominal CYA level will drop 2.5 FC overnight. Mine dropped 2.5 in 24 hours and my CYA is 100. So, while it initially cost me more in LC to get to my proper target range, maintaining it sounds the same as the person with the lower CYA. Or, am I missing something here?
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A pool will lose 2-4 ppm during the DAY from the suns UV rays. It should lose minimal FC at night.

Higher FC levels will lose some additional chlorine from oxidation. So the loss curve is not linear.

Thus the daily maintenance dose of chlorine will be a bit more if you are maintaining a high FC level due to your high CYA.
 

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