Struggle to get FC to MA level and maintain

[TCW515]

Greetings!

I have had areas of what appears to be mustard algae on the north and south walls of my pool for a while. Brushing and vacuuming seemed to make no difference, so I decided to do a SLAM and then go to MA level after completing that.

I bought a TF-Pro test kit, made recommended adjustments per PoolMath, then got the PH to 7.2 before starting. I took the pool lights out and placed them on towels on the deck and brushed the niches. The SLAM took about 6 days with a short interruption from the “almost” tropical storm that dumped 9 inches of rain on us. Yesterday morning we passed the OCLT, had 0 CC and clear water (it was clear when started, too). For the most part getting and keeping FC levels seemed straightforward and expected.

I started adding the amount of LC recommended by PoolMath to get to the mustard algae level yesterday and it took most of the day of testing and adding more and more before it reached the level I needed it to be. I have read that algae and other contaminates in the water can quickly use up the FC during a normal SLAM and although I had to keep adding chlorine to maintain the shock level I didn’t have trouble getting to the level initially. If you look at my PoolMath logs, you can see that I’ve had trouble getting to and maintaining the mustard algae level. My question is: is that typical? It made me wonder if the jugs of LC I just got refilled on Friday from the pool store were bottom of the tank or somehow comprised. Should I get more LC and continue to an extra day to see if I can maintain the correct level for MA?

 

[mgtfp]

I don't think your numbers look too unusual. At MA-SLAM level, you have a higher percentage of chlorine that is not protected from UV by CYA. That's why the MA protocol says to first do a regular SLAM followed by a burst to MA-SLAM level. It would cost a lot of chlorine to maintain MA-SLAM level in Florida sun.

 

[mgtfp]

I'd recommend to go down to the MA-target level after maintaining MA-SLAM level for 24h, and maintain that elevated target level for a week or two, and then see how you're going.

EDIT:
To be more precise, you shouldn't get below the MA-target (which is actually called "MA min" in chem geeks chart), so aim a bit higher.

 

[TCW515]

Thanks for your reply. Based on my numbers, do you think the FC level has been high enough for long enough to kill the MA despite the level not being maintained throughout the whole 24 hours? I could keep the pool at regular SLAM level without much fuss for another week or so, but you are correct about the difficulty of maintaining the higher MA level in the Florida sun. I hadn’t thought about the fact that the CYA would lose its protective properties over the corresponding FC level. Could that be why my numbers finally climbed yesterday as the sun got lower and this afternoon when it became cloudy?

 

[mgtfp]

Yes, less sun will make it a lot easier to maintain high FC. What's the time now in Florida, should be early evening, right? Maybe go up to MA level after sunset and give it another night. Much easier to maintain without sun. And then maintain the MA min level for a while.

Some people with recurring MA problems just settle on the elevated target level for good.

 

[TCW515]

Yes, it is 7:57 pm and cloudy right now. I will add more LC and let it work overnight and then let it come back down to the minimum for MA. As of now with a CYA of 30 that will be 4.6. I’ve gone through nearly 5 gallons of LC since yesterday morning trying to maintain 18.2, so 4.6 will be a breeze by comparison.

I would like to add a SWG before long, so I will have to raise my CYA and that number will go up, but I’ll figure that out when the time comes.
Thanks again for your help!

 

[IceShadow]

As a heads-up, you can use a 10ml sample and one scoop of powder, and each drop added is 0.5ppm FC. Will save reagents and is precise enough for our needs.

 

[TCW515]

As a heads-up, you can use a 10ml sample and one scoop of powder, and each drop added is 0.5ppm FC. Will save reagents and is precise enough for our needs.

Thank you…but now I have a new question. Do different Taylor kits have different reagent concentrations or directions? The laminated instruction card that came in my TF-Pro kit say to fill the “Chlorine Only” cylinder to 10 ml, add one scoop of powder (exact amount is not important),mix, add one drop of solution until it turns clear and that each drop equals 0.5ppm FC. I have see a few post that mention two scoops and that more is better than less when measuring higher FC level, so I have been using pretty heaping scoops during my SLAM, but using only one level scoop would only save me a bit of DPD powder. It’s the R-0871 solution that I have used in abundance. Or am I missing something?

 

[IceShadow]

If there is any undissolved powder in the water then you have enough. I find one heaping scoop to be plenty for the 10ml test.