Need Guidance Post Cobalt Cure Treatment

[largeal]

Long time lurker and now finally my first post...

Okay...so here's where I'm at. Had some cobalt staining in my fiberglass pool so I thought i would give United Chemical's 'Cobalt Cure' a shot. Turned off the pumps, added the appropriate amount of muriatic acid and cobalt cure, brushed the pool sides and let it sit overnight. After 24 hours a lot of the spots had started to disappear. Instructions stated total alkalinity must get to zero and if not, add more acid. So I used my TF-100 test kit for the TA test. After adding the R-0008 the solution immediately went red. I took this indication as a 0-Level alkalinity since the R-0009 wasn't needed to turn the solution red and count the drops needed.

So at this point, since my cobalt staining was severe, I decided to supplement the recommended portions by adding more cobalt cure, muriatic acid, brush the pool walls again and check the results the next day (probably wasn't needed).

After 48 hours all my black cobalt staining was removed. HeeHaw!!! Time to get my chemistry right again as heavy rain was expected in the next few days. Again following the instructions the pH needed to get back to 7.8. So, got out the test kit and proceeded to do a Chlorine and pH test. Whoa...the chlorine side solution color was clear and the pH solution was yellow...like chlorine level 3 yellow. This is where I should have asked TFP for help but noooooooooooooo...I got this. But truth be known, I didn't and still don't. Still getting the same results on the chlorine and pH level tests after adding liquid bleach and borax using Pool Math as a guide (even though now I'm not sure those were the correct steps to take). I also performed a chlorine drop test tonight..after adding the R-0870 powder it still looks almost clear to maybe the lightest shade of pink possible. The pool water is still crystal clear after starting this whole process 5days ago (Thurs.) without the pumps running.

I really don't want to screw this up any more than I probably already have...so if someone could please help out this chemically challenged non-pool expert with some guidance I certainly would appreciate it!

Al

CL=???
pH=???
TA=0
Water Temp=70*
Salt Level=3400ppm

 

[mknauss]

Re: Need Guidance Post "Cobalt Cure" Treatment

Borax will raise pH but not effect TA much. Soda Ash will effect both.

So in your pool, PoolMath shows if you add 32 oz of soda ash it will raise pH 0.6 and TA 20. Are both still below reading on your test? If so, I would add the 32 oz and see if it effects your test. Then start using PoolMath and switch to borax if TA is above 50 and you need to raise pH or baking soda if pH is above 7.2 and you need to raise TA.

Hope that helps. Go in little steps. Be careful with the soda ash.

Take care.

- - - Updated - - -

Also - do a FAS-DPD test for chlorine. It might be very high (not sure how much bleach you added) and bleaching out the color in the block test.

 

[largeal]

I'm off to the store this morning to get both some A&M soda and 20 Mule Borax. I will start with adding the soda ash as you suggested and check pH and TA again. Then top off with soda ash or borax as needed.

I did the FAS-DPD test last night using the FT-100 kit directions and from the indications thought that the FC level was at zero. I printed out the TFP FAS-DPD chlorine test instructions and will attempt the test again as the steps are much more detailed.

Will report back of my progress later today...thank you for taking the time to keep me steered in the right direction.

Al

 

[ka8yiu]

Did you check your CC’s when you did the chlorine test?

After my stain treatment (Jacks Magic) my chlorine showed up as CC due to the sequestriant in the water. That took several weeks to clear up. I was tempted to add more chlorine to burn the CC readings off, but it runs the risk of bringing the stains back.

You may just have to ride out the no CL reading and use the CC readings and wait for it to switch back to correct CL readings. Adjusting the ph may be tricky as you don’t know the correct chlorine level right now.

Again, this is just from my experience with my fiberglass treatment.

 

[largeal]

Did you check your CC’s when you did the chlorine test?

Actually, I didn't. When my sample didn't turn pink (well, as I stated in OP, not clear but maybe the slightest shade of pink possible?) I didn't continue on with the test. And at this point I'm exactly where you were...tempted to add more chlorine but afraid the staining will come back. The pool water has remained crystal clear and the pool walls look like new.

I will again run the FAS-DPD chlorine test and complete all the steps and see what comes up.

I really appreciate your input. Al

 

[duraleigh]

First, get your pH into the mid 7's....repeating doses as needed (about 30 min apart or so). Use 20 mule team borax. Once pH is measurable, you can start on FC.

 

[largeal]

First, get your pH into the mid 7's....repeating doses as needed (about 30 min apart or so). Use 20 mule team borax. Once pH is measurable, you can start on FC.

As of right now Dave...that is the plan and a better FAS-DPD test to hopefully see where I'm at with the chlorine levels.

Thank-you...Al

 

[Swampwoman]

I believe cobalt cure is Oxalic acid, in which case, you should keep trying (gently) to raise the FC. Just like the ascorbic acid treatment, the Oxalic will keep eating FC until you've oxidized it.

 

[largeal]

I believe cobalt cure is Oxalic acid

Yes it is...which would explain my chlorine issues. Just got back from Wally World with some 20 Mule and A&H. Will start with the borax and see if I can get my pH back up.

Thanks, Al