Low PH level, how to measure, and iron staining situation

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copotay

copotay

0
Aug 7, 2011
146
Lafayette, La
Been trying to help my sister with her 16000 gallon fiberglass pool built in the 80s, she allowed it to get real bad full of leaves and basically a dark brown soup. So once I did the clean up, removing two years of leaves,with the water still dark brown I brought it to shock level for several days to kill anything that might have been living and growing in there. Once I got it pretty clear and allowed it to come down from shock, the pool developed brown stains all over making the pool water look greenish yellow even thought he water was clear. Figuring out it was iron staining with a vitamin C tablet, I followed the directions on the 2lb Leslies Stain Remover, bringing FC to 0 and PH to around 7.2 before applying.

One point of note is that when I tested the water for the first time for PH, after letting the FC go below 10, I got an extremely yellow reading, now I understand that this would be 7.0 or below, I believe below 7.0 cause it was so yellow. The TA was 30, so before I used the stain remover I had to add borax and some baking soda and was able to bring TA to around 150 and the PH to 7.2. This begs the question for future reference, how can I test lower than 7.0 ph with the phenol red so I can get an exact ph to plug into the caculator to add the proper amount of borax or baking soda? I have looked around the site and cant find the answer.

Well I added the Stain Remover, the entire 2lbs added a little bit more than it needed, and before my very eyes it started working on the stains, waiting 1 hour, then added Natural Chemistry Metal Free to as the sequestrant, (I now learned that is not a recommended one here). Waited 24 hours and backwashed. There are still some very light shades of staining left especially on the walls so I was wondering if another dose of the Stain Remover is needed now that its been 5 days and its still there, I have not added any bleach and have the FC still at 0. And I guess if I add another dose of stain remover, with it hopefully suspending the remaining iron deposit, I would have to follow up again with another dose of suquestrant. Looks like from what I have been reading you either have to replace the water or keeping adding suquestrant on a regular basis to keep the iron from redepositing on the surface since the sand filter will not remove it.

At first I could not figure out how the iron entered the water because we pull from the same city water supply and my pool never had stains and she has no heater or metal piping. My sister has a well pump with hard water, no softener, to water her flower beds and over the last two years she was running the sprinklers near the pool that eventually turned the concrete on one side of the pool yellowish brown. Seems the sprinklers were throwing hard well water into the pool too and it must have really built up then when I shocked the pool, which was never done before, it made the pool surface a very yellowish brown rustic color.

Any information greatly appreciated
 
It's not really practical to measure pH below 7 or so with pool test kits, so it's better to just add a little and measure. Even withing the range where the kit can measure, calculations of needed additions are still approximate because of other factors in the water and you should always add some and re-measure to make sure the result isn't excessive.

You will not get the iron out of the water without draining and refilling. Sequestrants are temporary and expensive.
 
You can not measure that low. Use 7 in PoolMath, add the borax, circulate for at least 30 minutes, test and adjust again if needed.

Why did you raise TA so high?
Does not sound liked you completed the SLAM process until passing the 3 criteria to stop.
 
tks for the nfo on the PH, I did not mean to get it that high, I plugged 40 in the caculator and 7.0 in ph using target of 100 and target of 7.2 for ph, I added what it told me to add, one box borax and 200 something ozs of baking soda.

So at this point I should SLAM it until the criteria is met and then let the FC fall to 0, then try the stain remover again?
 
The borax also raises the TA some so that is likely why you overshot. You should adjust the pH first, then recheck the TA before adjusting.

You want to ensure that there is nothing living in the pool before dealing with metal staining. Although if you are going to drain to get metal free water, that would be first I think.
 
Ok tks, I guess that might be the way to go, drain the pool since I probably will never get the iron out, just kinda worries me to take all the water out, heard horror stories of draining a fiberglass pool all the way out and the water table pops it out the ground. I dont think just slow water replacement, empty some out then replace, (two or three feet at a time), would work either, there would probably always be some residual iron in the pool since not all the water would be removed it would mix with the bad water.
 
Partial draining will remove the iron as well, just not all of it. If you did 25% drains you could reduce the iron for each drain to:
75%, then 56%, then 42%, then 32% .... so 4 25% drains would lower the metal by 2/3 assuming you have water for refill with no metal in it.
 
Tried draining half in two segments and refilling over three days with iron free city water, the same one that i use in my pool, it's no go, the minute I slowly raised the bleach by 1 ppm a day and I got to 3, it redeposited the stains just not as bad. Ph at 7.1 - 7.2 and has remained there along with FC holding. Guess my sis just gonna have to live with a greenish tint to her water with rust stains unless she wants to keep spending money on vitamin C and sequestrant
 
Thought I would just show some pics of how the iron returned to the walls and how a vitamin C tablet cleared some of it. I am going to crush some 3 dollar a bottle vitamins in a food processor as an experiment, should take about 3 bottles for the pool size. I know it will return without sequestrant but just to have fun.
You can also see in the background of the whole pool how the well water stained the concrete next to the pool from the sprinklers she had blowing about three years ago. Brought a sample to the pool store and they gave me a .35 ppm on the iron

photo.jpg



photo3.jpg
 

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Thought I would give an update on this pool. We have cleared it with another ascorbic acid treatment after doing about a 3/4 pool water replacement over several days. We cleaned sand filter over that period several times. Iron tested at two different pool stores with the water clear and blue. Let water circulate and filter for one week adding polyquat 60 and three pucks to keep the algae at bay. The pool stores, electronic testing and chemical testing, give me a 0 reading on iron, so thought I would give a try bumping up the chlorine yesterday to 1 since FC was at 0. PH 7.2. All test done with Fast DPD and Taylor test kit at home.

As of this morning FC is at .05 and the pool is a light shade of green. Well looks like there is still iron in it although the testing is showing 0. Thank God I did not shock it. I am at a lost, I know the next thing is to Ascorbic treat it again to clear and use sequestrant forever I guess. Goes to show you that even two separate stores show 0 Iron but its still there. The pool is very old fiberglass, with some pitting areas showing exposed fiberglass, wonder if the iron over the years has embedded into the exposed areas and will not come out until it contacts the chlorine and releases it but one would think that the testing should have revealed this once it would have been released into the water.

Forgot to add, very slight staining with the green tinted water this morning, I guess since my FC was so low, which does come off with a Vitamin C tab.
 
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I assume you mean the FC is 0.5ppm ... it does not measure down to 0.05 (you may have instructions with a typo).

You only need the Ascorbic to remove staining. If it is just the water, then you need to start using sequestrants. Oh, just saw the last note that there is some staining.

Metals are a real pain.
 
Natural Chemistry Metal Free is not one of the sequestrates we recommend. Sequestrants based on HEDP, phosphonic acid, or phosphonic acid derivatives are the most effective. ProTeam's Metal Magic and Jack's Magic The Pink Stuff (regular), The Blue Stuff (fresh plaster), and The Purple Stuff (salt) are some of the top sequestrants. You can also find many other brands with similar active ingredients, some of which are noticeably less expensive.
 
Tks Mike the stain comes off with the vitamin c tab and when we first tested we did have iron but according to the "pool store people" there may be such a minuscule amt that the test won't show but there still could be iron once u add bleach/chlorine. We put two puck floaters in 0 FC and after a couple of days the FC was still 0 pool was still clear but the vents on the floaters were stained brown where the chlorine melts out of. So we brought it up to FC 1 within 30 minutes the clear pool turned clear light emerald green. Loaded the sand filter with DE, pumped overnight. Next day backwashed once the sand filter was very restricted and cleaning the water real good. Brownish rust water came out and the pool water was clear and not green. I have done this twice so far and each time the water is less green upon adding the bleach. So it appears this may be helping to scrub the water. Time will tell. Btw also keeping polyquat 60 in it while at 0.

Jason, tks for the nfo just trying keep from going to the sequestrant yet to save money, but eventually may have too.

Here is a before and after, with the pool clear the FC is 0, the next picture is after going to an FC of 1 in 30 minutes. The last pic is a closeup of the floater and where the iron is reacting with the puck at the vents of the floater.

clearpic.jpg


green1.jpg


floater.jpg
 
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