SLAM / Shock Problems

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B

bkrepfle

Active member
Jul 15, 2020
32
Talleyville, DE
Pool Size
7000
Surface
Vinyl
Chlorine
Liquid Chlorine
Hi All. I am a new pool owner this year. I have purchased an Inetex 18' x 52" circular above ground pool with a 2100GPH sand filter. This pool holds ~7000 gallons of water. Unfortunately, I had not come across TFP and pool school prior to initially buying the chemicals for it. What I have purchased is a 50lbs bucket of 1" chlorine tablets. After reading pool school, I am super bummed about this loss of money as I really don't want to continue using the tablets because of the eventual CYA issue. I also purchased CalHypo 1lbs shock for the pool. I've shocked / SLAMed 3 times now this year, and done because of the misleading notation of pool stores stating you should shock once a week, after rain, etc.

My first SLAM / Shock application I used 1lbs of CalHypo. The second time I used 3 lbs of CalHypo, and I found my pool unable to lower chlorine levels and had to perform a few sessions of drain/refill to get chlorine back in-line. My third SLAM / shock application occured on 8/26 and I am still off the charts on the FAC taylor test. I performed this SLAM because I did not add the chlorine tablets in time and FAC reached 0ppm. Adding new tablets was not bringing the chlorine level up either. It looks purple vs the red reading @ 10PPM. Another thing I noticed before, and on the last SLAM is that I had what appeared to be mustard algae on the bottom of the pool after application. Running the automatic vacuum appeared to have gotten rid of it and water is currently crystal clear. I'm not sure if this was just some calypo that had collected at the bottom of the pool, or if it was actually algae.

all of my levels/averages are listed below

Chlorine: 3 ppm
PH: 7.4 - 7.5
Alkalinity: 100ppm
Calcium: 225 ppm
CYA: 35 - 40

I performed drain/refill yesterday, just draining pool down to intake and letting fresh water run into the pool while doing so, and I am in the process of doing it again as today, it seems that chlorine levels are still extremely elevated. Below are my current test levels, and with my current CYA level I don't see why this chlorine is not burning off in the pool. There have been no tablets in the pool for 48 hours now.

Chlorine: (not sure, best guess 15 - 20ppm)
PH: 7.4
Alkalinity: 100ppm
Calcium 225 ppm
CYA: 30

I've checked into Pool School and tried to research as much as I could, please, if you are going to refer me to go back there, please specify a specific topic or page to review. In addition, I'm assuming I need to figure out how to get rid of the tablets and calhypo, and just start using liquid chlorine and I'll get away from all of these issues. Looking forward to responses, thank you in advance for reading my novel and providing any input/advice.
 
Are you using a color block test for FC? They are not particularly accurate. A FAS-DPD test kit would be a better choice. You can just add this to your existing Taylor kit. You just count drops with the FAS test. It is very accurate.
 
Hi mknauss;

I do understand the process, and read it yesterday, however, I do not have any liquid chlorine yet, and I am working with the materials I stated previously. I will definitely review test kits, it sounds like I need to get my hands on FAS-DPD test kit as DorsalSpine has suggested.
 
bkrepfle said:
I do understand the process, and read it yesterday,
Click to expand...
Be sure to focus on the Maintain, part. From your post, it does not imply that you were doing that. That you were dosing once, and done. But yes, you need a proper test kit to follow the Process regardless.
 
Hi Marty;

I am not sure how I'm not maintaining at the moment, since FAC has not dropped since I applied calhypo. My main questions for this thread are as follows:

anyone experienced with calhypo? If so, do these issues seem to align with that experience?

Why is my FAC not lowering with CYA only at 30?
 
Cal hypo is chlorine and calcium. When you add a certain amount, it raised the chlorine and calcium a certain amount. Nothing magic about it.

You cannot test at levels above 5 ppm TC. You need a better test kit.
 
To go back to your original question. The sun and organic material will consume your FC. The problem with "my FC doesn't drop" has more to do with your test method than anything else. Trichlor, cal-hypo, liquid bleach all contribute to FC and all will be consumed at any level of CYA. The trick is knowing the pros and cons of each.
 

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Thanks to both of you. I don't mean to come off brash, rude or anyhthing like that either, just frustrated with my situation, especially coming up on a holiday weekend where i have taken additional time off of work. In addition, I'd like to get the process down right so I can properly SLAM before closing the pool down for the winter. I think the main thing I need to do is get off of cal hypo and trichlor and swtich to bleach both for normal CH mgmt and for SLAM. I appreciate the info you have provided and will def look to add the FAS-DPD test kit. I figured I had gotten a good kit with the Taylor test kit, however, I am limited to that block test, which only goes to 10 or 12ppm on the chlorine scale if I remember correctly. Any suggestions on what to do with all of this trichlor I have? I'm assuming that shouldnt be thrown away, I would like to try to sell it somwhere to recover some of the money spent on it.
 
The Taylor kits are good kits. You just need the right one. I started with a Taylor 2005 which didn't have the FAS test. When I found this site I added the FAS test kit from TF Test kits. I've never been happier. We understand your frustration. Most of us ended up here due to frustration with pool store advice.
 
So, I was just reviewing the test kits, and my taylor kit I do have FAS-DPD. I have Taylor reagent #'s 1 - 3. 1 & 2 used for FAC and reagent 3 used for CC. The problem is the 9ml I fill and put the reagents in only has a color code match that goes to 10ppm. Would I need to mix the 9ml 50/50 with distilled water when testing higher levels, then multiply FAC by 2, or is there a completely different testing that you are referring to all together? I bought a taylor starting kit and had to fill in some of the reagents after I got it, but I can test FAS-DPD, PH along with acid/base demand, TA, CH and CYA.
 
The FAS-DPD test involves adding powder to the water sample (10ml for example). The water turns pink/red depending on the level of FC. You add the reagent one drop at a time until the water turns clear. At the 10ml sample size you take the number of drops and divide by two. Ten drops would be a FC level of 5. This is very accurate and works for any level of FC. No guessing matching colors. For extreme accuracy use a 25ml sample or for very high levels of FC you can use a 5ml water sample. You have to adjust the drop count according to the sample size. I don't have the numbers with me but they are listed in the directions.
 
Got my DPD test, as of this morning, below levels tested:

FAC: 2.4 ppm
CC: .2 ppm
PH: 7.5
Alk: 80 ppm
CH: 175 ppm

I did not test CYA today as I'm out of the reagent, but last test a few days ago, I had around 33 ppm.

My next question, it sounds as though I'm on the line of needing to SLAM, I also have a number of leaves starting to collect in the pool as I'm finding it harder to keep up with them now and I need to get them out. To SLAM with CAL HYPO, is that even recommended? Should I just get bleach to do it? Appreciate any responses that can be provided.

Additional question I have, as closure, and my first one, is right around the corner, it is recommended to "shock" the pool at closure. I'm assuming a SLAM would be better? Additionally, should the pool be closed at shock chlorine levels or is it preferred to let them drop? I believe my closing kit I got from in the swim contains a non-chlorine oxidizing agent in a styrafoam floater for the duration through the winter.

Appreciate any responses, and thanks for the help so far. FAS-DPD test kit rocks!
 
You typically round up for values of CYA. Even at 30 your FC level is too low. I'd hold your FC in the 5 -7 range if it was mine. A value of 2.4 FC suggests you are using the 25ml water sample size. This is good for accuracy but unnecessary for day to day use. The 10ml sample gives accuracy with .5 points and uses less reagents. I'd suggest using liquid pool shock (it's just concentrated bleach), either 10% or 12.5%. I bring my FC up to SLAM levels for a day or two right before I close.

www.troublefreepool.com

Closing an In Ground Pool

Winterizing a pool is essential for keeping your in-ground pool protected during cold-weather months. This Pool Repair guide will show you how to do it.
www.troublefreepool.com www.troublefreepool.com
 
Unless you replaced water or added stabilizer, your CYA will still be 30. Your CC is only 0.2. That is a very good number. Is your water clear? If so, follow the FC/CYA chart and add chlorine using Poolmath. You should be good to go. There is no need to "shock" the pool every week.

www.troublefreepool.com

The Free Chlorine and Cyanuric Acid Relationship

Managing your cyanuric acid and Free Chlorine levels is key to stabilizing your pool. Learn how these two items affect each other.
www.troublefreepool.com www.troublefreepool.com

And you definitely can use Cal Hypo powder for raising your FC.

If your water isn't clear, your will need to SLAM.

SLAM Process
 
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