Chem Geek or Mbar - are you there? Iron test question.

I have a quick silly question, that I couldn't find the answer to when searching the Forum.

Does sequestered iron (which if I understood Chem Geek correctly from another post, are iron ions) show up on a pool-store iron test?

I'm Dianna (labdi01) - the one with the homemade quilt-batting filter ("New Pool Owner Manually Removing Iron"), that we ran for 72 hours after shocking turned my pool opaque brown and it cleared it up beautifully.

I went to pool store today to have water tested and they told me I have 5 ppm of iron, when my pool is perfectly clear, numbers mostly where they should be.

CL - 3
FC - 3
pH - 7.2
Alk - 130
CA - 50 (told me I had to bring it up w/ 10 lbs of Balance 300 - I ignored him)
CYA - 100 (claims that's fine - I understood this to be a problem from the Forum)
Iron - 5

I came home after this visit and shocked w/ 2 lbs of HTH Super Shock and Swim, with the intent of knocking any sequestered ions out in the open to be filtered, and my pool remains clear (it's only been about 10 mins after shock).

Could either or both of you shed some light on the iron result?

I'll leave the iron comments to the experts, but I will say that a FC of 3 with a CYA of 100 is not going to leave your pool clear for very long. You really need to either drain/refill half your water to get it down, or get your chlorine up to the 8-10 range, otherwise you're going to have problems keeping the algae away.

Janet

I forgot to mention what my iron levels had been...

When first opened and shocked (water turned opaque brown) iron was 3
After 6 quarts of sequestrant and several days (water was clear/green) iron was 0.5
After adding 6 gals of bleach (water was opaque brown again) we didn't test
After filtering to clear iron was 0
Attempted an ascorbic acid treatment, didn't add anything but acid and 1/2" water (with batting filter in pool and prefilter on hose) for the last 48 hours
Now it's 5

???

Thanks for your reply Janet.

After I got those numbers, I shocked with 2 lbs of HTH Super Shock and Swim, so hopefully, that brings my chlorine up beyond 8/10, no?.

Oh, sorry, I missed that the first time I read your post. That probably did bring it up beyond 8, but you're going to need to keep it there, at least 8, for as long as your CYa is that high. Not sure what the chlorine source of Super shock and Swim is, but if it's dichlor you need to stop using it because it raises CYA even further. You're probably okay for awhile if it's cal-hypo, but when your calcium numbers start getting past 200 or so you'll need to switch to bleach or liquid chlorine.

Janet

Super Shock and Swim is Cal Hypo.

Actually, they said my calcium was low - so that might actually prove beneficial!

My Taylor 2006 kit just arrived 10 mins ago! No more pool store!

So, the store told me this am that my CYA was 100. I did the Taylor test for CYA. The first time I did it - my CYA registered 40. I had some water left and tried it again. I didn't have enough to make the dot disappear, but I could still see the dot when I ran out of treated water - and that stopped at 60. I think the kid at the store did it wrong!

So, I did my chlorine - this is where I might be in trouble. My FC was 60 and my CC is 4.5 (I shocked at 10am with 2# cal hypo to scare out any metals).

Do I have a new problem on my hands because of the CC?

Try those chlorine test again. I can't imagine that your FC is actually 60 and CC is 4.5.

Also, is this a vinyl pool? (I can't remember from your other thread.) If so, you don't need calcium.

I goofed Watermom! I misread the instructions and multiplied by 3 not 0.5 (don't ask). So my CL is 15 and CC is 4.5. I read horror stories about getting this balanced (someone used over 100 gallons of bleach.

I do have a vinyl lined pool (AG 24')

I did the rest of the testing, too.

FC - 15
CC - 4.5
pH - 7.2
TA - 60
CA - 50
CYA - 50

My only concern about my numbers from the Taylor test is there were 2 incidents where the color they described was not the color I got - but adding more reagent didn't make a diff. Example - in the TA test, my color was supposed to change from green to red. I got more of a magenta. The calcium test said solution should turn blue. I had more of a indigo/purple.

With a CYA of 50 - I removed the CYA sock from the pool (this am pool store told me my CYA was 100 - but I did Taylor twice and got 40 and 50 respectively).

Quote:

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Originally Posted by labdi01

Does sequestered iron (which if I understood Chem Geek correctly from another post, are iron ions) show up on a pool-store iron test?

I came home after this visit and shocked w/ 2 lbs of HTH Super Shock and Swim, with the intent of knocking any sequestered ions out in the open to be filtered, and my pool remains clear (it's only been about 10 mins after shock).

Could either or both of you shed some light on the iron result?

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I had that same question and asked Taylor Technologies about it a while back and basically the iron test that they use and probably ones that others use test all iron that is present including that which is sequestered since the sequestering agents bind the metal ions somewhat loosely in an equilibrium so that as the free metal ions get used up in the test more are released from the sequestering agent. This is similar to how the FC tests all chlorine including that bound by CYA.

So that would explain why you still measure iron in your pool, yet it is clear. It also explains why you are not able to precipitate it because the concentration that is unbound is fairly low so would take a heck of a high pH to be able to form precipitate (i.e. the metal sequestrant is doing its job well).

Unfortunately, that means there is no easy way for you to tell your "free" metal ion level other than seeing that the water is clear and that you aren't getting any staining. The 5 ppm of iron the pool store is measuring is mostly bound to your metal sequestrant -- you must have used quite a bit of it to sequester that much iron.

The better sequestering agents are slower to get oxidized by chlorine so it isn't easy to break them down to release the iron, but that's the point of a good metal sequestrant anyway. You don't want it to break down easily because if it did then you'd have to add more much more frequently and it would also increase your daily chlorine demand.

Richard

Quote:

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Originally Posted by labdi01

My only concern about my numbers from the Taylor test is there were 2 incidents where the color they described was not the color I got - but adding more reagent didn't make a diff. Example - in the TA test, my color was supposed to change from green to red. I got more of a magenta. The calcium test said solution should turn blue. I had more of a indigo/purple.

With a CYA of 50 - I removed the CYA sock from the pool (this am pool store told me my CYA was 100 - but I did Taylor twice and got 40 and 50 respectively).

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For what it's worth, the color palette you describe for the end-point of the Total Alkalinity (TA) and Calcium Hardness (CH) tests match that of my testing.

TA test titration ends in a dark magenta (not red)

See http://gizmodo.com/assets/resources/2007/11/magenta.jpg

CH test titration ends in indigo / lavender (not blue)

(I'm not aware of any particular reason for these discrepancies and have tried performing the tests in every way recommended by Taylor and others, but the results are invariable and have been for 3 years.)

Thank you so much Polyvue!

I doubted myself more than the test.

Thanks Chem Geek!

Although that makes complete sense to me that the iron test would measure sequestered ions, what I'm not understanding (and please pardon my pool/chem ignorance) is how my iron tests went from 0.5 in the days following (6 quarts of) sequestrants. Then we shocked, turned back to brown, filtered to clear, then iron was down to 0. Then suddenly, iron went up to 5 (in 48 hrs - from 0) without adding so much as 1/2" of water. I would think for that to happen in a 13.5K gal pool, I would have seen sludge come out of the hose and I didn't, nor did I get any staining with that top-off.

That's an easy one to answer. The pool store likely screwed up one of the iron tests would be my guess. Happened with mine also

Question is - which do I believe?

My advice is to look at your pool - if it looks good, don't worry about it:) After many years of trying to find out where the metals were coming from, and how to get them out of my water, I came to the conclusion that I would deal with the stains as they come. I hate stains, and I am not a chemist like chemgeek. I just give the benefit of my experience. Now I just enjoy my pool and deal with the dreaded stains if and when they come

You're right mbar! Thank you so much for sharing your wisdom with me! It's greatly appreciated.

Right now, I have the pool at shock level to rid a high CC (and I seem to be winning). I have liner stains as well, and they're driving me crazy - because from a distance, it makes my pool look green (liner is blue and white with an alligator-skin pattern) and I feel like I worked too long and hard to get the pool in shape to be left with it looking any less than perfect. ;oP

Should I hold off on an ascorbic acid treatment after just fighting off a potential bloom and wait for the pool to be stable for a little bit?

Yes hold off. I would get the chlorine to hold steady overnight. Keep the ph low at about 7.2 - when you are finished shocking and the chlorine is holding, then add more sequestering agent. This should take care of the staining. If it does not - then just add a small amount of ascorbic - just a cup or so around the sides of the pool, and put the pool on circulate for a couple of hours. This should do it, you should not have to do a full treatment. The small amount of ascorbic should work without having to rebalance the whole pool again. It will take down the ph so just make sure it does not go under 7.0. When you get to this point it is just a matter of tweaking the water to get the right amount of sequestering agent to keep the stains away.:)

Will do mbar!!! Thank you so much! I've come a long way since I took that cover off - and I certainly couldn't have done it without the great people on Pool Forum. I've already learned so much (but what I don't know still could fill a warehouse, I'm sure!).

Quote:

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Originally Posted by mbar

I am not a chemist like chemgeek.

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Just for the record...I'm not a chemist either, don't have a PhD in chemistry, don't work in the industry, etc. I did major in physics & chemistry at Cal Berkeley (field major in physical sciences since they didn't allow a double major in those two due to too many overlapping courses, mostly in math). I rekindled my interest in chemistry when I got my pool 7 years ago and ran into problems when using Trichlor tab/pucks. Did some chemical research and found The PoolForum.

I totally agree with Marie that if the water is clear and there is no staining, then don't worry about the varying metal measurements -- at least one of them is wrong. The 5 ppm sounds suspiciously high, even if sequestered.

Richard

That's a lot of math, Chem Geek!

We do have staining - but we had a brown pool over the course of several days - on 2 separate occasions.

5 was the highest reading we'd gotten. Right after we filled and it turned brown, it was only a 3. It couldn't have gone up 1.5 times when significant amounts of new water hadn't been introduced. So, I agree with you CG - it is suspicious. Not to mention the fact that the boy who did the test looked all of 12.

I no longer have the desire to know what the iron level is. I think I was just caught up in it because we fought it for several weeks. Truth is - it's not interfering with anything right now, so who cares. If water turns, I'll filter it out again. Done. Moving on.

Thanks for putting up with my neuroses!

Sounds like you have a good handle on your pool at this point. Time to move on and just enjoy it now. Don't fret over every little speck or your pool will end up being all work and no play. Glad Pool Forum was able to help you. Now time for you to go have fun! Good luck.

Thanks Watermom.

The forum has been vital to our success. I'm sure I'll have other things crop up - but for now - we're almost there!

You may not be a chemist, but I would trust you in any chemistry questions that come along Chem Geek:D

Hey my picture turned up!

Marie,
What do you mean your picture turned up? If you are talking about your avatar, I've been seeing it for days.

This is the first time I saw it, but I tried to upload it a couple of days ago, and it says it failed:confused:

Weird! I have been able to see your avatar for days now! Wonder why you couldn't see it? :confused: