Preparing to SLAM... very low CYA, use Diclhorine?

rodpp

Member
Apr 10, 2019
10
Brazil
Hi folks,

My Taylor K-2006C Kit arrive yesterday (unfortunately the TF-100 cannot be send to Brazil), and I did a full test:

FC: 1.2
CC: 0.6*
pH: 7.4
TA: 90
CH: 375
CYA: 0**
t: 28ºC
CSI: -0.03

(I added 70g of Dichlor aiming rise the FC 3ppm.)

* I'm using a magnetic stirrer, the solution color turned to "no color" and after around 30 seconds it returned to light pink. Added more reagent and it turned "no color" again, 30s after and it returned to light pink, and so on. I did this until CC=1.2, after that it turned light ping again and I gave up. The above value of CC=0.6 was when the first time it turned to "no color".

** I filled almost the entire tube with the solution and the black dot was still barely visible. It only complete disapeared when the test tube was 100% full.

As I have CC above 0.5, the SLAM is necessary. What should I do:

1- Add CYA before SLAM to reach at least 30ppm, and start the SLAM after that using 65% Cal-Hypo (and undesirably raising CH); or
2- Use Dichlor to SLAM aiming two objectives: Lower the CC and rise the CYA.

I already have:
- 10Kg of Dichlor
- 10Kg of 65% Cal-Hypo

As my pool is only 13.000 liters, I plan to use exclusively these two products for a long time.

Thanks in advance!

Regards,
Rodrigo.
 

Richard320

TFP Expert
LifeTime Supporter
Jan 6, 2010
23,923
San Dimas, CA (LA County)
The test solution turning pink again after sitting is normal. You did right by using the first time it went clear as the measurement.

A couple things: 1) use only 10 ml water when testing FC & CC. It's precise enough and it will save a lot of reagent, which is an important consideration for you. Multiply by .5 instead of .2.
2) Your Calcium is already heading to the high end. 10kg of 65% Cal-hypo will raise CH by another 350 in your 13000 liter pool!
3) 10 kg of dichlor will raise CYA by 388 in your pool!

Neither one of those is sustainable for very long. You'll end up with sandpaper growing on the walls, or an algae bloom, unless you do a lot of water replacement. They don't sell bleach in Brazil?

If you insist on using your powdered chlorine, make yourself familiar with Effects Of Adding Chemicals at the bottom of PoolMath Upper right corner will let you switch to metric. Use the dichlor until you get to 30 CYA then switch to Cal-hypo until you finish the SLAM. Then I suppose you can use the dichlor again until CYA is 50ish and switch back to Cal-hypo. You'll need to pay attention to the CSI and manipulate pH and TA to keep it in range as the CH climbs.
 

rodpp

Member
Apr 10, 2019
10
Brazil
Yes, I have access to plain bleach. But the concentration is very low, the max I found was 2.5%. Maybe I can find it more concentrated in specialized chemical stores. As I already have the poudered chlorines, I did not search much.

Regarding the tests, I'll use 10ml water to save reagents, thanks!

So I'll start the SLAM proccess in the following way, as sugested:

1- rise the FC above 12 (shock level for CYA = 30) using Dichlor (around 250 grams);
2- maintain the FC >12 using Dichlor until CYA reach 30 (after around 800g of total Dichlor added);
3- switch to 65% Cal-Hypo to maintain the FC > 12 until finish the SLAM process.

As my pool is very small, water replacement is not a big problem. Backwash cleaning the filter and vacum the entire pool to drain once in a while should be enough to lower the CYA and CH levels.