Hello from Maryland!

[eagle47]

I'm a long-time (30-year) pool owner who now, thanks to the TFP forums and Pool School, know that I've done just about everything wrong (LPS, chlorine tablets, $$$ spent on unnecessary chemicals, etc.) but am trying to get smarter and up-to-speed. I'm now doing my own testing and using liquid chlorine with mostly successful results. One problem remains...

I cannot maintain a stable chlorine level over a sustained period of time, with readings sometimes fluctuating wildly between tests. For example, 3 days ago pool looked great and reading were nominal (FC/CC = 1/1 (yes, I know it's low), pH = 7.8, CYA = 50). Then yesterday I discovered multiple greeen algae blooms and FC had dropped to zero! I shocked last night and this morning FC is still at 1, but CC has skyrocketed to 3. Obviously something is consuming the chlorine, but TA is at 100 so I assume stabilizer is OK.

Any ideas?

 

[Texas Splash]

Hello and welcome to TFP! Not to worry, I think most of us learned pool chemistry the hard way. Your situation seems to be algae-related, and best suited for a SLAM via Pool School - SLAM - Shock Level And Maintain. You increased FC slightly for a short time, which indicates the increased CC level, but you haven't been able to maintain and completely kill the algae. Please follow the SLAM page and you should get back on-track. Great to have you with us!

 

[BoDarville]

Welcome to TFP!

Texas Splash has set you straight on the recommended course of action. Just keep in mind that the most important part of the SLAM is the M for Maintain - as in Maintaining the FC level as close to the target according to your pool's CYA throughout the entire SLAM process (see [FC/CYA][/FC/CYA]). A lot of new members frequently overlook this detail.

 

[eagle47]

Thanks for your recommendation which I have begun to implement. But, well, it's not going as expected...

With all the pre-conditons being met, I began the SLAM by adding the prescribed amount (4 gal) of liquid chlorine (10%) to the pool last night. My 30-min readings indicated no change in FC, so I assumed it would take the usual 8-10 hours to completely turn over the water and see a difference in the FC level. So this morning I took another reading only to see that the FC level has DROPPED TO ZERO. How can this be?

Here's a summary of SLAM reading to date:
Day 1/PM
(T=0) FC = 0.5/CC=1.5
Added 4 gal. chlorine
(T+30) FC = 0.5/CC=1.5

Day 2/AM
FC = 0.0/CC = 0.5

Is this typical or have I made some rookie mistake? Are there other (hidden) factors that would cause the FC level to go the wrong way AFTER adding chlorine?

Very frustrating.

 

[Texas Splash]

Eagle, when conducting a SLAM, we don't spike it at night and leave it alone. Your comment about no change in FC for 30 min is alarming sure, but we don't stop adding bleach until you reach your SLAM level and then keep it there. That's the key. Also, we don't wait for "pool turnover", simply allow at least 30 minutes for the pump to mix the chemicals and that's good enough.

Now, because your FC has been allowed to drop to zero, there's always the potential for ammonia to try and creep-in on you. SO here's what I would like for you to do:
1. Begin a SLAM and dose FC up to SLAM level. Do not add additional CYA at this point.
2. Retest FC at 10-minute intervals. (VERY important!)
a. If FC loss is greater than 50%, add FC to bring back up to SLAM level and continue retesting FC @ 10-minute intervals.
b. IF FC loss is 50% or less, add FC to bring back up to SLAM level. Go to Step 3.
3. If CYA is below 30 ppm, add enough CYA to bring level up to 30 ppm.
4. Continue SLAM as directed in the SLAM article until the SLAM Criteria of Done are met. Test as directed in the SLAM article - no longer need to test FC at 10 minute increments at this point.

Follow these instructions and that should help get you back on-track.

 

[eagle47]

Thanks Texas for the quick response. My apologies - I obviously misinterpreted the SLAM procedure steps.:joker:

So, back to the warehouse for more chlorine. Guess how I'll be spending my Labor Day weekend?

 

[Argosy]

Ah, Maryland! The birthplace of my Taylor K-2006

Once you fix your algae bloom and get back to clear water, do not allow for your FC to drop below 1.0. Even better, sock the pool if it drops to 2.0.

One time, FC in my indoor pool dropped below 0.5 (by-law minimum for unstabilized pools) and the next day, I had a mild algae bloom in a form of cloudy water. Had to SLAM it for 3 days at FC=8.0 to get back on the right track. With an outdoor pool those things happen much faster!

Good luck and welcome to TFP