couple questions from a newbie about CYA, chlorine, leaf stain

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Some updates guys...

so i did the overnight test (7 hours), and the FC started at 11 and ended at 8.5. so looks like a slam is in order. im starting it now, trying to get FC up to 31, with pump running. will stop when the criteria are met.

one side question....kinda random but was curious.
lets assume that algae is gone and CYA Is 80.

if i get my pool FC up to 30 vs lets say 10. will my FC loss be constant in these two scenarios? for instance, at 30, if i lose 1ppm per day, i will end up with lets say 25 after 5 days. at FC of 10, will it also go to 5 after 5 days? will the loss between the two situations be the same?
 
The loss is a percentage of the FC level, the absolute loss will therefore be higher at higher FC.

Make sure to lower pH before you start right down to 7.2. Adding a large amount of chlorine to get to 31 will have an impact on pH that needs to be compensated before you start.

Once FC is back down where you started, pH will also be back down (plus increase due to CO2 outgassing that occured in the meantime). But while maintaining high FC, pH will remain elevated. One of the effects of high pH is that FC loss to UV is higher (due to the higher proportion of hypochlorite ion that is more susceptible to UV than hypochlorous acid), an effect that is not that significant at normal maintenance FC levels, but more pronounced at SLAM FC.
 
oh ok gotcha on the ph.

one clarification on the chlorine drop test. i added the R0870 powder and then when i add the R0871 solution drop by drop, it says "count each drop until the solution tuns back to completely clear". so at first is a red color, then as you get more and more drops in, it turn pink, then lighter pink. well at some point, the water turns sort of a light yellowish color when i put it against a white background. i wouldnt call it completely clear but its not pink or red either. as i keep adding drops, the color of the water doesnt change. is this normal?
 
eugchen said:
one clarification on the chlorine drop test. i added the R0870 powder and then when i add the R0871 solution drop by drop, it says "count each drop until the solution tuns back to completely clear". so at first is a red color, then as you get more and more drops in, it turn pink, then lighter pink. well at some point, the water turns sort of a light yellowish color when i put it against a white background. i wouldnt call it completely clear but its not pink or red either. as i keep adding drops, the color of the water doesnt change. is this normal?
Click to expand...
Add drops until the color does not change and subtract the last drop. If drop 5 it turns from pink to light yellow and drop 6 the color stays the same, use 5 drops as your test result.
 
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Click to expand...
will do, thanks!

so once im done with slam and i bring FC down to normal levels (9-11) for me, should i just check my chemicals once a week? (ph, FC, CC, alkalinity, calcium, CYA). is that the normal procedure?
 
eugchen said:
will do, thanks!

so once im done with slam and i bring FC down to normal levels (9-11) for me, should i just check my chemicals once a week? (ph, FC, CC, alkalinity, calcium, CYA). is that the normal procedure?
Click to expand...
the pool eats fc every day whether you play with it or not - so you must make sure it gets fed BEFORE fc ever falls to minimum FC/CYA Levels lest nasties will grow 🤢 & you’ll be behind the 8ball.
The average fc loss for a residential pool depending upon the season/uv/batherload is anywhere from 1-5ppm/day.
Generally a good idea to dose to high target 🎯 or a scootch higher so you have plenty of wiggle room before reaching the no no zone between doses. Testing fc/Dosing daily at first is recommended to get a feel for how your pool behaves depending upon your current conditions. Depending upon how quickly your ph rises you may need to test this every day/ every couple days as well until you get a feel for what to expect & what it takes to keep your ph in the 7’s.
The rest of the parameters don’t change that frequently so weekly or so testing is sufficient unless you do something that would change them like adding ch, cya or adding/exchanging water. You do need to know your TA to properly adjust your ph.
 
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so i started my SLAM last on Sunday evening at 7pm. today is Tuesday at 2:00am (second night with slam). i tested it earlier at 645pm and i counted 68 drops (FC = 34, CC = 0). now at around 2am, i counted 77 drops = (FC= 38.5, CC = 0). does this make sense?

about 20-30 minutes prior to 645pm, i did put in about 3/4 gallon of liquid chlorine but the pumps were on, and i used the net to jostle the water around before checking at 645pm. could this be the reason and that the FC 34 was actually higher?

was my SLAM test basically worthless?
 
Usually 30min should be enough to mix the chlorine in and get a good reading. Do you have a VS pump? If yes, on which speed is it running?

I'm thinking that you are going through a whole lot of test reagent, and counting errors are probably also becoming quite big. I'm tending towards using a 5ml water sample for testing while FC is that high, with a test resolution of 1ppm per drop. You can for example use a syringe to measure 5ml. Yes, test resolution is not as good, but it also doesn't help if you run out of reagents half way through the SLAM.

And with that many drops to count, the smaller number of drops (with less counting error) will actually compensate for some of the lost test resolution.
 
eugchen said:
so i started my SLAM last on Sunday evening at 7pm. today is Tuesday at 2:00am (second night with slam). i tested it earlier at 645pm and i counted 68 drops (FC = 34, CC = 0). now at around 2am, i counted 77 drops = (FC= 38.5, CC = 0). does this make sense?

about 20-30 minutes prior to 645pm, i did put in about 3/4 gallon of liquid chlorine but the pumps were on, and i used the net to jostle the water around before checking at 645pm. could this be the reason and that the FC 34 was actually higher?

was my SLAM test basically worthless?
Click to expand...
It was late when you wrote this...did you mean OCLT was worthless? In a word, yes.

Now to reasons.
  1. As @mgtfp indicates, using a 5ml sample during SLAM, where 1 drop = 1 FC will save reagent. We still recommend the 10ml sample for the OCLT.
  2. Waiting 30 minutes is typically just fine for adding and testing, during daily maintenance and when you are trying to get an accurate pool volume. For OCLT, I'd wait 1-2 hours before testing.
  3. My experience is that a SLAM with CYA of 80 *CAN* be done, but it will be difficult and take a lot of chlorine. It also takes a lot of reagent, and requires MANY drops during testing that introduces errors. It may be better to replace another 35% of your water and get CYA down to 50. It will be an easier SLAM and require less liquid chlorine. Reducing CYA also reduces testing error.
  4. Finally, there are many techniques that impact test accuracy. You want to clean your vial with alcohol and dry it out, hold the bottle vertical, squeeze the bottle only enough to get the drop to form and drop under its own weight. If you rapidly squeeze drops out, then tend to form smaller drops, making your drop count higher. Take a view of this video...
 
Yes that is a variable speed pump.

Yes, you should reduce the RPM. You are consuming 1836W...yikes.

If you have to heater (or solar) and no SWCG, then you can run it at any speed you want.

700-1100 RPM would be a nice place to start.

You run your pump for a reason. Mix chemicals, heat, filter, skim, run SWCG. Without SWCG, solar and Heater, there likely are no flow requirements. The only other consideration is skimming action. 7-1100 may not get the skimming you desire. You will have to play with that. Maybe you run 7-1100 RPM for 20 hours and run a higher RPM for 4 hours with RPM high enough to skim. There are no hard and fast rules. It is about achieving the outcome with skimming, filtering and mixing you require.
 
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The reason I asked about the VS pump was that if the pump had been on low speed, then 20-30min would clearly not have been enough. On high speed, 30 min should usually be enough. You were probably much closer to 20min. The Overnight Chlorine Loss Test article says "at least 30min", so go rather longer than shorter. I still suspect a testing error as a major contributor.

A SLAM at CYA 80 is no fun...
 
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*OCLT hack

With a VS pump, run it all night on low RPM to save yourself 30 mins of sleep in the AM. The $0.33 (?) it costs is. worth. every. last. penny.
 
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so couple questions...

i completed my SLAM a few days ago (SLAM level of 31) and now bringing my FC back down to 10ppm (for CYA of 80).

im measuring FC each day at sunset to see how much loss i incur each day.

i ended SLAM with 28.5ppm. (im using 5ml solution and each drop is 1ppm)(i came up with 28.5 cause i wasnt sure if the final drop was 28 or 29, so split it down the middle).

DAY 1 after 24 hours - 22 (this represented a 23% loss)

DAY 2 after 24 hours - 23 reading on first result, thought it was odd, so did it again and got 20.


QUESTION 1 -
is this normal for the error on 5ml to be this much? between 20 and 23 is a 15% error? im being careful, using dropper vertically.

QUESTION 2 -
i see i have extra POOL TIME SHOCK MAX BLUE in a cabinet and was wondering what this is. it looks like the strenght is 72%, which is alot stronger than liquid chlorine. is this just a way to get chlorine levels way up? and does it increase CYA?

this is the product.
www.homedepot.com

Pool Time MAXBlue2 10 lbs. Shock (10-Pack) 30010PTM - The Home Depot

Pool Time Shock MAXBlue2 is a fast-dissolving, 6-in-1 algae fighting pool shock formula that kills all types of pool algae and protects against frustrating algae growth. This unique granular formula clears
www.homedepot.com
 

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