Trying to SLAM

[jonallen356]

I’m a first time pool owner. Specs should be in my signature, but it’s a 32,000 gallon chlorine pool with a vinyl liner.

I got the pool opened and got all values up to normal levels, but was having a hard time getting FC above 4. Did an overnight loss test and it dropped from 4ppm to 2ppm overnight.

Decided to SLAM. I put in the recommended 6 bottles (121 oz.) of 6% bleach around 8pm. Tested at 9pm and the pool was only up to 4ppm. Added another 4 bottles, tested at 10pm and it is still at 4.

I cannot figure out how six gallons of bleach only raised the FC by 2 ppm and then 4 gallons did essentially nothing.

Can anyone tell me what’s going on?

 

[jonallen356]

I’m using the TF-100 test kit.

 

[Razorhog]

My guess is the bleach is going away because it is oxidizing something. How does the water look? What kit are you using to test the water?

 

[jonallen356]

My guess is the bleach is going away because it is oxidizing something. How does the water look? What kit are you using to test the water?

The water looks pretty clean. Slightly hazy in the deep end. Some dark algae or something seems to be collecting around the wrinkles in the liner.

 

[Razorhog]

I’m using the TF-100 test kit.

Read my mind! Put that test kit in your signature
You are adding bleach after sundown so the only explanation is that there are bad guys in there eating it up. Or I guess you could have some really old bleach. But if it is being lost due to oxidation, you are doing it right - just gotta keep it at SLAM levels until it stops getting used up.

 

[Razorhog]

The water looks pretty clean. Slightly hazy in the deep end. Some dark algae or something seems to be collecting around the wrinkles in the liner.

There's your answer. Hazy water and especially dark stuff on wrinkles in the liner = algae. Since the water is relatively clear you shouldn't have a terribly hard time defeating it, but keep up the SLAM. The M is the most important = Maintain that shock level. Post a full set of test results when you can. Need to know the other numbers, especially CYA.

 

[mknauss]

Can you post a full set of test results?

 

[Razorhog]

As a side note - last year when opening I had serious algae. I put in bleach to bring the pool to shock level, waited 30 minutes, FC = 0. Brought the pool to shock level, waited 30 minutes, FC = 0 again. Etc.. This cycle repeated about 5 times before I read any FC. Losing FC rapidly when starting a SLAM is normal, it will get better. The more you can babysit the process in the early stages, the faster the process goes.

 

[jonallen356]

Working things out, buying stock in bleach, but these are the results I'm sitting at presently. I think I'm good to go. Just need to sit on it, test every few hours and keep that FC level up until I can hold it stable overnight.

FC = 16
CC = .5
TC = 16.5

PH = 7.5
CH = 75
TA = 110

CYA = 35

 

[jonallen356]

So I'm questioning now whether my SLAM is done. Overnight it dropped from 19 to 17.5, which is right above the threshold. But that test doesn't seem 100% accurate to me, because I'm not fully confident when the solution is completely clear versus slightly pink. Any advice you can offer?

 

[Richard320]

I think the record here to complete a SLAM on a greenish pool is three days. But that guy set his alarm clock and got up every couple hours through the night to brush and test and backwash and all. Typically it takes a week or so, maybe two if the pool was a real sludge pit with layers of soggy compost on the floor. As I read it, you started on Wednesday, so it's too early to really complain about the length of the process.

Do you have a light? Do you have a ladder? Both of those are famous lurking spots for algae. Have you brushed inside the skimmer throat? It's easy to miss since the brush on the pole won't go in.

Sounds like you're close. The chlorine losses should be minimal at this point. You say CYA is 35, so we round up to 40, which makes shock level 16 FC. Check every three or four hours and brush everything again. Maybe empty out the baskets, so the bleach isn't trying to oxidize any leaves or twigs. Vacuum. Just stay the course and you will be rewarded. And with a tiny bit of luck and some diligence, you will never have to go through this again.

And as for your thread title....