Should I add Calcium?

[riverheightsnancy]

Numbers today:

FC 10
TC 10
CC 0
CYA 80
PH 7.2
TA 90
CH 180
Temp for water @ 66-68

Pool looked very clear. Cleaned and vaccumed it. Used the brush to move acorns and noticed a white chalky substance lifting when I brushed, primarily in the deep end. Pool has not been green. Chlorine has been holding between 8-10 for weeks. Do you think the chalky residue is calcium? Or old dead algae? I am confused about the saturation index and what to do next. Trying to keep PH on the lower end because I get continual staining due to hard water from my well. I plan on closing in about two weeks.

 

[JasonLion]

Yes you should add calcium. Your calcite saturation index is -0.68, which is into the "corrosion of plaster likely" range.

I'm not sure on the "white chalky substance", but with CSI that low it is very unlikely to be calcium (which would disolve).

 

[riverheightsnancy]

Any thoughts on why this might be happening? Always ran this pool in the 250 and slightly higher range for CH. I am wondering if this is too low for a concrete pool anyway. Had to add some fill water last week, which is high in Calcium and unfortunately, iron. You would think that this would help a little. About two weeks ago I dumped my last bottle of Jack's Magic pink stuff in, because my stains just keep coming back, do you think that might cause chalky sediment on the bottom?

The pool is still a little cloudy today, but I am pretty sure it is not algae.
Today's #s:

CL 10
FC 10
CC 0
PH 7.2
TA @ 85 (it was between 80 & 90)
CYA 90 (I know it is a little high-am using bleach and waiting for open next year to pump out water)
CH 210
Water Temp 68

One thing I did notice when I put the drops in for the CH test, the drops sit in the bottom and don't turn red at all until I swirl. When I add the next set of drops and after I swirl , they appear to float as tiny colored drops in the water. They change color eventually, but the color is not saturated through, it is like lots of small droplets of red color, that appear to the eye to change color. Does that make sense? In other words, during this test, the red and blue appears as tiny drops of color in the water solution. Is that common for this test?

Thanks for the help.

 

[JasonLion]

The CH test can do some strange things when there are metals in the water. I see spinning flecks that seem to glint in the light. As long as you can see the color change it is supposed to still work despite any drops/flecks/etc.

I would run with CH up around 400. That will be safer for your plaster given your other numbers.

There is sometimes some temporary cloudiness after adding either sequesterant or calcium.

Perhaps someone else has an idea about the chalky sediment. I would tend to assume it is just some blown in dust and not worry about it.

 

[mbar]

I have seen this chalky sediment a couple of times when a lot of sequestereing agent was added to get rid of stains. I think it does something to precipitate out calcium carbonate. Did the calcium go from 250 to 180? Did the alkalinity drop too? I was helping a friend this year get rid of stains, and she ended up getting a lot of sediment in her water - the water got very cloudy. Her calcium and alkalinity did drop, and that is what I figure happened. She put in a couple of different kinds of metal control products before doing the ascorbic acid treatment. It took a while to filter all of the substance out of the pool. If you just had some, I would think it was the Jack's Magic that just reacted and dropped some calcium carbonate out. I would just leave the calcium where it is for now and see if the chalky substance breaks down and filters out. You can take the calcium level back to 250, but when dealing with stains I would keep the calcium at the minimum levels for a concrete pool. I have found that higher calcium levels can add to staining. These are only based on my observations, so I don't have any concrete proof (no pun intended )

 

[riverheightsnancy]

Thank you mbar & JasonLion. I had a feeling that this might be the case. The calcium did drop, although I am not sure how rapidly, as I did not actually test for it at that time. However, about 7 weeks ago I was at 320, and now it is 210-180. Sometimes I have difficulty with knowing exactly when the color changes over due to the particles in the water. (previous post) The alkalinity dropped a bit too, from 110>85. PH has been pretty steady, but I also aerated the water a fews weeks ago to bring it up a tad.

One other question, I thought that perhaps this was the begining of another algae bloom, even though it was not green at all(my CYA is high-so the problem of maintaining FC is more work-I really want to drain 1/2 the pool next spring). I decided to bring the CL up to shock level to be safe. Will shocking affect anything if/when the CH is low? When I slowly added 2 jugs of bleach via the skimmer, you could see a white cloud sort of coming from the jet and slowly overtaking the whole pool. Would that be common in a situation where there is a CH issue, OR do I really have an algae issue? My pressure went up a bit, so I figure the filter is filtering out something anyway. I mean, if there is no algae or any other issue, should adding chlorine cause any type of visible reaction in the pool? My head says no, but I need confimation from the more experienced people on this site.

 

[JasonLion]

I haven't run into the process mbar describes, but I would imagine it must be similar to what happens with copper (calcium is technically a metal and has similar interactions in many cases). The solubility of copper goes down as the chlorine level goes up, which can cause the water to turn green or copper stains to appear. If something similar was happening with the calcium/sequesterant combination it would fit quite well with your description. The high chlorine level would spread from the return and cause a powder to fall out of solution. I am unclear on what the chemistry would have to be to cause that to happen, but the basic model fits your description perfectly.

 

[mbar]

Yes, this is very consistent with what I have seen this summer. It also happened to my water after doing the stain treatment and adding sequestering agent and clarifier. I thought the same as you, that I may have had som algae, but I am still not sure. I took my chlorine up to shock, and kept it there until the chlorine held - I am not sure, but I think the chlorine was getting used up breaking down the calcium carbonate. It did seem to break down the calcium carbonate faster and it filtered out. I too saw a cloud when I added bleach. However, my friend took her chlorine up to shock, and let it come back down to normal. It took longer for her water to clear. I am hoping to hear from more people - to see if this has happened to anyone else. I do know that once my water cleared, I had no other stains for the rest of the summer. So I don't know if was the Metal Magic that seems to work very similar to Jack's Magic, that caused the calcium carbonate to form, which may have combined with the metal and so it did filter it out. I have always heard that once metals were in the water, then the only way to stop the stains was to sequester them all the time. I am hoping that the Metal Magic has worked as it claims - which is to turn the metals to salts so that they can then be filtered out. I am still not convinced - but after having the cloudy water, and clearing it up, I haven't had to deal with any other stains this summer. Even when taking the chloirne up to shock levels, which I had to do a couple of times after storms, and heavy swim loads. Please keep me informed with your progress.

 

[riverheightsnancy]

Hi mbar, I have read many of your posts regarding the stain treatment and have followed it with fantasic results. I swear that my pool never looked better than when I dumped the ascorbic acid it. It didn't really cloud up, but the water was so sparkly! Anyway...I trust your opinion because I know the ascorbic acid treatment works, and you are in a similar area of the country so your conditions (i.e., weather) more closely mirror mine.

Anyway, here are the numbers today:
FC 25 (I shocked to be sure no algae)
TC 25
CC 0
PH 7.4
TA 100
CYA 90
CH 210

Pool remains a cloudy, but it is slowly clearing. Pressure on the pump is maintaining a steady 12-13 PP, I don't think it is filtering anything, nothing major or quickly that is. I can still brush seidment off of the bottom, which then reclouds the water. The sediment is not easily picked up by the vacuum. Which I don't really understand. It will kick up when brushed, but when I use the special roller vac head for concrete pools,. it does not pick this stuff up. Was wondering if I could use a vac head with a brush? (any thoughts-I was under the impression that those were for vinyl only)

The other thing I do not understand is the slight drift of the PH & TA. I have added only (and I really mean it) clorox bleach 3 x 1.5 gallons. I am not aerating the water, you do see rippling, but it is not bubbly at all. We have had some evaporation of the water, and here is the question: will that affect the chemical balances? For example, I know splash out will help the CYA go down, but does evaporation? When pool water evaporates, does it take the suspended chemicals with it? I was just curious about that in trying to figure out the PH / TA increase.

Not sure what to do at this point. I have a bottle of floc, thought that I would try that. Pool has a very light stain all around (as usual). Still not sure if I should add calcium, am really on the fence about that. Will probably have to add fill water due to no rain and evaporation. The fill water is very hard and contains calcium. I am assuming that cement pools should not brush up dusty clouds as a byproduct of having a cement pool. Seems commonsensical.

My pool seems to get constant recurrent stains. However, even though I was maintenace dosing, maybe it wasn't enough? My pool was SOOOO heavily stained I used 12 pounds of vitamin C when I did the treatment. I tell ya it looked so nice after the treatment. I am thinking that maybe I need a complete water refill next year? Start over and fresh. We have been toying with the idea of a resurface due to the fact that the surface paint of the pool is coming off and the texture is rough and inconsistant on the feet. I don't mind, it makes it not slippery. My pool is very old, but well built. I would like to get through one more year before an overhaul. I am wondering about the metal magic product. I have only used the Pink Stuff.

Thanks for your thoughts.

 

[mbar]

First thank you for the kind words. This is what I would do.:

I would not add any flock. My friend did when she had the chalky substance, and it didn't help much. If yoiu have a skimmer sock, or an old pair of tights (you can cut the foot off and use it instead of a skimmer sock), us this to help catch some of the chalky stuff - you can even put a coffee filter in the basket to help filter out such tiny particles. Keep the filter running 24/7, and have patience - it will clear up. You can use a vacuum with brushes, but it will only push the stuff up again anyway. You can try holding the vacuum off the floor about 1/8th of an inch and see if that works, but I think it will just take time.

Something is reacting to make the calcium carbonate fall out of the water - I would think it was the Jack's magic along with the ascorbic acid treatment, it is just strange as to why it took 2 weeks to react :? And why it would too :? Anyway to answer your questions, the only reason cya goes down with splash out is because you add more water to bring the pool level back up. The chemicals do not evaporate with the water, they stay in - that's why the only way to get calcium and cya down is to dilute the water by draining some out and putting new water in. My ph tends to go up when I am just using bleach, so sometimes I use acid to get it down, and sometimes I use a trichlor puck (make sure there is no copper added to pucks!). The balance could be messed up for a variety of ways - especially with a sequestering agent in the water. The sequestering agent is acidic, so when it is gone, the ph will slowly rise, kind of like if you stop using pucks. The sequestering agent gets used up with the chlorine. I does break it down. It is very confusing, because everyhing that goes into the water effects it in some way - which can mess up the chemistry. It is really hard to figure out, because sometimes I think the water has a mind of it's own and just doesn't react the way you were expecting

I think you probably didn't use enough sequestering agent when you did the treatment. I always keep a close watch on the pool right after the treatment and add more sequestering agent as soon as I see stain starting to rear it's ugly head . Most often if you take the ph down to 7 and add sequestering agent the stain will lift back off. I would hold off on adding any calcium, Especially untill the water has stopped precipitating. All of your numbers look fine, and I would only worry about the cya for now - 90 is pretty high, you need a minimum of about 7 chlorine at all times. It may be worthwhile for you to do some water replacement now - it will help to clear the water while getting the cya down. Then if your calcium is low, add a little with your fill water. A level of 250 would be fine. If you are going to close for the winter, then I wouldn't do anything at all. Stains tend to disappear over the winter. Hope this helps, ask any questions you may have

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