Shocking Pool Help

[Moondrus]

One week ago we change our pool over to SWG. Previously we had been paying someone to maintain the pool but I decided I wanted to start doing it myself. I purchased the TF-100 test kit and the K-1766 Salt test kit. We are using the AquaPure 35 SWG.

On Friday I did my first set of tests:
pH - 8.4
CYA - 60
CH - 450
FC - 0.5
CC - 0.5
TA - 90
Salt - 5400

The pool water is clear. The SWG was running at 50% so I increased it to 100% and ran it 24/7 for the next few days thinking that might help the FC. I also added Muriatic Acid to lower the pH and added Stabilizer to raise the CYA.

I tested again yesterday:
pH - 7.3
CYA - 90
CH - 450
FC - 0.5
CC - 0.5
TA - 90
Salt - 5400

So on the recommendation of a friend who has maintained a pool for a while I decided to shock the pool last night and run a OCLT. Based on the pool calculator it said I need to add 252oz of 10% Chlorine to raise the FC to 23. I dumped the chlorine in around 6:00PM and did a test at 10:30PM. The FC came back at 42. Any thoughts on why the FC are so high? Did I not give the chlorine enough time to mix with the rest of the pool water?

So this morning I did another test and the FC came back at 31. Is it normal to drop that much over night? Or did the chlorine just finally mix in the pool enough that the levels are finally leveling out? This is still much higher then it should be based on what the pool calculator is saying.

Do I continue to run the pool 24/7 with the SWG set to 0%? I assume I should continue to do OCLT tests until I don't see a drop in FC?

Any help would be greatly appreciated.

Thanks!

 

[Texas Splash]

Hello and welcome! Glad to see you have the TF-100. Well, you have a few things going on it would appear. Let's try to address some of those now:
- When you ran your OCLT last night, was the SWG on or off? It should be off.
- Also, here at TFP, we do not do a one-time "shock" to remedy a pool, we follow a "SLAM" via Pool School - SLAM - Shock Level And Maintain. You probably should get real familiar with that page.
- You are correct that during a "SLAM" the SWG stays off and pump on 24/7 until 3 SLAM criteria are completed.
- Hard to tell if what you added is what was actually required based on pre/post readings. Please add your pool info to your signature by going to the top of the TFP web page (just under the Pool School button) and select "SETTINGS". On the next page look to the left for a menu bar that says, “MY SETTINGS” and go to "EDIT SIGNATURE" to enter your pool and equipment info there. It will help us later.

Le's start there and we can try to get you some better guidance. Welcome to TFP!

 

[Moondrus]

Yes the SWG was set to 0% last night when I ran the test. I understand that there isn't a one-time shock. I have read over the "SLAM" page and I am very familiar with it.
Based on the three criteria I was already meeting 2 of them (clear water and the CC is at 0.5). This is why I was trying to to an OCLT. The pool is ~9000 gallons and plaster. I am not sure of pool pump but I know the SWG is a AquaPure 35. I will have to look when I get home from work today and update my signature accordingly.

 

[Texas Splash]

One thing I learned personally recently during my own OCLT is that if we over-shoot our SLAM FC, we will lose more than the 1 ppm on the OCLT. The water chemistry just isn't capable of sustaining that much FC over & beyond what's listed on the CYA Chart. Perhaps consider doing another OCLT this evening, but watch carefully the FC level to prevent over-shooting? Are you comfortable with the calculator? Any chance you may not have updated the pool gallon info at the top?

 

[Texas Splash]

Oh, and don't' forget to add your pool info so we can try crunch the numbers as well. We're kind of working blind right now.

- - - Updated - - -

Another comment on your original post, the chlorine had more than enough time to mix. 30 minutes is generally enough time. 4.5 hrs is plenty.

 

[Moondrus]

Yeah I am comfortable with the calculator. It is pretty easy to use. and I updated the pool gallons at the top. Based on your comment it isn't crazy that it dropped 11 FC overnight? I would assume that some of that was due to the fact that it might have not fully mixed with rest of the pool water. Also it has been really hot and dry over the past week so the pool has been sitting around 90-92 degrees and based on what I have read this can cause the FC to drop as algae is more likely to be present. I also was able to look up my pool equipment so I added it to my signature.

 

[Texas Splash]

The only other thing that comes to mind as I re-read your first post ... when you last tested the FC at "0.5", and CC at "0.5", that low FC may have already allowed an algae bloom to begin and you just couldn't see it yet (cloudiness). The organics were already thriving. That could explain why you lost so much FC as well the first night since the FC was fighting the organics. You may just need to maintain that SLAM FC level for a short time and run another OCLT in the next day or two and see how it works-out for you.

 

[Moondrus]

That was my initial thought that something had started to form and we just couldn't see it yet. So that was my plan. I was going to test it again this evening and do another OCLT and see where I am at in the morning. Hopefully things have stabilized and the levels come back the same. Thanks for the information!

 

[Moondrus]

So, I tested again last night and the FC were 21. I figured that was close enough to shock level so I didn't add anymore Chlorine to the pool. Tested again this morning and it was still at 21. So whatever was in the pool must be gone now.

What is the proper procedure to get the FC back down to the normal level? Should i keep the SWG at 0% and let them fall fast or should i turn the SWG on a low percentage so it doesn't drop below the normal level?

Thanks!

 

[Texas Splash]

Yes, just let it fall naturally. The sun will help there. I suppose you could leave your SWG at a reduced percentage, but however you chose to do it, just make sure you don't drop too low as the day goes on. Better to be safe (slightly high) than low. Congrats on the OCLT!