Question: How do I bring down calcium hardness from CH 430?

Apr 28, 2008
19
#1
Hello folks,

I have just done my second complete test using the TF100 4/27 & 4/28/2008. Great kit though I would say a nice booklet one can read about the different issues each test addresses would be a nice addition to the kit. I bought the kit specifically for the calcium hardness issue I know I have. I have a 25,000 gal gunnite pool redone last year. I am running a Hayward D.E. 7220 and a Polaris eight hours a day. Had the sides pumiced with a scale removal chemical and then backwashed, added water and GLB Sequa Sol (54 oz first time around) to the pool and pH up to bring the pH up, shock to get the clorine up which were both down on a normal test kit the day before the TF 100 arrived. I then let the pool circulate for a day, the 26th. Here are the results of the tests, by date. Each test was taken at noon from the same place in the deep end of the pool and three hours after system started circulating and Polaris crawling around.

4/27 FC: 4.5 CC: 0 TC:4.5 pH: 7.3 T/A: 110 CH 430 CYA 70
4/28 Added water and about 20oz of GLB SequaSol Let pool circulate most of the day before I took test.
4/28 FC: 4 CC: 0 TC:4.0 pH: 7.3 T/A:110 CH 440. I did not take a CYA test this day.

If anyone can give their opinion about getting the calcium hardness down, a sequestering agent you might have experience with or something else you know will work. I'm in Thousand Oaks California so the heat is already 95+ and the sun is intense, so I know I'm going to be adding water almost every day for at least the next few months. Thanks to anyone who might be able to shed some light or offer suggestions.

Best,

Thomas
 

duraleigh

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#2
Hey, Thomas,

Point taken on the booklet. I am dedicated to keeping the cost as low as possible but that might be something to be addressed in the future.

What is the CH of your Fill Water? That's your best chance for success as CH is almost impossible to remove other than drain and refill.

If fill water is high in CH, then a partial drain and refill is of no useful purpose.

Now, CH of 430 is pretty high but not unmanageable. The key factor to living with it is careful managment of your pH and Alalinity. I won't get into the details because I'm not the best resource on the forum and it may be a moot point if your fill water is fairly low in CH.

Welcome to the forum :lol: :lol:
 

JasonLion

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#3
A sequestrant will help prevent high CH levels from causing scaling but it won't actually lower the CH level. Sequestrant binds to the calcium and keeps it from reacting as it otherwise would, but the calcium is still there.

The only practical way to lower the CH level is to replace water with new water that has a lower CH level than the pool has.
 
Apr 28, 2008
19
#4
Jason and Dave,

Thank you for your replies. The fill water is 90. I did the test twice. Both times it took nine drops to get it back to blue. So the water going in is 4.7 times less than the water in the pool @ 430. The pool is in ground, gunnite, one year old (sorry if I am repeating), clear water, getting slight brown stains here and there that started me on the sequestering journey. If my pool is 25,000-26,000 according to TF Pool calculator which seems perfectly in line with what I have calculated long hand, and if the calculator is telling me 43% refill for the CH and 40% refill for the CYA then I have a lot of changeover. Can I do this a bit at a time or do I take it down, below the tile, exposing the gunnite/plaster and then filling it back up or do I do it a bit at a time. I suspect the former but if there are a few ways, I would like to know them. Thank you both.

Best,


Thomas
 

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JasonLion

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#5
Why do you want to lower your CH levels? Eventually you are probably going to have to, but CH of 430 isn't all that bad. You just need to keep an eye on the PH (make sure it doesn't get too high) and perhaps lower the TA a little and you can continue for some time without lowering CH. CYA is also acceptable where it is. You don't have to hit every target number exactly.

You can replace water all at once or a little at a time. Doing it a little at a time takes a bit more total new water but works just fine.
 

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Apr 28, 2008
19
#6
Calcium

I had gone to the calculator on the site and understood the level of CH should be 260 not 430 and CYA should be 40, not 70 with each remedy being 40-43% changeover of water. The way I realized I had a calcium problem was in the scaling on brick and tile above the water line. That's really what is showing as a problem. No scale inside the pool that I can see when I brush it down, twice a week at least. So it started with my understanding I had to get it down to 260 to avoid the white scale on tile and brick. Am I wrong here? Thanks again.
 
G
#7
THIS is why I don't like the CSI (or LSI) and calculators that give you a saturation index!!!! It is a guide but it's NOT the predictor of scaling and no that much stock should be given to it, IMHO. The reason you have scaling is that you let your pH climb too high, period. pH is the MAIN factor to predict scaling. It takes very large changes in calcium hardness to make small changes in the scaling porperties of water but only small changes in pH!. You calcium is not that high and if you keep your pH in line then you won't have any problems. What form of chlorine are you using? If you are using an unstabilized chlorine then drop your TA to around 70 ppm and keep your pH below 7.8 at all times. If you are using a stabilized chlorine then your Ta is fine but the guidelines about the pH still apply. If you do this you should have no further scaling problems. If you have a SWG then it's slighly more complicated to maintain the pH but not that much more so, follow the guidelines for unstabilized chlorine.
As far as your CYA goes, if you are using stabilized chlorine STOP NOW and you can get by without having to drain, 70 ppm is managable. If you have a SWG then your CYA is perfect.

Calcium levels like you have are very common in new pools because of the curing of the plaster.
 

JasonLion

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#8
There are several different ways to adjust things to solve your problem and draining and replacing water is perhaps the most work/expensive of them. The numbers that show up in the goal column of The Pool Calculator are suggestions, not hard targets that you need to hit exactly. The most important thing when you CH is on the high side, as yours currently is, is to keep PH from going up too much, ie keep PH below 7.8 at all times and closer to 7.2 to 7.4 when possible. Hopefully, with a few adjustments of other numbers, we can eliminate that restriction.

Another thing to be aware of is that some accumulation of white residue above the water line is common and that tendency can never be completely eliminated. There will always be dissolved solids in the water and so water that splashes up and evaporates will leave some white stains. What we can do is make it more likely that water that splashes up and then drains down will wash off that residue, but that rarely eliminates it completely.

Evaporation leaves the calcium behind and refilling adds new calcium into the water. So over time your CH level will rise. Eventually you are going to need to replace water. To conserve water it is best to not do that too frequently. By lowering TA and keeping the PH under control you can postpone water replacement until the CH level is higher. How far you want to go with that depends on how much you want to conserve water. I would probably let CH get up to around 600 before replacing water, but you can do it sooner or later than that.

You can lower TA by adding acid to bring the PH down to between 7.0 and 7.2 and then letting natural aeration of the water raise the PH back up. The acid will also lower the PH, while the aeration will leave the TA alone, so over time the TA will come down. Depending on what you are using for chlorine, you can often lower TA down as far as 60, which will help with the white stains above the water line. The process I suggested will take a while but I don't see that there is any reason to hurry.

As Waterbear mentioned, your CYA level is acceptable but you don't want it going up any higher. Chlorine tablets contain CYA as do some of the granular chlorine products (those that contain dichlor). You should also avoid cal-hypo, typically sold as a powder, since that will increase your calcium levels. Bleach is a good choice, as is a SWG, since neither adds anything you need to avoid.
 
Apr 28, 2008
19
#9
calcium /calculator etc

Thank you both Jason Lion and Waterbear,

This site is a wealth of information and I appreciate your taking the time to share and advise. I feel a lot more confident now that I understand there is a range, not a hard hit that must be maintained - or you are off. First question I have is, what is SWG, Waterbear? Sorry, I am a novice but a quick study. I have chlorine discs that were bought by the pool guy who is long gone. I have also used shock. Is there any way I can determine if the cakes are stabilized or not? Or is it a matter of cakes = stabilized, shock granules = unstabilized? I'm assuming I'll understand what you mean about STOP NOW with stabilized chlorine once I understand what SWG is. About bringing the pH and TA down, I have pH Down - Sodium Bisulfate 93.2% and I have Muriatic Acid, 14.5%. Jason Lion seems to be suggesting Muriatic Acid, which I have no problem doing, I just want to understand the reason is because I want to effect both pH and TA? When you suggest bleach, are you suggesting a common house bleach to bring CYA down?

Thanks.

Thomas
 

duraleigh

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#10
SWG = salt water chlorine generator.

Cakes (most of us call them pucks) are stabilized. Granules can be either stabilized or not.

Thomas, review the sticky "ABC's of pool water". It'll give you the basics you need to go forward.
 

JasonLion

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#11
You should read some of the Stickies, see the link in my signature or the sub-heading of each page. They are full of good background information.

SWG - Salt water chlorine generator

Common household bleach, only use unscented or "original scent", is a great source of chlorine for the pool.

Almost all of the tablets are made of trichlor, which contains CYA, but there are exceptions. Powdered chlorine might be dichlor, which has CYA in it, or cal-hypo, which has calcium in it, or lithium-hypo, which is very expensive.

Sodium Bisulfate is often called dry acid and is an acceptable acid. Muriatic acid is usually cheaper and is just slightly better for pools.
 
G
#12
SWG is a salt water chlorine generator, usually called a salt water generator. It makes chlorine in your pool from salt added to the water by electrolysis.

Chlorine tablets are usually triclor, which is a stabilized chlorine but some are made from cal hypo, which is unstabilized. I am 99.9% sure that the kind you have are trichlor.
Granular shock is usually calcium hypochlorite, which is unstabizlied chlorine BUT dichlor, which is a stabilized granular chlorine, is also sold as shock.

Muriatic acid and sodium bisulfate will both lower ph and TA. Whenever you lower the pH you have also lowered the TA. The tricky part is bringing the pH up without making the TA rise but that is pretty easy to do by aerating the water. The reason we suggest muriatic acid instead of sodium bisulfate is because it is much more economical to use and does not add sulfates to your water.

Beach or other unstabilized chlorine sources won't bring your CYA down but WILL prevent it from rising any higher.

This sticky and this sticky might help explain some of the different pool chemicals if you take a few minutes to read them.
 
Apr 28, 2008
19
#13
Calcium Thank you

I'm on to the stickies. Thank you all for your help. I will keep the progress of this updated so others who might have the same problem can benefit.

Best,


Thomas
 
Apr 28, 2008
19
#14
UPDATE:

Okay, so I found out the pool is 18,000 gal and the spa 560 gal from literature the previous owner left here - he had the pool built. This meant the amt of DE I put in there the week before was way too much, so this is what I did. I did a good backwash and then added 60% of what the Hayward recommends. Let me explain. When I had the DE filters cleaned by hand, I didn't know if the two stages of manual cleaning - hose down and if that doesn't work, a barrel with TSP etc. a chemical wash to clean it all off. He didn't do that. He told me there was some stuff he couldn't get off and that was why it was at a base of 20psi when up and running - after he cleaned the filters. So, knowing I couldn't get it all out by backwashing, and he said some was in there already, and the guy at Leslie pool telling me 60-70% of what is called for on a full pull and hand clean.

I bled the top, added the DE added water, waited a few hours, tested, added chemicals and tested again today. Here is what I have:
FC: 3.5
CC 0
TC 3.5
pH 7.2
T/A 100
CH 350
CYA 40


According to the calculator, with a CYA of 40 my FC should be 4.6. Should I go for this or am I all right where I am. I understand that if the chlorine is too high it can add to the stain problem. No one uses this pool. So I am just balancing with out any activity at all. As always, thanks for your help.

Thomas
 

chem geek

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#15
Thomas,

The FC level that is about 11.5% of the CYA level, which is 4.6 for a CYA of 40, is a target level for manual dosing of pools and gives some leeway for fluctuation. The minimum FC level is around 7.5% of the CYA level which is 3.0 for a CYA of 40 (the Sticky here says 2.9, but that's close enough) and is a level that your pool should never drop below. So your 3.5 is OK if it truly stays that high all the time. If it fluctuates, then your safer targeting a higher level.

These guidelines are such that almost all pools will remain free from algae. They appear to work up to rather high phosphate levels of 3000-4000 ppm, but every pool is a little different and yours may get by with lower chlorine levels. However, following the guidelines gives a very high probability of preventing algae. In my own pool, I can tell the "critical" chlorine level where going below starts to get more rapid chlorine consumption and a dulling of the water while being above it has somewhat high chlorine consumption but the water remains clear. When I go further above that, the chlorine consumption levels out and the water remains clear -- this is when chlorine kills the algae faster than it is able to reproduce and faster than its introduction (from organic debris). For my pool, this critical value is in the neighborhood of 4% -- probably because the pool has a more normal level of nutrients including phosphates and nitrates and also because it is covered with an opaque cover much of the time.

Richard
 
Apr 28, 2008
19
#16
CYA Test making me crazy

Started today on a clorox ultra 6% regiment in place of the pucks. Went out this morning and at 9:30am here is what I got:

FC 1.5
CC 0
TC 1.5
pH 7.3
T/A 100
CH 340
CYA 60

added 1gal + of bleach.

AT 1:15 I tested again:

FC 5.0
CC 0
TC 5.0
pH 7.3
T/A 110
CH 320
CYA 100

This is the question: the CYA test. I can stand there and fixate on that black dot slowly adding a little at a time, waiting till the water clears and then looking hard to see it. Is this the way it is done? If not, and I just pour till the first time the dot seems to disappear, then I am above 100ppm. It seems the pH is holding strong but the T/A has gone up and the CH is going down which I am glad about. It is the CYA I'm concerned about and wonder if I'm doing this test correctly. Still getting slightly yellow/brown staining inside spa around one jet and near the drain. Also getting a similiar color stain to either side of the water fall that drops from the spa to the main pool. Just a slight two foot or even less drop from where it exits the spa and drains into the pool. Any advise, insights as always, appreciated. Will be monitoring it at the end of the day to see how much loss of Chlorine so I can start a regiment.

Best,

Thomas
 
Apr 28, 2008
19
#17
Thomas 4:35pm chemical read

I've just come in after testing again - third time today. It is now 4:30PM I tested this morning, mid day and now a half hour before the pump shuts down for an 8 hour day.

FC 6.5
CC 0
TC 6.5
pH 7.3
T/A 110
CH 340
CYA 100


CYA seems twice the highest recommended range of 30-50ppm T/A is a high also. . Need acid to bring pH down to 7.0 and then aerate as I've read on the site to get the pH back up? Or add some borax? Thanks.

Best,

Thomas
 
G
#18
Re: Thomas 4:35pm chemical read

tfnyla7713 said:
T/A is a high also. . Need acid to bring pH down to 7.0 and then aerate as I've read on the site to get the pH back up? Or add some borax? Thanks.

Best,

Thomas
You need to aerate. If you raise the pH chemically you will also cause the TA to rise again.
 

duraleigh

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#19
Re: Thomas 4:35pm chemical read

tf,

Your pH and Alk are absolutely fine.

Your biggest issue is the CYA. With a CYA of around 100ppm, your chlorine should stay up around 6-12ppm to ensure sanitation. That's a pretty high chlorine level and somewhat difficult to maintain.

For that and some other reasons, I would suggest you consider draining some of your pool to lower your CYA. A 50% drain and refill would get your CYA to down around 50ppm which is a very good number.

The rest of your test results require no adjustment at all.
 
Apr 28, 2008
19
#20
Refill water and aerate for pH

As always thanks for your responses. Question about aerating: Is the spa/pool boost setting on my Hayward valve a way to aerate? I also have the jets inside the spa. I will do a drain and fill first then see where everything is and go from there. - will report back next week.

Best,


Thomas