Shock amounts of chlorine and OCLT issues?

Jeff.williams

Gold Supporter
In The Industry
Jun 29, 2018
33
Montgomery, TX
Guys -

I need your help here... So, I skipped a week of pool testing. I tested yesterday evening late and found my values as listed: (see my logs as well)
FC: 2.5
CC: 0.0
PH: 7.8
TA: 60
CH: 375
CYA: 30
BOR: 45
Temp: 72
CSI: -.06

Now, here is the interesting part, I noticed a little green algae in places that are known to grow it if things get out range or something odd happens. So, I did a slam shock with the TFP app and it indicated, based on my current CYA levels, to add right at 4 gallons of bleach. I did this and after almost 2 hours of run time in high with all pumps and features on high to help facilitate mixing, my FC only rose to 7.5 and CC was .5. So, I used the app again and added 2 additional gallons of bleach (12.5%) before hitting the target of 13 (actually overshot it by .5 fo 13.5). This morning, before sunrise, I re-checked it and it did not move and the CC was 0. So, we have a successful over night chlorine loss test. I did take the PH down before all this and as a result lost 10 points on the TA but I am going to adjust this morning with about 45# of bicarb. My question is why did it take so much bleach to hit the slam value of 13.0 (13.5) when the app, based on current CYA, etc. indicated that I only need about 3.75 gallons of chlorine. I ended up putting 6 gallons of bleach in the pool to reach the 13.5 of FC. Now, I have Supreme plus and enzymes from Orenda in the pool, but other than that, nothing else. Is there something in the pool that used the chlorine to oxidize it possibly that fast? The water appears clear and no known issues. Any ideas? I have a chlorine injection system that I am installing now, or in the slow process of installing on the system to automate this stuff. I do not use trichlor and control CYA manually.
First, I thought that the size of the pool was off (gallons). I built the pool. I used a flow meter to fill it but, last night I second guessed the volumes I had recorded and used google maps and the measurement tool to find the total area in sq ft. I then converted to cubic feet and it came out to almost the exact total that I have. So, I have eliminated that possibility.

Any ideas!?!?

Best,
Jeff Screen Shot 2020-11-12 at 7.48.37 AM copy.jpg
 

tim5055

Mod Squad
TFP Expert
LifeTime Supporter
May 11, 2014
11,108
Franklin, NC
While you may have passed an OCLT, there are three factors to stopping a SLAM

- Pass OCLT

- Water is clear

- There is no visible algae

It's possible that the chlorine was reacting with the visible and unseen algae in the water. Clear water can still have a fair amount of algae in it.

Personally I'd hold it at the SLAM level for at least 24 hours giving the pool a good brushing.

A TA of 60 is fine and I wouldn't mess with it now.

As to the volume, I had to watch chemical additions and the effects they had for many months to dial in what I thought the real volume was. I was told 23,000 gallons and came in at closer to 21,000.
 
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Jeff.williams

Gold Supporter
In The Industry
Jun 29, 2018
33
Montgomery, TX
While you may have passed an OCLT, there are three factors to stopping a SLAM

- Pass OCLT

- Water is clear

- There is no visible algae

It's possible that the chlorine was reacting with the visible and unseen algae in the water. Clear water can still have a fair amount of algae in it.

Personally I'd hold it at the SLAM level for at least 24 hours giving the pool a good brushing.

A TA of 60 is fine and I wouldn't mess with it now.

As to the volume, I had to watch chemical additions and the effects they had for many months to dial in what I thought the real volume was. I was told 23,000 gallons and came in at closer to 21,000.

Tim,

One thing that stands out here is my ORP. I know that "we" TFP guys do not really use it but it becoming more and more of an issue and people are asking me for automation. I am installing a Sense and Dispense liquid chlorine and acid injection system on my pool and for now, I am using a floating ORP sensor, one made of gold and the other titanium to play with ORP. Both are reading in the mid to low 600(s) and I would think that I should be around 750 MV or so with FC this high unless something has the FC tied up... I just want to get this all dialed in so that I know what I am doing on future installs....
 

Mdragger88

Bronze Supporter
Jun 1, 2018
1,800
Hernando, Ms
Pool Size
26000
Surface
Vinyl
Chlorine
Salt Water Generator
SWG Type
Intex Krystal Clear
Maybe your bleach is not the strength listed (old stock, left in the sun etc)? Not uncommon late in the season.
Also I would definitely holdSLAM Process levels for 24hrs & follow the other slam protocols like brushing, vacuuming, checking light niches etc.
Slam is a process not a one time dump of chlorine w/ no mechanical action. If you aren’t thorough you may periodically fight algae on a regular basis as it’s always just barely being controlled.
 

JJ_Tex

Gold Supporter
Bronze Supporter
Jul 17, 2019
2,298
Prosper, TX (DFW)
Pool Size
13000
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-40
There are a number of reasons that your chlorine may not have hit the expected numbers, the most common are:
- Your pool size is not what you think (which you seem to have eliminated)
- Your Liquid Chlorine has lost some of its strength

Also, what the heck is Orenda supreme plus and enzymes.... and why?

Regardless of any of the above, the TFP way to get rid of algae is to SLAM. The process is in pool school, but you should get your FC to 12 and keep it there for several days to kill the algae once and for all. After that, keep your FC in the 4-6 range for your CYA of 30.
 
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tim5055

Mod Squad
TFP Expert
LifeTime Supporter
May 11, 2014
11,108
Franklin, NC
Tim,

One thing that stands out here is my ORP. I know that "we" TFP guys do not really use it but it becoming more and more of an issue and people are asking me for automation. I am installing a Sense and Dispense liquid chlorine and acid injection system on my pool and for now, I am using a floating ORP sensor, one made of gold and the other titanium to play with ORP. Both are reading in the mid to low 600(s) and I would think that I should be around 750 MV or so with FC this high unless something has the FC tied up... I just want to get this all dialed in so that I know what I am doing on future installs....
ORP doesn't play well with CYA in the water is about all I know. @JoyfulNoise or @JamesW may be able to help

Personally, I'm not a fan of automation based on automated testing. The sensors are just not accurate and robust enough to keep you from having to fiddle with things.
 

JamesW

TFP Expert
Mar 2, 2011
23,460
Their poolmath logs indicate 50 lbs of baking soda. I hope that they are not adding that much.
 

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JJ_Tex

Gold Supporter
Bronze Supporter
Jul 17, 2019
2,298
Prosper, TX (DFW)
Pool Size
13000
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-40
Wow, there is a lot going on in this tread that I'm trying to digest. First, a couple of clarifying questions:
1. Is this your pool, or did you build it?
2. If you built it, are you trying to solve for an automated chemical dispensing system for this client and others?

From there, I think you should attack the problems individually, in this order:
1. You mentioned Algae. Follow the SLAM process to solve that. If this is your home, that is easy since you live there. If you built/service it, that will be more challenging since you will need to be there 3-4 times a day at least to test, brush, and add chlorine.

2. Fix whatever issues adding 50lbs of baking soda did. By my math that just slightly raises the pH, but adds a whopping 70 to your TA.
Let us know what you really added and we can go from there.

3. Let us know what you are trying to do with the ORP/dispensing system and we will try and help.
 
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Jeff.williams

Gold Supporter
In The Industry
Jun 29, 2018
33
Montgomery, TX
Wow, there is a lot going on in this tread that I'm trying to digest. First, a couple of clarifying questions:
1. Is this your pool, or did you build it?
2. If you built it, are you trying to solve for an automated chemical dispensing system for this client and others?

From there, I think you should attack the problems individually, in this order:
1. You mentioned Algae. Follow the SLAM process to solve that. If this is your home, that is easy since you live there. If you built/service it, that will be more challenging since you will need to be there 3-4 times a day at least to test, brush, and add chlorine.

2. Fix whatever issues adding 50lbs of baking soda did. By my math that just slightly raises the pH, but adds a whopping 70 to your TA.
Let us know what you really added and we can go from there.

3. Let us know what you are trying to do with the ORP/dispensing system and we will try and help.

I built it, and it’s mine. It’s a monster with 5 VS950(s), a booster pump, a eti 400 condensing titanium heater, laminars, bubblers, water wall, parascopic fountain, infinity edge, and 16 led lights...

I am adding sense and dispense chlorine and acid injection. With the latest firmware, we now have liquid chlorine injection and acid injection. I am using the OmniLogic by Hayward...

I hit the wrong value in the app and it should have been about 25 pounds of bicarbonate not 50 and no, I haven’t put any in. TA has been creeping down due to constant adding of muractic acid for ph...
 

Jeff.williams

Gold Supporter
In The Industry
Jun 29, 2018
33
Montgomery, TX
There are a number of reasons that your chlorine may not have hit the expected numbers, the most common are:
- Your pool size is not what you think (which you seem to have eliminated)
- Your Liquid Chlorine has lost some of its strength

Also, what the heck is Orenda supreme plus and enzymes.... and why?

Regardless of any of the above, the TFP way to get rid of algae is to SLAM. The process is in pool school, but you should get your FC to 12 and keep it there for several days to kill the algae once and for all. After that, keep your FC in the 4-6 range for your CYA of 30.
Thanks ~
Orenda makes Enzymes, metal out, and phosphate control products. I have tested all 3...

Supreme plus is a borate conditioning agent...
 

Katodude

Silver Supporter
Aug 22, 2017
1,274
West Palm Beach/Florida
Pool Size
15000
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
Hayward Aqua Rite (T-15)
You seem to have a very nice house and pool. I might make one humble suggestion. Get a SWG instead of a chlorine injection system. I think you will like that much better. Also no need to haul chlorine anymore.
 

Jeff.williams

Gold Supporter
In The Industry
Jun 29, 2018
33
Montgomery, TX
I am considering the SWG... just odd that everyone is scared of them here now - when I was building them several years ago, they were a big deal and now everyone is back to chlorine... odd
 

Katodude

Silver Supporter
Aug 22, 2017
1,274
West Palm Beach/Florida
Pool Size
15000
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
Hayward Aqua Rite (T-15)
Ask most people around here once you have owned a SWG you will never go back.

Also worth mentioning that every time you add chlorine to your pool you add salt. So your pool eventually builds up quite a bit of salt. You might as well use it to make chlorine.
 
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