how often to SHOCK ?

Jump to latest Follow Reply
i also discovered how critical the pH levels can be... one website states the lower the pH the more the species of chlorine ( or part of the CL atom) is more prevalent and vice versa. The lower the pH the more oxidizing power , the higher the opposite is true. but ideally 7.5 makes the CL works best.
I wonder when slamming if the pH should be at a little lower ( 7.3 ~ 7.4 ) to speed up or help oxidize the algae ( or whatever organics ) in the water
 
When CYA is in the water, the pH has very little effect on the chlorine effectiveness. The stuff you are reading does not take the CYA into effect.

First step of the SLAM process is lowering the pH to the low 7s, but this has nothing to do with the chlorine effectiveness. It is done to counter the temporary rise in pH caused by using so much bleach to raise the FC to SLAM level. When the FC drops again, the pH also comes back down.
 
before i slammed i lowered the pH to the numbers you mentioned. when adding bleach is there a way to predetermine or calculate how much the pH will rise proportionally to FC's going up?
I noticed the pool calculator mentions how much the pH will be lowered when using x amount of Trichlor or Dichlor.
Is there a way to find out in the same way adding bleach will raise the pH?
 
You are over thinking everything. Does not matter how much the pH goes up with the bleach. Bleach is effectively pH neutral.

With any CYA in the water, the chlorine effectiveness is not impacted when the pH is anywhere in the normal range for pools.

Just keep everything in the recommended ranges and the pool will be fine.
 
When you add a hypochlorite source of chlorine to the water, such as adding bleach or chlorinating liquid, the pH rises, but when the chlorine gets used/consumed, the pH comes back down because such usage/consumption is a net acidic process. This is why bleach is close to pH neutral in the long-term (there is some excess lye so it's not exactly pH neutral even when the FC drops back down, but it's close). That is not the same as using bleach for a SLAM because in that case you are raising the FC a lot so the pH will rise as well and you keep the FC high until you are done with the SLAM at which point the pH will drop back down as the FC gets lower. CYA's buffering effect on chlorine starts to lose its effect when you get to high FC levels, but the main reason we say to lower the pH before a high FC SLAM is to prevent metal staining or other side effects of high pH such as scaling.

You should stop reading other websites regarding pool water chemistry since a lot of what is written is wrong. As for CYA's effect on the amount of active chlorine at different pH, you can see this by comparing the "classical" graph all the other websites show vs. what really goes on in this post. With no CYA in the water, the active chlorine level drops by around 50% when going from a pH of 7.5 to 8.0, but with CYA in the water the active chlorine level only drops by 15%. This means that at normal FC levels having a pH of 7.8 is not a big deal at all and there is no need to have the pH at 7.2. Again, stop reading other websites about this unless they are peer-reviewed scientific papers in respected journals.

Your pH test in a Taylor or TFTestkits kit will be valid up to 10 ppm FC so it works fine for the FC/CYA levels you usually use -- it's only for a SLAM with high FC where the test may show a falsely high reading though usually in a SLAM the pH is higher anyway.

How much the pH rises when adding a hypochlorite source of chlorine depends on the TA, CYA and borates levels. If I assume 80 ppm TA, 30 ppm CYA and no borates, then a 10 ppm FC increase will have the pH go from 7.5 to 8.13 while starting at 7.2 would have the pH go to 7.54. A 20 ppm FC increase will have the pH go from 7.5 to 8.51 while starting at 7.2 it goes to 8.08. So this is why for a SLAM adding a lot of FC it's better to lower the pH first. When the FC comes back down, the pH will come back down as well.
 
Dolphin, I have to agree with Jason. You are way over-thinking everything. Nothing wrong with curiosity, but these guys have given you lot's of solid information. You are fretting over minutiae. Yes, it is good to be diligent and knowledgeable, and accurate...but this is pool chemistry, not a scientific study. Relax, and enjoy your pool for a while.
 
well thats just it - is running a pool a strick chem science or a 'Cady Shack' way of running a pool lol ( a chocolate bar in the water looking like ***).
i do like the science tho behind what you all mentioned that bleach is neutral.
I do like what chem geek has said.
I just feel its better to know more than not enough right?
I just like to know how things work - to get a better understanding of it.
but as was mentioned earlier.. testing now and then for 'any overnight loss' is one accurate method.
the other, lowering pH before slamming before the pH peaks at high FC's then falls back down.
I'll keep you guys posted...
So far 5 days into Slamming and the water is looking really good, still loss of chlorine and suff wisping on the bottom when brushed.
It gets better with every day
 

Enjoying this content?

Support TFP with a donation.

Give Support
for instance, i read somewhere ( i could give you the link) that below 7.5 pH, the Hypochlorite acid is less dominate but the Hypoclorous acid is. The latter is not as effective.
At 7.5, both are present and equal in the water.
also, wouldn't the pH lower, if more dirt ( bacteria laden dirt) enters the water? Since the micro organism ( not sure about algae) are ' - ' negatively charged?
if the water is more negatively charged would that indicate a lower pH?
And a domino effect could start right? the lower the pH the less effective the CL and of course, the lower the effectiveness , the more the presence of negativly charged organisms ( the stuff mentioned)
so it would be important to maintain a close to ideal pH at all times ?
And of course, maintain, as you mentioned, a CYA of 30 ~ 50 @ 4 to 7 FC mentioned earlier.
another noteworthy thing to mention from this website: below 7.5 the hypochlorous Acid ( the weaker of the 2 ) is more prevelent so when you test for FC's, youll get a high reading; falsly believing you have all the killing power of Hypochlorite Acid
this makes for good reading: http://blog.myronlmeters.com/tag/free-chlorine/.
 
last year, i didn't have a FAS DPD test kit like the TF 100 mentioned. I couldnt tell how much chlorine i had but i knew i had a truck load of caclium Hypo in the pool.
( i wasnt as knowledgeable back then). I couldnt understand why the pool remained cloudy, despite high levels of FC, vacuuming, cleaning the screens, brushing.
After 2 weeks, i figured naw, no algae or the like can exist in water like that.
so i decided one morning to work solely with MA. Added a cup (7,500 gal pool) n see what would happen. Almost immediately the water started to clear up.
So i waited a little added another cup , sure enough the clarity came down even more.
my CH was ok, it wasn t high to begin with, Adding the cal hypo actually brought it close to the ideal mark.
long story short, after adding cup after cup o MA( slowly tho, like every 2 hours and brush to stir in in), the water finally became clear.
The water had so much CL in it for weeks that i dont think i had to worry about overnight ppm loss.
This year, i sctrickly follow the SLAM method.
Right now, i'm 7 days in the Slam process. Tomorow moring if i dont have overnight loss, the slam will be over. The clarity is 97% (hard to see for turbidity) complete. if i do have greater or equal to 1 loss then ill have to wait another day but its progressing.
I think what also caused the problem is too high a TA. The problem was triggered the minute i started to add Baking Soda the water sloowly became cloudy. Thinking that it was just a calcium hardness problem, i figured it would go away.
the problem maybe the Test Kit testing for TA, either the reagents may have become too old and telling me to keep adding B.Soda.
my pH kept creeping on the high side. Whether i had a hint of pH lock, unfortunatly, i cant remember.
This time, i will pay way more attention and may have the water tested carefully to see where i stand against my test kit
 
dolphin said:
for instance, i read somewhere ( i could give you the link) that below 7.5 pH, the Hypochlorite acid is less dominate but the Hypoclorous acid is. The latter is not as effective.
Click to expand...
You really need to look at the links I put in my posts that I write for you (e.g. this post I referenced in this post above). It answers your questions. Below pH 7.5, there is more hypochlorous acid than hypochlorite ion, so you got that part right, but you said "the latter is not as effective" with "the latter" being the hypochlorous acid (in what you wrote) and that is incorrect. It is hypochlorous acid that is the effective disinfectant. However, as my links showed you, when CYA is in the water, the reduction in the amount of hypochlorous acid is FAR less as the pH rises and it is also less of an increase when the pH drops.

dolphin said:
At 7.5, both are present and equal in the water.
also, wouldn't the pH lower, if more dirt ( bacteria laden dirt) enters the water? Since the micro organism ( not sure about algae) are ' - ' negatively charged?
if the water is more negatively charged would that indicate a lower pH?
Click to expand...
pH and negative charges have nothing to do with each other in terms of the surface of bacterial cells having a negative charge. Bacteria themselves are NOT net negative. Their negative surface charge is balanced by a positive internal charge -- the cell surface molecules are polar. They do not have a net charge, but a charge separation. You are confusing the fact that hypochlorite ion is less effective because it is negatively charged so is repelled somewhat from the surface of cells while hypochlorous acid is neutral and looks very much like water so enters cells more readily.

dolphin said:
And a domino effect could start right? the lower the pH the less effective the CL and of course, the lower the effectiveness , the more the presence of negativly charged organisms ( the stuff mentioned)
so it would be important to maintain a close to ideal pH at all times ?
Click to expand...
The lower the pH the MORE effective the chlorine, though not by that much when CYA is present. Maintaining a close to ideal pH is not that relevant in terms of chlorine effectiveness -- again, going from 7.5 to 8.0 only has the active chlorine (hypochlorous acid) concentration drop by 15% when CYA is present compared to 50% when CYA is not present (though when CYA is not present, the active chlorine level is way too high). So again, stop reading other sources that are either wrong or half-true.

dolphin said:
And of course, maintain, as you mentioned, a CYA of 30 ~ 50 @ 4 to 7 FC mentioned earlier.
another noteworthy thing to mention from this website: below 7.5 the hypochlorous Acid ( the weaker of the 2 ) is more prevelent so when you test for FC's, youll get a high reading; falsly believing you have all the killing power of Hypochlorite Acid
this makes for good reading: http://blog.myronlmeters.com/tag/free-chlorine/.
Click to expand...
As for testing for FC, it not only tests hypochlorous acid and hypochlorite ion, but even more importantly it is mostly testing all the chlorine attached to CYA and that is the least effective form of chlorine of all of these. This is why the Chlorine/CYA table is so critically important to follow and is MUCH more important than worrying about whether the pH is 7.2 or 7.8 or 7.5.

As for that link you provided, there is also a lot of misinformation about ORP, so again I implore you to stop reading all the incorrect or half-correct or incomplete information you will find on the Internet. For example, the "unknown chlorine species" in Figure 2 in that link likely reacts with the dye and is probably chlorine that has been released from CYA. If you have specific questions, then ask the here, but please stop copying or referring to all the other information since we will spend all our time correcting it all when this information has been discussed ad nauseam many times on this forum. The Pool School gives you the net result and you can search this forum for accurate information from the mods and significant contributors.
 
dolphin said:
last year, i didn't have a FAS DPD test kit like the TF 100 mentioned. I couldnt tell how much chlorine i had but i knew i had a truck load of caclium Hypo in the pool.
( i wasnt as knowledgeable back then). I couldnt understand why the pool remained cloudy, despite high levels of FC, vacuuming, cleaning the screens, brushing.
After 2 weeks, i figured naw, no algae or the like can exist in water like that.
so i decided one morning to work solely with MA. Added a cup (7,500 gal pool) n see what would happen. Almost immediately the water started to clear up.
So i waited a little added another cup , sure enough the clarity came down even more.
my CH was ok, it wasn t high to begin with, Adding the cal hypo actually brought it close to the ideal mark.
long story short, after adding cup after cup o MA( slowly tho, like every 2 hours and brush to stir in in), the water finally became clear.
The water had so much CL in it for weeks that i dont think i had to worry about overnight ppm loss.
Click to expand...
I don't know how you can attribute anything to the lowering pH that cleared up the water since you didn't have a proper test kit so can't know at all what your true CH, TA and pH were and you might have had calcium carbonate over-saturation causing cloudiness. You said you used a truckload of Cal-Hypo and that is known to cloud the water due to the high CH and raising the pH when added. Lowering the pH will help to clear up that cloudiness. No mystery there.

This is why we emphasize using a proper test kit. Otherwise, you will really have no idea what is going on with your pool. Thank you for getting a TF-100 test kit. That will make a world of difference.
 
of course! the kit gives you a proper basis or proper starting point and able to monitor the critical phase of Slamming.
The kit i had is a not a Taylor test kit but a version of it in a foreign country called Spin. the company attempts to mimic the exriact look of the taylor kit.
I tested the TA CH ( and of course cant test for higher FC above 4 properly with it).
The kit told me i had 150 ~ 180 ppm CH a TA of 80~100. but im beginning to doubt the results it gave me.
As you said the carbonates where way to high.
So l may have to find a quality test kit that will test ALL elements correctly ( TA,CH,pH,CYA ).
it maybe, down here the temp never gets below 80 F, so its possible the reagents are useless!
I may have to bring the sample in to get a proper reading but who's to say that their reagents are bad as well
 
The only test the high FC affects is the pH, which will read artificially high.

I have to say half the time I have no idea what you are talking about or where you are getting your information :scratch:

Why would you think that the temperature being above 80 degrees would make the "reagents worthless"???
You should always store the test kits indoors out of the sun to prolong its life.
 

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