Question about raising Chlorine

[nparman]

New pool owner here, and this site has been a huge help getting me accustomed to pool maintenance. Thank you!

Since inheriting the pool six months ago, my FC and TC have been reading 0. All other levels have maintained the desired range (see below for most recent results) with the exception of CYA, which had been about 112. Up until this point, I had been assuming my difficulty in holding chlorine was a result of the high CYA, so per Leslie's pool recommendation, I was able to lower my CYA to 50 using their bioactive product. Since then (about 3 weeks ago), my CYA has stayed around 50, and I've been shocking the pool using liquid chlorine, but have still not been able to register any chlorine readings on my home test kit (taylor k-2006).

Per the CYA/chlorine shock chart, I've been shocking with 4 gallons of 12.5% sodium hypochlorite to reach a shock level of 20ppm. I also have a chlorine float with 3" pucks that I've kept in pool once CYA was lowered. The pool has been crystal clear this entire time with no algae or cloudiness.

My questions:
1) Should I be shocking with the full 4 gallons every night until I see a reading? I've been doing it about every 2-3 days, which seems excessive, but I'm wondering if I'm actually just not doing it enough.
2) I've only been testing chlorine levels the morning after a shock. Should I be testing sooner to see if the levels are ever raised? Is it safe to test the water immediately after shocking?
3) Any other ideas as to why I'm struggling to get any reading?

Thank you!

Most recent test results, 1 day after shock:
FC: 0ppm
TC: 0ppm
CH: 370
CYA: 50
TA: 70
pH: 7.4
TDS: 1050

 

[Texas Splash]

Hello and welcome to the forum! I'll get right to your questions:

1) Should I be shocking with the full 4 gallons every night until I see a reading? I've been doing it about every 2-3 days, which seems excessive, but I'm wondering if I'm actually just not doing it enough.

No, you should be following the TFP SLAM Process process. Test and add bleach as much as needed to maintain the SLAM level.

2) I've only been testing chlorine levels the morning after a shock. Should I be testing sooner to see if the levels are ever raised? Is it safe to test the water immediately after shocking?

You should be testing your water at home with either a TF-100 or Taylor K-2006C test kit as frequent as needed to "maintain" that FC SLAM/Shock level. You maintain until you pass all 3 SLAM criteria.

3) Any other ideas as to why I'm struggling to get any reading?

At this point, simply test with a proper test kit and follow the SLAM Process page. Let the chlorine do the work, but it has to be accurate. The pool store testing is often flawed and will steer you wrong.

Nice to have you with us.

 

[nparman]

Test and add bleach as much as needed to maintain the SLAM level.

Thank you for the response! One more clarifying question: If I'm adding chlorine to shock level (20 ppm in my case), and I need to maintain this level until overnight loss is no more than 1ppm, then how do I get the level back down to target range once SLAM is complete? If at that point there's only 1ppm lost per day, does that mean it won't get back to 7-8ppm 12-13 days after stopping? I'm assuming it's not safe to swim while at the SLAM level?

 

[proavia]

Normal daytime FC loss is 2-4 ppm per day. The UV rays of the sun burn off more FC in the daytime - OCLT is done at night so the sun isn't a factor in determining overnight FC loss. You just let the FC drift down to your target range. It is safe to swim as long as FC is between minimum and SLAM level for your CYA - based on the [FC/CYA][/FC/CYA] - and you can clearly see the bottom of the pool in the deep end.

 

[Texas Splash]

In most cases, the Overnight Chlorine Loss Test is reserved towards the end of the SLAM. Not always, but often times. But once the SLAM is complete by passing all of those 3 criteria, then you simply stopping adding bleach. The sun will take that additional chlorine fairly quickly bringing you back down to the daily recommended FC range noted on that chart. Also, the water is still safe to be in as long as you do not go over your SLAM level. Many people go in the water to brush, clean, or simply cool off. It's okay as in your case you don't go over an FC of 20.

 

[mknauss]

It is safe to swim when your FC is above minimum and at or below SLAM level based on your CYA. You also need to be able to see the bottom of the deep end.

Your FC will drop during the daylight hours. At SLAM level you will lose 15-20% of your FC during the day due to the UV from the sun. The FC will be at your target level in a couple days. Then, you will need to add chlorine DAILY to make up for the FC lost the last 24 hours without ever letting your FC fall below your target level.

Take care.

 

[nparman]

Awesome, thank you all so much for the responses!

 

[JoeSelf]

1PPM overnight after the pool is totally clear. You can swin at SLAM or below. The farther above TARGET level the faster the sun eats it up. Usual daytime losses are 2-4 PPM with no bathers depending on sun levels & CYA LEVEL.

 

[sleepysdad]

I have a hard time believing that you are pouring 4 gallons of bleach into the pool and not getting an FC or CC reading. If your kit reagents are old - please reorder. This is one time I would tell you to take a sample to the pool store to double check. In my experience the chlorine you are pouring in should register as either FC or CC (if being consumed) shortly after adding.