SLAM not making much sense

[Mavven]

Hey all, well.... I'm at it again. Opened to a crystal clear pool, wife helped me take off winter cover. I totally messed up and let a huge chunk of debris from the cover in the pool. Pool went from crystal clear to cloudy blue.

I'm very familiar with the SLAM process, as I did it last year. I have a 17,000 gallon 27ft round AGP SWG (not running during SLAM) 2HP 2spd pump. No ladder in the pool, lights etc. Just one return jet and widemouth skimmer.

Here's where I'm baffled. I use a Taylor kit to check my FC. I'm at about 40-50ppm CYA so I'm keeping my SLAM FC at 18ppm. I'm using 12.5% liquid shock. So last night my FC was @ 19.5 ppm @ 6:30 PM. This morning it was @ 15.5 ppm. Pool is crystal clear, I have scrubbed the walls and using the Dolphin Edge around the clock. I obviously have contaminants in the pool if I'm losing 4ppm overnight. Very windy nights and cold. Not sure that would affect anything.

Here is where I'm baffled. My pool is roughly 17,000 gallons. Every year I use the pool math calculator and it's been spot on. So when it was at 15.5 ppm this morning I did the math to bring it up to 18ppm. Which was I believe 43 ounces liquid chlorine. I go and check about 2 hours after adding and I'm at 19.5 ppm FC? What gives? How is it off by that much? Also, I had a green nasty pool last year and my SLAM process took a little over a week, but it went flawless. This year I didn't turn green and I'm eating through 4ppm overnight? Something isn't right.

Again, scrubbed walls. Dolphin cleaning floor. No ladder in pool. I don't have any lights, etc. Just not making sense.

Any thoughts from the veterans?

Btw... I had a fresh water top of last Tuesday. So I've been at this SLAM almost one week.

 

[Texas Splash]

A few things to consider:
- How old are your reagents?
- Pump is on 24/7 to keep water mix correct?
- Are the chlorine bottles of the same age? Did you check the Julian dates?
- In the APP, are you careful to select the correct bleach %?

 

[Mavven]

A few things to consider:
- How old are your reagents?
- Pump is on 24/7 to keep water mix correct?
- Are the chlorine bottles of the same age? Did you check the Julian dates?
- In the APP, are you careful to select the correct bleach %?

Reagents are brand new from last year, with a late 2023 expiration date.

Yes, pump running 24/7 on low speed. Last year I ran it on high speed and my electric bill was nuts. I run it on high for 1 hour after I pour chlorine in, then switch to low speed.

Chlorine is brand new from ocean state job lot, here on the east coast. Chlorine is perfect dark yellow. I compared it to 3 gallons I had from last year. The ones from last year are almost clear, as they have lost there effectiveness.

In the app I'm putting in 12.5% which is stated on the bottles.

What do you mean by Julian dates? Are you referring to the picture I attached?

 

[Texas Splash]

What do you mean by Julian dates?

On chlorine bottles you should see a number. It may look something like 23-156 which means this is the 156th day of 2023. You'd be surprised how many stores sell old chlorine with 2022 dates still on them. Even some from early 2023 "030" day (30 Jan).

 

[MITBeta]

 

[Mavven]

View attachment 500464

Okay, so this would mean it's from 2023 and from May, correct?

 

[Texas Splash]

Okay, so this would mean it's from 2023 and from May, correct?

Yes, so still should be fresh as long as it wasn't stored outside in the heat somewhere.

 

[Mavven]

Yes, so still should be fresh as long as it wasn't stored outside in the heat somewhere.

Nope, was put in my garage for storage. Would never leave chlorine outside. Thanks for the replies, but I'm still baffled at what's going on?

 

[MITBeta]

The titration testing is going to be +/- 0.5ppm. If you were a little low on the 15.5 test and a little high on the 19.5 that would account for it. I wouldn't lose much sleep over being off by a bit.

 

[pktaske]

The titration testing is going to be +/- 0.5ppm. If you were a little low on the 15.5 test and a little high on the 19.5 that would account for it. I wouldn't lose much sleep over being off by a bit.

Exactly. Unless you work in an inorganics testing lab, you're going to be off by a bit.