Calcium Hardness & Fading Endpoint

[TikiTime]

I am still learning how to use the TF-100 kit. I am running in to a problem with the Calcium Hardness test. My results are all over the place...and I think I have endpoint fading as my sample turns purple for a few drops before it turns blue. Suggestions? Can I do a 10ml test adding R-0012 before adding any R-0010 or R-0011L....or do I need to do the 25ml test for this version? Just looking to conserve reagents.

Pretty sure the calcium is high as I have quite a bit of white film in filter that flakes off. above water line smooth, below is rough. fiberglass pool.

Pool is not directly under roof line, but close to it. Seems like I have asphalt shingle particles (even through pool cage) on a weekly basis. Not sure if asphalt shingles contain metal particles, but I am guessing yes as I have flea sized rust spots in the area where the roof particles are.

I am still using pool service for a few more weeks. They don't come for another 4 days. I have 2 gallons of pool store chlorine...not sure of strength...roughly how much should I add to bump up chlorine so I don't have an algae problem the next few days. Florida temps are 75ish right now.

Here are results for today

FC = 1
CC = 0
TC = 1.0
CH = 300 with 10ml test
CH = 260 with 25ml test
TA = 90
CYA = 40
Ph = 8.0​

My first attempt at TF-100 3 days ago:

FC = 2
CC = 0.5
TC = 2.5
CH = 425
TA = 100
CYA = 40
Ph = 8.0​

 

[JamesW]

You can do 10 ml with a few drops of 12 first. Fading endpoint is most likely caused by copper.

Also, you need to get the pH down.

 

[Patrick_B]

Welcome to the forum TikiTime!

Congratulations on taking over the pool yourself too.

From a testing standpoint your CH test doesn't look bad at all. You will always lose accuracy with a smaller sample size, so don't worry with that.

Don't change the order of reagent addition, follow the instructions always. Something you can try is adding a few extra drops of R-0011L. This will make your end point more vivid and visible. What you describe is perfectly normal on the color transition. Purple-ish to Blue. At your level of CH, I would use the 25 mil test though. It really isn't high, but with a consistent pH of 8.0, it could explain some scaling. You really want to get that pH down to a better number like 7.4-7.5.

As for the shingle particles, I haven't the faintest, but it could be iron or something causing similar stains. Try placing a vitamin C tablet on them for several seconds to see if they fade.

At 40 Cya, you want to target 5.0 PPM FC. Are you sure the Liquid Cl from the store doesn't give strength? It should. If not, assume it is 10%, then base the dose on that using Pool Math, and work it from there.

 

[Richard320]

There's no substitute for a speedstir on that CH test. I use a 10 ml sample, to save time and reagent. Instructions are here, in post #7. Except I use 5 drops of R-0011L instead of 3 so the color is deeper. It won't change the results any if you add a little R-0012 first, as the instructions indicate, for fading endpoint. And then expect it to take a long time. I can't imagine how long it would take manually. But with a speedstir, it will start to turn colors and that's when you need to slow down, and maybe even let it run a full cycle on each drop. Many times it will go from purple to blue without adding anymore drops, just another minute of spinning. I would estimate a minute on the speedstir is better than two minutes or wrist action.

 

[TikiTime]

I retested with a few drops of R-0012 at the beginning and slowed down overall. My 3rd test was 275. I have decided to order the SpeedStir...I think it will really help on the CH test.

Also bumped up my FC to 7.0, was aiming for 5 but overshot a little. I think my pool may be less than the 16k I was estimating. Also dropped Ph down to 7.6...need to bring it down a little bit more, but I am starting to get the hang of it.

Thanks for your help!

 

[JamesW]

You're doing well. I think that you have a pretty good understanding of what to do.

 

[Patrick_B]

I'd say so too. Just keep after it and you'll have a really good feel for what to add in no time. Good job!

Once you use the speed stir, you'll never look back except to wonder why you didn't do it sooner.