Reading Shock-Level FC Numbers

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ssmith1627

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Jun 2, 2008
83
Knoxville, TN
Guys, I posted this in someone else's thread but thought I'd post it again here instead of hijacking their conversation.

I have a decent test kit from a local pool place. It'll test FC, TC, TA, Ph, CYA and CH. But the chlorine readings don't go any higher than 5.0.

When I'm shocking the pool and want to keep the levels really high, how can I tell where I am before it falls below 5 again ? Do I double the sample of water, add the reagents, pour some back into the comparator and then double the result I get ? Or even go to 4 tmies as much and quadrupling the result ? Just trying to think of a way to make that work.

Any ideas would be appreciated. Would like to know the FC numbers as well as TC/CC without having to get my water tested by those guys.

Just bought a house and I'm trying to bring a pool back to life from green swamp status. A day of BBB and high chlorine levels with bleach and I'm no longer green. Have a blue cloudy pool now and I'm trying to see what I need to do next.

Many thanks,
Steve

24' Round A/G, 13500 gal., 1HP Pump, Sand Filter
 

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Hi, Steve,

The chlorine test that will test 50+ppm (and with great accuracy) is the FAS/DPD test. It's found in the kit's recommended most often here (TF-100, K-2006).

Taylor and I both sell it as an individual test. They put their's in a plastic kit box and, generally, is a little more expensive than mine for $23.00...which only comes with the chemistry and hardware necessary...no kit box. The chemistry and test method is identical.

It is incredibly troublesome to clear a green pool without this test.
 
Keep the shock up, but that's hard to know if you are keeping it up long enough to kill the algea if you don't have the proper test, as Dave described.

If you can't invest in a proper test then you will need to take a sample to "those guys" daily to be sure....
 
"those guys" certainly wasn't mean in a deragatory way. Just hate to have someone else test it when I can do it myself, especially with the frequency at which I need it tested.

I need a lot more bleach apparently. I put in a great deal yesterday but it dropped to 1 or below overnight. That really amazes me. I'll get the test kit ordered so I know more of where I stand. In the mean time, I'll try to keep the levels high to kill off everything in there. It's still very much blue but it's cloudy. And with the chlorine levels refusing to stay up, I guess there's a lot of work yet to be done.

My TA yesterday was 70 and my CYA was 60. My Ph was 6.2 but I brought it up to 7.2 yesterday. So everything seems ok except that I'm fighting to keep the chlorine levels high.

Steve
 
ssmith1627 said:
"those guys" certainly wasn't mean in a deragatory way. Just hate to have someone else test it when I can do it myself, especially with the frequency at which I need it tested.

I need a lot more bleach apparently. I put in a great deal yesterday but it dropped to 1 or below overnight. That really amazes me. I'll get the test kit ordered so I know more of where I stand. In the mean time, I'll try to keep the levels high to kill off everything in there. It's still very much blue but it's cloudy. And with the chlorine levels refusing to stay up, I guess there's a lot of work yet to be done.

My TA yesterday was 70 and my CYA was 60. My Ph was 6.2 but I brought it up to 7.2 yesterday. So everything seems ok except that I'm fighting to keep the chlorine levels high.

Steve
Click to expand...

Oh, I meant it in a deragatory way... :twisted:

With the exception of the rare helpful ones that is... like Waterbear and others I'm sure. I've had helpful pool store employees on occasion.

Sounds like you are getting a handle on it, it is amazing to see it drop so quicky, means it's working!

Good luck....hang in there.
 
That's exactly what I figured. If it's getting used up so quickly, it's for a reason. My CYA level is normal so it's not just the sunlight zapping it. Someone else told me if my metals levels are high the chlorine will combine with those instead of doing the work I want it to do. So that's one test I do want to get done.

I've had mixed results with the three pool places I've gone in. Yesterday, very helpful. Tested, talked and walked. The other two -- I don't know -- almost made you feel like you were bothering them. Emailing them with the addresses on their websites seems useless too. I started out trying to have someone come out to help me clean this up since I've never done this before. No returned calls, no interest at all in helping me. I have a dirty pool and money and want help. I've never seen a situation where people didn't want to take your money before ! But now I'm learning with the help of you guys and your website and another friend. I'm confident I can win the battle.

Thanks for the guidance and feedback.

Steve
 
duraleigh said:
Hi, Steve,

The chlorine test that will test 50+ppm (and with great accuracy) is the FAS/DPD test. It's found in the kit's recommended most often here (TF-100, K-2006).

Taylor and I both sell it as an individual test. They put their's in a plastic kit box and, generally, is a little more expensive than mine for $23.00...which only comes with the chemistry and hardware necessary...no kit box. The chemistry and test method is identical.

It is incredibly troublesome to clear a green pool without this test.
Click to expand...

The test kit I just bought has the DPD test. But the comparator only reads up to 5.0. Is it something I'm just not understanding here or is the test read in a different way in the TF-100 kit ?

I feel like I have a good test kit for everything except these really high chlorine levels. If nothing else, can I just buy that part ?

Steve
 
There's DPD, which uses color matching (usually you add a tablet of DPD powder, and the intensity of the pink tells you how much free chlorine you have). Then there's FAS-DPD. In this case, you add the DPD reagent to the water, and it turns pink because there is free chlorine. Then you add FAS (ferrous ammonium sulfate) drop by drop until the water is clear. The number of drops is multiplied by a factor (varies from test kit to test kit) to determine actual free chlorine levels. The FAS-DPD has a much greater range of testing that it can do than the OTO or the DPD w/o FAS.
 
Steve wrote:
I feel like I have a good test kit for everything except these really high chlorine levels. If nothing else, can I just buy that part ?
Click to expand...


Duraleigh wrote:
Taylor and I both sell it as an individual test. They put their's in a plastic kit box and, generally, is a little more expensive than mine for $23.00...which only comes with the chemistry and hardware necessary...no kit box. The chemistry and test method is identical.
Click to expand...
 

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I'm sold. Going to place the order now. Thank you.

I see you add the powder to turn it pink. Then you add one drop at a time and count. Does the solution change back to clear when you find the right number ? My other TA test was similar to that so just curious.

Thanks again.

Steve
 
Matt said:
There's DPD, which uses color matching (usually you add a tablet of DPD powder, and the intensity of the pink tells you how much free chlorine you have).
Click to expand...
There are also DPD tests that use all liquid reagents. Both Taylor and LaMotte have them.
 
ssmith1627 said:
I'm sold. Going to place the order now. Thank you.

I see you add the powder to turn it pink. Then you add one drop at a time and count. Does the solution change back to clear when you find the right number ? My other TA test was similar to that so just curious.

Thanks again.

Steve
Click to expand...
Exactly! The Taylor Technoligies website has an excellent article that shows the color change.
 
I really like the FAS-DPD from Taylor. Mine uses a powdered reagent for the DPD and a liquid titrant (FAS). It's pretty obvious when it turns clear, so it really does allow you to more precisely measure levels of chlorine. Also, with the Taylor (or in theory with any), you can use different amounts of pool water, which gives you a different level of precision (0.2 vs 0.5 are the ones included, but you can get creative and use any dilution factor you want... but you can follow the directions very easily and use either of those two included ratios).
 
I just want something to show me where it is so I can watch it fall during the day -- at least during this critical part of trying to beat whatever is in my pool. I feel like with the test kit I have now that I just know it's above 5.....and then I get up the next morning (like today) and it's plummeted to near zero. I want to see it at 15 and then 12 and 9 and know it's coming down before it's at rock bottom.

Ordered the individual test kit today so hopefully I'll have that within a few days.

I don't think it'll be an issue once the water is clear and I'm just trying to keep a normal level of chlorine in there.

Steve
 
Got the test kit now so I'm working to keep the FC numbers high. I think my mistake before was boosting it TO shock level and letting it drift back down before I added more when I got up in the morning or when I got home from work. My idea now is to boost it higher so that it stays at shock level or above. I pray that with that going and the filter running 24/7, my pool will finally clear. The water is incredibly blue and beautiful. But I can only see down to the 2nd step and vaguely the 3rd. No hint of the liner / bottom. I want clear water !

Steve
 
ssmith1627 said:
Got the test kit now so I'm working to keep the FC numbers high. I think my mistake before was boosting it TO shock level and letting it drift back down before I added more when I got up in the morning or when I got home from work. My idea now is to boost it higher so that it stays at shock level or above. I pray that with that going and the filter running 24/7, my pool will finally clear. The water is incredibly blue and beautiful. But I can only see down to the 2nd step and vaguely the 3rd. No hint of the liner / bottom. I want clear water !

Steve
Click to expand...

Yes, letting it drift back down doesn't help. Plus you were guessing about how much was in there. Figure out your target, dose to that point, and keep it there till the number holds over night. And the only way to do that is with the chlorine test that uses the powder.

Youre almost there!!! :-D
 
It makes sense -- keep it at a higher target for when it has to drift down so it doesn't go below shock level. That part just didn't dawn on me until yesterday.

But like you said, I have an accurate test now and I know where to keep the level. And I have a lot of bleach handy.

Steve
 
Many thanks. That does help. Makes me feel good about the concept of all this I have in my head. I posted a little yesterday in other forums where people didn't seem to be getting the FC up nearly high enough. Same thing -- if your chlorine is below shock level, it seems like you'd only be killing off as much algae as grows each day. So you're making no real progress. If that's adding 2 gallons a day of chlorine then you'll be adding 2 gallons every day from here on out with no result. You have to add 6 gallons and keep it up there to kill more than is growing and put an end to it altogether so that after that you can add 1/4 of a gallon a day.

Just my thinking.

Thanks for pointing me to some more information.

Steve
 

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