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Thread: Question regarding adjust PH before starting SLAM

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    Question regarding adjust PH before starting SLAM

    My PH is really high, like 8.2. I just added acid, since I understand the PH needs to be lower before starting a SLAM. My question is: how long should I wait for the pump to circulate the acid before before retesting the PH?
    18 foot diameter, 52" tall above ground Cornelius pool, with vinyl liner, and resin wall caps.
    Roughly 7600 gallons
    Blue Wave "Sandman" Sand filter/pump, model NE6150. Pump is 1 HP
    Intex SWG, model # 54601E

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    JoyfulNoise's Avatar
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    Re: Question regarding adjust PH before starting SLAM

    30mins, especially if you brush the pool, should be more than enough time.
    Matt
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    Re: Question regarding adjust PH before starting SLAM

    Thank you. I should mention that I've been away from the house so much that I haven't been able to start the SLAM, but I think I'm ready to start, but have another question. I just checked my CYA level, and it's unusually low: 27. I thought last season, it was up around 70. (By the way, I have a SWG, but I haven't turned it on yet this season, as I want to SLAM first before doing that.)

    Does it makes sense that it could get that low? I thought you really had to drain the pool to lower it that much. I will say, I recently got finished repairing a stubborn leak in the pool jet inlet adapter (I have another thread here about that), I had to drain the water to the bottom of the hole that's behind the jet to work in it, so I guess that could explain part of the drop, but still, 27 is a big drop.

    Could the presence of algae be affecting my measurement? I read a tip here in another thread to use a coffee filter on the water before doing a CYA test, and that's what I did.

    Anyway, I guess with a measurement of 27, I should raise the CYA before starting the SLAM. I do have on hand over a dozen 3 inch chlorine tablets, which I know will raise the CYA level, plus as a bonus, the free chlorine it releases into the water should help kill the algae as well, so I guess I'll do that. I need to find out how much each tablet will raise the CYA by, but I know I have an old thread here somewhere that answers that question, so I'll go find that thread.

    I remember reading that the danger of SLAMing with not enough CYA is that the chlorine breaks down too quickly, causing the water not to retain enough free chlorine during the times between my checkups. (I like to check each morning and evening on the chlorine levels during SLAMing.) But the Chlorine tablets continually release chlorine, taking care of that problem.

    My idea is to maybe put one tablet in a day during the SLAM, and using the charts on this site, projecting what the CYA each day will be during the process, adjusting the free chlorine levels a bit higher each day to compensate for the ever increasing CYA, and at the beginning, while the CYA is still low, I suspect I shouldn't be worried about the quickly dropping free chlorine levels, because the ever dissolving tablets should compensate for that. By the time my last tablet is gone, the CYA should be high enough that the burn off of free chlorine will no longer be a problem.

    Still, I'm a little worried about starting the process right now and trusting my 27 measurement, because if it's wrong, will I be able to confirm that before dumping in my chlorine? I.e. can you reliably remeasure CYA during a SLAM in progress, would shock levels of chlorine interfere with that?
    18 foot diameter, 52" tall above ground Cornelius pool, with vinyl liner, and resin wall caps.
    Roughly 7600 gallons
    Blue Wave "Sandman" Sand filter/pump, model NE6150. Pump is 1 HP
    Intex SWG, model # 54601E

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    Mod Squad tim5055's Avatar
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    Re: Question regarding adjust PH before starting SLAM

    How are you testing that you got a CYA of 27?
    TFP Moderator 39 X 18 23,000(ish) freeform gunite; built 2007ish; Pentair Triton II TR100 600lb Sand filter; 2 HP Pentair pump with 2.2 HP AO Smith single speed motor; 2 skimmers, 1 main drain, 4 returns w/waterfall, Stenner 45MHP2 3GPD running@ 60% - 15 gal Tank; heated by the sun CYA 200+ when I started - 50 now. Dolphin Supreme M5 Pool Cleaner. Hot Springs SX Spa, 285 gallon

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    Re: Question regarding adjust PH before starting SLAM

    Quote Originally Posted by tim5055 View Post
    How are you testing that you got a CYA of 27?
    I have one of the test kits recommended by this site, and the large white capped bottle is labled "R-0013 CYA Reagent - 8 oz" The instructions say to do a 50-50 mixture of pool water and this, put it in a thin calibrated tube, adding it until I no longer can see the black dot in the bottom of it. That dot gets pretty dim, but I can't say it disappears completely until it got to the 27 mark.

    By the way, the pool calculator says I should add 10 3-inch pucks if I want to boost it up to 70 parts, which is a little alarming that I should need to add that much. But I do have that much on hand, so I guess I can go ahead and do that. I think I also read that the PH might get lower if I do that, but my pool seems to always have upward drifting PH anyhow.
    18 foot diameter, 52" tall above ground Cornelius pool, with vinyl liner, and resin wall caps.
    Roughly 7600 gallons
    Blue Wave "Sandman" Sand filter/pump, model NE6150. Pump is 1 HP
    Intex SWG, model # 54601E

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    Re: Question regarding adjust PH before starting SLAM

    Oh, here's another alarming development. Yesterday I added enough acid to theoretically lower my PH from 8.2 to 7.5, but I just tested it, and it's off the top of the chart, meaning over 8.2 (maybe 8.3). How can that happen? Adding acid should lower my PH. (I'm using a Taylor test kit, and I add 5 drops to a thin column of water, and compare the color to a chart.) Is it possible that having green water in my pool interfere's with my ability to measure PH? I did filter the water through an unused coffee filter before testing it.
    18 foot diameter, 52" tall above ground Cornelius pool, with vinyl liner, and resin wall caps.
    Roughly 7600 gallons
    Blue Wave "Sandman" Sand filter/pump, model NE6150. Pump is 1 HP
    Intex SWG, model # 54601E

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    Mod Squad tim5055's Avatar
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    Re: Question regarding adjust PH before starting SLAM

    You do not want to raise the CYA. CYA for a SLAM is 30 if possible. If you are raising the CYA while the SLAM is ongoing you never know what your actual shock level should be. No tabs, no granular shock - liquid chlorine only for teh SLAM.

    I have never seen a CYA tube with a 27 mark, they are in 10 point increments.

    Acid will lower pH. Your pH was high before and you added acid to lower it. You could have been well above 8.2 and you are still above 8.2.

    Be calm, one step at a time.
    TFP Moderator 39 X 18 23,000(ish) freeform gunite; built 2007ish; Pentair Triton II TR100 600lb Sand filter; 2 HP Pentair pump with 2.2 HP AO Smith single speed motor; 2 skimmers, 1 main drain, 4 returns w/waterfall, Stenner 45MHP2 3GPD running@ 60% - 15 gal Tank; heated by the sun CYA 200+ when I started - 50 now. Dolphin Supreme M5 Pool Cleaner. Hot Springs SX Spa, 285 gallon

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    Re: Question regarding adjust PH before starting SLAM

    Quote Originally Posted by tim5055 View Post
    You do not want to raise the CYA. CYA for a SLAM is 30 if possible. If you are raising the CYA while the SLAM is ongoing you never know what your actual shock level should be. No tabs, no granular shock - liquid chlorine only for teh SLAM.

    I have never seen a CYA tube with a 27 mark, they are in 10 point increments.

    Acid will lower pH. Your pH was high before and you added acid to lower it. You could have been well above 8.2 and you are still above 8.2.

    Be calm, one step at a time.
    Thank you for that advice. You're right there is no 27 mark it was about 7/10 tenths of the way from the 20 mark to the 30 mark, so I estimated 27 based on that. Okay, I'll go ahead and add more acid and check again. Maybe at that time, I should do another CYA check to be sure. Do I infer correctly that I should have at least a CYA of 30 before starting the SLAM though? I'm guessing one tablet would accomplish that, because I think it would raise it about 4 points. But to be safe I won't do that until I take another reading, unless you think even that's a bad idea.
    18 foot diameter, 52" tall above ground Cornelius pool, with vinyl liner, and resin wall caps.
    Roughly 7600 gallons
    Blue Wave "Sandman" Sand filter/pump, model NE6150. Pump is 1 HP
    Intex SWG, model # 54601E

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    Re: Question regarding adjust PH before starting SLAM

    Welp, after adding 16 ounces of more acid and waiting about 45 minutes, I retested. It's dark out, but I went out to my garage where I have whiter light (because I have flourescent light fixtures there). It looks like I overshot the mark, and my PH is at 7.2 (I was aiming for 7.4). But actually according to the sticky in this forum 7.2 is probably a better number than 7.4 for SLAMing, so that's good.

    Now, I retested my CYA, and now instead of 27, I'm getting 20.

    It's disillusioning that I could have lost so much CYA since last fall. I read stories here about people having trouble lowing it, and I seem to have opposite problem. Now that my PH seems good, what are people's opinion on my next step? I assume I should raise my CYA before doing anything right? I hear I should have at least 30 before starting a SLAM.
    18 foot diameter, 52" tall above ground Cornelius pool, with vinyl liner, and resin wall caps.
    Roughly 7600 gallons
    Blue Wave "Sandman" Sand filter/pump, model NE6150. Pump is 1 HP
    Intex SWG, model # 54601E

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    Mod Squad tim5055's Avatar
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    Re: Question regarding adjust PH before starting SLAM

    If you tested the CYA at just a hair under 30 in sunlight go with that number. Any CYA test results from artificial lighting is suspect. Assume 30 and begin your SLAM
    TFP Moderator 39 X 18 23,000(ish) freeform gunite; built 2007ish; Pentair Triton II TR100 600lb Sand filter; 2 HP Pentair pump with 2.2 HP AO Smith single speed motor; 2 skimmers, 1 main drain, 4 returns w/waterfall, Stenner 45MHP2 3GPD running@ 60% - 15 gal Tank; heated by the sun CYA 200+ when I started - 50 now. Dolphin Supreme M5 Pool Cleaner. Hot Springs SX Spa, 285 gallon

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    Re: Question regarding adjust PH before starting SLAM

    Thank you. I guess worst case scenario is that the chlorine drops too fast, which would give some evidence of too low a CYA number (I assume.) I'll start it tonight, and tomorrow I'll do my usual morning test, and for this first day only, maybe I'll do a mid-day test to see how the chlorine is holding up. I could post the results here, and maybe get an updated opinion if the drop rate is acceptable or not. As you say, if I'm really close to 30, hopefully the SLAM will go normally.

    I admit this CYA has always been the hardest number for me to measure, because it's hard for me to see exactly when that black dot disappears. I guess later on, if I want, I could get an independent free measurement via my local pool store. (Which thanks to this site, I never visit anymore. I love not being talked into buying stuff I don't really need, which is why I consider this website so valuable.)
    18 foot diameter, 52" tall above ground Cornelius pool, with vinyl liner, and resin wall caps.
    Roughly 7600 gallons
    Blue Wave "Sandman" Sand filter/pump, model NE6150. Pump is 1 HP
    Intex SWG, model # 54601E

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    Re: Question regarding adjust PH before starting SLAM

    Quote Originally Posted by Zindar View Post
    for this first day only, maybe I'll do a mid-day test to see how the chlorine is holding up.
    The object of the SLAM is to test and re-adjust the chlorine back to shock level as often during the day as you can. The only limitation is not to do it more than once an hour.

    The more times you test and adjust the FC back up to shock level the quicker the SLAM goes.
    TFP Moderator 39 X 18 23,000(ish) freeform gunite; built 2007ish; Pentair Triton II TR100 600lb Sand filter; 2 HP Pentair pump with 2.2 HP AO Smith single speed motor; 2 skimmers, 1 main drain, 4 returns w/waterfall, Stenner 45MHP2 3GPD running@ 60% - 15 gal Tank; heated by the sun CYA 200+ when I started - 50 now. Dolphin Supreme M5 Pool Cleaner. Hot Springs SX Spa, 285 gallon

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    Re: Question regarding adjust PH before starting SLAM

    Oh, oops. I've done a SLAM a couple of times before, and both times, it succeeded with checks only twice a day. Admittedly my CYA was higher back then, and the chlorine levels held pretty well. Well the good news is that starting last October, I now work from my house instead of an office, so I'll have much better and more frequent access to my pool to do checks on it. This weekend, I was away from home a lot, but I guess it's good I start on a Sunday night, since I'll be home most of the time all week long.

    One thing is, that it takes quite a few drops of the test kit to check FC levels while shocking, and if somebody were to check it 10 times a day, I could see them quickly running out of their test kit fluids. Then again, the charts say that with lower CYA, the needed FC level is also lower, and so less test kit drops will be needed, so I guess that's something. Actually at my CYA level, checking the water 5 x a day = roughly the same amount of test kit drops as checking a CYA 70 pool 2 x a times a day.
    18 foot diameter, 52" tall above ground Cornelius pool, with vinyl liner, and resin wall caps.
    Roughly 7600 gallons
    Blue Wave "Sandman" Sand filter/pump, model NE6150. Pump is 1 HP
    Intex SWG, model # 54601E

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    Re: Question regarding adjust PH before starting SLAM

    Here are some reference pics of the CYA test that I found helpful. https://www.taylortechnologies.com/C...P?ContentID=44
    TFP Moderator
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    Re: Question regarding adjust PH before starting SLAM

    Okay, last night I added enough chlorine bleach to raise my FC to 12 per the pool math, and this morning, to my pleasure I got up to see the water is mostly blue now (but maybe with a hint of green to it), so the bleach is definitely helping. But what I was surprised at is that my FC overnight has dropped to a 3. My memory is that during the night there's usually not much drop in FC because of the sun not being out.

    Question: is this drop because it was my first attack on the algae, and the algae has quickly eaten the chlorine, or should I be worried about my CYA level causing the big drop? I guess I can test this theory well enough by quickly raising it back to a 12 and see if the the drops continue happening this fast (now that most of the green is gone.) The good news is that since I work from home now, I can do much more frequent checks on the pool. But for now, I need to go run to the store to get more chlorine... I don't have quite enough on hand to raise it to a 12, and underestimated how much I should keep on hand.
    18 foot diameter, 52" tall above ground Cornelius pool, with vinyl liner, and resin wall caps.
    Roughly 7600 gallons
    Blue Wave "Sandman" Sand filter/pump, model NE6150. Pump is 1 HP
    Intex SWG, model # 54601E

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    Mod Squad tim5055's Avatar
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    Re: Question regarding adjust PH before starting SLAM

    Only two things cause FC to drop, UV from the sun and organics in the water being oxidized by the FC.

    As I said above, the object of the SLAM is to test and re-adjust the chlorine back to shock level as often during the day as you can. This is what kills and oxidizes the bad stuff in the water. The only limitation is not to do it more than once an hour.

    The more times you test and adjust the FC back up to shock level the quicker the SLAM goes.

    Tome to run over to WalMart or Dollar General for a bunch of bleach.
    TFP Moderator 39 X 18 23,000(ish) freeform gunite; built 2007ish; Pentair Triton II TR100 600lb Sand filter; 2 HP Pentair pump with 2.2 HP AO Smith single speed motor; 2 skimmers, 1 main drain, 4 returns w/waterfall, Stenner 45MHP2 3GPD running@ 60% - 15 gal Tank; heated by the sun CYA 200+ when I started - 50 now. Dolphin Supreme M5 Pool Cleaner. Hot Springs SX Spa, 285 gallon

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    Re: Question regarding adjust PH before starting SLAM

    Okay, I've bought more and added it back up to 12 ppm. By the way, I found where I read the stuff about the CYA, which is in the sticky on the top of this very forum:

    "It is important that the CYA level not be zero. If CYA too low, you will lose too much chlorine to sunlight, and the algae will be able to get ahead of you."

    This actually answers my question about last night. The drop cannot have been due to low CYA, because there was no sunlight. (I know you just said that only the sun and organics causes it to drop, but I was worried about the rate of drop being affected by CYA, and now I see that the CYA had nothing to do with the rate of last night's drop.)

    Interestingly, I think I may have added too much bleach last night. In the past, I've used the pool math calculator by simply entering the current and target levels, and my # gallons. Now, it looks like it's got a new variable: % of chlorine in the bleach. last night I used the default 6% it gives you, but my bleach is 8.25% chlorine. My local HEB grocery store sells 121 ounces of 8.25% chlorine bleach for $2.94. Oh well, it ate chlorine fast enough that probably no harm was done, but I've corrected my use of the pool math starting this morning.

    Here's another surprising quote from this forum's sticky.

    "Second, you need to know your CYA level. If you just got back from vacation you should know what the CYA level was before you left. If the pool has been closed over the winter (or longer), the CYA may have vanished over the winter"

    I didn't think it could just vanish like that - I've read other threads on this forum that says it can only lower through these 4 methods:

    1) splashing in the pool
    2) draining and refill
    3) backwashing
    4) a very slow process of oxidation (I don't know if they mean oxidation of the chlorine or of the CYA - I'm guessing the latter.)

    Though if it can just "vanish" as the sticky claims, it could explain why I've dropped down to 30 since then. (But I did do a small drain and refill, just enough draining to work on my jet inlet adapter, and maybe a couple of backwashings since last fall, so I'm sure that's part of what happened.
    18 foot diameter, 52" tall above ground Cornelius pool, with vinyl liner, and resin wall caps.
    Roughly 7600 gallons
    Blue Wave "Sandman" Sand filter/pump, model NE6150. Pump is 1 HP
    Intex SWG, model # 54601E

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    Mod Squad tim5055's Avatar
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    Re: Question regarding adjust PH before starting SLAM

    The "vanishing" CYA is generally in covered green pools over winter and it will almost always go to zero, not stop at 30. There is an anaerobic bacteria that consumes CYA and converts it to ammonia. If this had happened to you you would have an enormous chlorine demand, to the point that a lot of times it goes to zero as you pour it in the pool.

    For now you need to

    Test FC
    Adjust FC to shock level
    Repeat as often as possible.....

    Brush the pool once a day
    TFP Moderator 39 X 18 23,000(ish) freeform gunite; built 2007ish; Pentair Triton II TR100 600lb Sand filter; 2 HP Pentair pump with 2.2 HP AO Smith single speed motor; 2 skimmers, 1 main drain, 4 returns w/waterfall, Stenner 45MHP2 3GPD running@ 60% - 15 gal Tank; heated by the sun CYA 200+ when I started - 50 now. Dolphin Supreme M5 Pool Cleaner. Hot Springs SX Spa, 285 gallon

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    Re: Question regarding adjust PH before starting SLAM

    That's interesting info about the bacteria. By the way, I did do a quick brushing yesterday, planning on doing a better brushing job today. I'm about to go test it again and add chlorine if needed, because I'm about to go out on an errand for a couple of hours before coming home. (I actually have today, tomorrow, and Thursday off from work.)

    It's also cloudy today, so that might actually help me with chlorine usage. Or maybe not, as you mention UV eating chlorine, and I'm guessing UV can go through clouds (but not sure). It's not really important, as my test kit will tell me low it's getting.




    Editted to add: measurement shows a much smaller loss now since earlier this morning. It only dropped from 12.0 to 11.5, so I only had to add a little bit of chlorine. I guess the drop has slowed down due to the green being gone. Still blue cloudy, so definitely will be a while before I'm done.

    The bad news is I just discovered I'm getting very low on my FC testing bottle, and it might run out during the SLAM. I'm going to order more ASAP, and if I run out before the new test bottle comes up, I guess I'll sadly have to let the chlorine levels drop a little more than I'd like. (I can at least keep a normal amount of chlorine using my other test bottle, but that bottle is only valid for lower chlorine levels, not shock levels.)

    If the above happens, I'll have to resume the SLAM whenever I get the new bottle. I'm still glad I started it though, because I didn't want the green infestation to grow more than it already had, to the point where I'd have to do a lot of scrubbing to get it off. If I get lucky, the new bottle might show up in time before I run out, and maybe I won't have to suspend the SLAM.
    18 foot diameter, 52" tall above ground Cornelius pool, with vinyl liner, and resin wall caps.
    Roughly 7600 gallons
    Blue Wave "Sandman" Sand filter/pump, model NE6150. Pump is 1 HP
    Intex SWG, model # 54601E

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    Re: Question regarding adjust PH before starting SLAM

    I was able to order R-0871 drops, and it'll be delivered within a couple of days, so I may not have to interrupt the SLAM, fortunately.
    18 foot diameter, 52" tall above ground Cornelius pool, with vinyl liner, and resin wall caps.
    Roughly 7600 gallons
    Blue Wave "Sandman" Sand filter/pump, model NE6150. Pump is 1 HP
    Intex SWG, model # 54601E

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