Ph Level Climbs Every Day

[waterbear]

Fiirst of all there is no way you can get a reading of 47 for this test. Using a view tube the accuracy is to 10 ppm! The scale on the tube is NOT linear so you can't assume that if it is slightly more than halfway it is a 7!. If it is closer to 50 than 40 call it 50 +/- 10 and be done with it! (that's how it's supposed to be done).

Second, you need to let the test develop for 3-5 minutes or it will read low. Also if your water temp is above 80 degrees some of the precipitate will dissolve and read low and if it is below 70 degrees it can take longer than 3-5 minutes for the test to complete. If you read it before that it will read low.

Since you are getting 50 ppm with only letting the test sit for 1 minute then I suspect that your CYA is higher than you are reporting.

CYA is CYA. If it's too expensive at Leslie's get it a Walmart or Ace Hardware!

[chem geek]

Also note that Cyanuric Acid (CYA) takes a very long time to dissolve so you may need to measure it up to a week later to know for sure how much you really have in your pool. Depending on where you added the CYA, in the skimmer for example, it might be mostly in the filter still dissolving.

[itabb]

Ok, I read it wrong. I keep forgetting that the higher the water is, the lower the number. The water line was actually just above the 40 mark. That makes is more like 37, but we can call it 40. I did not let it sit for 3-5 min. The water temperature was 82, I think.

So I need to do this test over again, clearly. 1 question: If I collect large sample of water, say a cup or so, and let it sit in the house to cool for about 2 hours to room temperature (78), then would the test still be accurate?

[waterbear]

Yes

[itabb]

FC 12

PH 7.2

TA 80

CA 375

CYA 50

Temp 85

Salt 3700

When I did the CYA test, I let the water cool in a bottle in the house for several hours. Also when I mixed the reagents, I let them sit for 5 minutes, with some shaking inbetween.

When I read it, the black dot was definately gone between 40 and 50. At 50, I could just barely make out the darkness of the black dot. A few more drops, and I wasn't sure if it was my imagination. A few more drops, and it was just white. So since it's greater than 40, lets say it's 50.

Notice I got my TA at a perfect 80!!! I'm pretty excited about that. When do you think I can start adding Borax. Borax will raise the PH, right?

[chem geek]

Borax will raise both your pH and your TA, though it won't raise your TA as much as pH Up (sodium carbonate) products. Adding 20 Mule Team Borax to raise your pH from 7.2 to 7.5 will cause the TA to go from 80 to 85. If you want to keep your TA level constant and only want to raise the pH, the way to do that is with aeration alone. You should get your pH up one way or the other since your water is on the corrosive side (with respect to plaster/gunite/grout) with a saturation index (my version, not Langelier's) of -0.5

[itabb]

I don't mind a TA of 85 for the benefit of having Borax in the pool. What quantity of Borax do you recommend based on 15000 gallons?

[waterbear]

Before you add the borax to 50 ppm (which is what I assume you want to do) first get rid of the chlrone demand problem you have been having and get your CYA into the proper range for your SWG (60-80 ppm). When you have that done then think about adding the borates to the water!

[itabb]

FC 6

CC 0

PH 7.6

Normally, when I burn off chlorine in the sun, PH drops. I did as Chem Geek suggested and airated all day. PH went up to 7.6 today and I burned off half the chlorine (12 to 6).

Should I just dump 4 lbs of conditioner (CYA) into the skimmer or should I do 2lbs, wait a week, measure, and add as needed?

[itabb]

As a follow up to my previous message, I entered the numbers into the spreadsheet. It seems to get a level of HOCI (as ppm CL2) above .050 with a CYA level of 80, I need over 10ppm of FC. Currently, with a CYA level of 50 and FC at 6, all the numbers are green. I'm not sure of my TDS right now. So I'm guessing based on 3700ppm of salt. Anyway, my concern is about keeping my FC at 10, which is not realistic. Should I be concerned? What should my FC be at with this information and with such a high CYA level?

            Initial    Goal    Difference
Measured pH        7.6    7.70    0.10
Total Alkalinity (ppm CaCO3)    80    80.0    0.0
Free Chlorine (ppm Cl2)    6.0    6.00    0.00
Cyanuric Acid (ppm CYA)    50    80.0    30.0
Calcium Hardness (ppm CaCO3)    375    375.0    0.0
Total Dissolved Solids (ppm)    4,000    4,000.0    0.0
Total Sulfate (ppm SO42-)    0    0.0    0.0
Total Borate (ppm Boron)    0.0    40.00    40.00
Total Ammonia (ppm Nitrogen)    0.0    0.00    40.00
U.S. Gallons        15,000    15,000    
Temperature (oF)        88    88    0
            
Total Chloride (ppm NaCl)    3840    3603.1    -236.5
Carbonate Alkalini (ppm CaCO3)    62.5    43.4    -19.1
Langelier Saturation Index (LSI)    0.04    -0.02    negative corrodes; positive scales
% HOCl (vs. Total Free Chlorine)    0.8%    0.5%    
OCl- (as ppm Cl2)        0.084    0.060    
HOCl (as ppm Cl2)        0.050    0.029    0.011 is approximately 650mV of ORP and is the minimum for sanitation; 0.1 total (0.05 HOCl?) kills most marine plankton (so possibly prevents most algae?)
Calcite Saturation Level (CSL)    0.75    0.67    CSL and CSI are more accurate than regular LSI
Calcite Saturation Index (CSI)    -0.12    -0.17    negative corrodes; positive scales

[chem geek]

Because the SWG super-chlorinates a portion of the water flowing through the cell and that this dosing is done frequently throughout the day, many SWG users are able to run with only 3 ppm FC at 70-80 ppm CYA with no problems so that is the usual minimum (the manufacturers say 1-3, but at 1-2 ppm quite a few users have had problems with algae). And yes, that is a disinfecting chlorine level of around 0.015 which is below the minimum of 0.03 and the normal target of 0.05 when manually dosing a pool with chlorine. A very small number of users found they needed to keep their chlorine level for their SWG at the minimum 0.03 disinfecting chlorine level which would be 6 ppm FC but that was mostly for keeping away mustard/yellow algae.

[EDIT]

My hunch, and this is just a hunch, is that having 3 ppm FC with 80 ppm CYA will work in an SWG pool if your periodically (weekly?) brush your pool surfaces to prevent any algae buildup in biofilms. Most green algae is free-floating so will eventually get zapped in the SWG, but if any get stuck on a wall or in a corner, then only the FC level in the main body of pool water will keep it from growing and 3 FC with 80 ppm CYA is below what normally is enough to prevent algae (but this depends on how "ideal" the algae growth conditions are which probably explains why a few pools still had a problem at this level).

[END-EDIT]

The spreadsheet color coding was for a nominal "target", not a minimum. It is "green" when at the target. It is "yellow" when below that target (I didn't have a separate color code for the "minimum" since Excel only lets you have 3 conditional colors). It is "red" when below the target but above the minimum possibly needed for disinfection (which is lower than that needed for algae prevention).

So while I would say that a non-SWG user would need to keep a minimum of 6 ppm FC so a typical "target" of 9 ppm FC (to allow for some drop), an SWG pool such as yours could get away with a lower FC level. You may find that it isn't as hard as you think to keep an FC level higher than 3 ppm anyway since the high CYA level seems to protect the chlorine from sunlight more. At any rate, I wouldn't go lower than 3 ppm FC, but with the SWG you could likely go lower than even the normal "minimum" of 6.

[EDIT]

There are other options that can help prevent algae and let you use a lower FC level and this includes using 50 ppm Borates in your pool. This has the additional advantage of acting as an additional pH buffer that is well suited to the rising pH that is typical in most SWG pools and seems to help with that problem (probably by killing algae so chlorine doesn't have to so you can lower your SWG output which lowers hydrogen gas bubble production which lowers aeration which lowers carbon dioxide outgassing which reduces the pH rise -- WHEW!). waterbear can tell you more about that as it has been very successful in his pool as well as others.

[END-EDIT]

Richard

[waterbear]

Slow down, take a breath and realize it's a pool, not rocket science. For your CYA at 80 ppm keep your FC between 3-5 ppm and see how it goes. If you start to get algae then bump it up a bit. You will soon find what works for your pool. Most of the SWG pools that I have seen do just fine in the 3-5 ppm FC range!

[itabb]

I just cannot justify pushing my CYA level up to 80. My chlorine has been very stable at 6ppm and my PH has been stable at 7.5. I run my pump for 6 hours a day, 4 during the day and 2 at night. I run an extra 3 hours on Sat and Sun. I run the SWG at only 15%. I keep the pool covered during the day when it is not in use, and maintain a water temperature around 90. I'm not trying to maintain a 6FC, that's just where it's been. If it dropped down to 4, I'd probably kick the aquarite up to 20%. We use the pool at least once a day, though usually in the evening. Just wanted to update you.

[itabb]

Little update. I pulled the Sta-Rite 3 filters today for cleaning, as I did 6 weeks ago. Rust colored water ran out of it as I cleaned it. I think I found all the metal in my pool. I am getting a few tiny isolated stains here and there around the pool. I count 6 so far. Tiny round rust circles. The iron must have come back out from the filter. Side 2 of the filters is soaking in cleaner right now.

I took a water sample to the pool store on Fri. No copper, no Iron. I think I'll toss in my mikes blue magic anyway. I suppose I should wait a day to put in the Borax? I expect FC to be around 8 when I get the pool started up again. Any issue with that level of FC and Mikes Blue or Borax?

[waterbear]

Little update. I pulled the Sta-Rite 3 filters today for cleaning, as I did 6 weeks ago. Rust colored water ran out of it as I cleaned it. I think I found all the metal in my pool. I am getting a few tiny isolated stains here and there around the pool. I count 6 so far. Tiny round rust circles. The iron must have come back out from the filter. Side 2 of the filters is soaking in cleaner right now.

I took a water sample to the pool store on Fri. No copper, no Iron. I think I'll toss in my mikes blue magic anyway. I suppose I should wait a day to put in the Borax? I expect FC to be around 8 when I get the pool started up again. Any issue with that level of FC and Mikes Blue or Borax?

Do you mean Jack's Magic Blue Stuff by any chance? Never heard of Mikes blue magic.

[itabb]

Yes. I went to the chemical bin and grabbed the bottle and was about to edit my post, but you caught me!!! I saw another post you have discussing the best chemical to be Jack's Magic pink stuff. How is Pink stuff different than Blue stuff, and should I be using Pink instead of blue to remove the iron I don't have which apparently stains my pool?

[waterbear]

Yes. I went to the chemical bin and grabbed the bottle and was about to edit my post, but you caught me!!! I saw another post you have discussing the best chemical to be Jack's Magic pink stuff. How is Pink stuff different than Blue stuff, and should I be using Pink instead of blue to remove the iron I don't have which apparently stains my pool?

Blue stuff will work fine if you have it. Pink stuff is general purpose. blue stuff has a higher chelation index for copper. Purple stuff is dedigned for salt water pools (I am guessing it helps sequester calcium more to help prevent salt cell scaling) All are pretty much interchanable, IMHO. I also like Proteam's Metal Magic. It's a bit less expensive and it works just as well.

[itabb]

Ok, next step . . . I added Borax today. BleachCalc.exe said add 245 oz borax. It wasn't nearly enough. I checked the PoolEquasions.xls and it says I need almost 600oz 20 mule team for 50ppm in a 15000 gal pool.

So with the Borax I added so far, my PH shot up so high that I needed 11 drops on acid demand to get to 7.6. That's somewhere around a gallon of Muratic acid. So I added most of a gallon. Not sure what the PH is yet, but it shouldn't be below 8 yet. With a FC of 12.5, I'm hoping the sun will lower it as it burns off chlorine. (yes, I got my titrates!!!). Borate test shows between 0 and 15.

So what should I do at this point, and what should I be watching for. I'd post the other tests, but I did not do them because the PH was so off.

I just noticed that the spreadsheet says I need 4.5 Gallons of Muratic Acid to raise to 50ppm of Borates!!! What an undertaking. How should I do this to minimize my use of acid?

[itabb]

Update to prior msg.

Pool guy says I should be using dry acid instead of muratic to control ph when adding borates. What do you think?

[chem geek]

For every pound of 20 Mule Team Borax added for borates, it takes 7.6 fluid ounces (about a cup) of Muriatic Acid (31.45% Hydrochloric Acid) to maintain the pH. It would take 10.3 ounces weight of Dry Acid (93.2% Sodium Bisulfate) to do the same thing. The latter adds sulfates to the water while the former does not and high sulfate levels may degrade plaster (the jury is still out on that one). Unless there's a reason the Pool Guy has that I don't know about, using Muriatic Acid is more pure as it does not add sulfates. It is a harsher acid in its applications as the fumes are nasty, but if you are careful then you should be fine. I usually just position myself upwind and hold my breath while opening and pouring.

BleachCalc is wrong about how much Borax it takes to raise the Borates level (this is a known problem and is due to an incorrect assumption of how borate levels are measured -- the "ppm" is for Boron, not for Boric Acid or tetraborate). For your 15,000 gallon pool, to raise the Borates from 0 to 50 ppm it would take 883 ounces or 55.2 pounds (11.7 boxes of 20 Mule Team Borax) plus 421 fluid ounces (52.6 cups or 3.3 gallons) of Muriatic Acid to maintain the pH.

[waterbear]

Update to prior msg.

Pool guy says I should be using dry acid instead of muratic to control ph when adding borates. What do you think?

According to Proteam you can use either muriatic acid or sodium bisulfate with Supreme, which is sodium tetraborate pentahydrate. Borax is sodium tetraborate decahydrate, only difference between the two is the first has 5 water molecules attached to it and the second has ten so on a weight for weight basis the pentahydrate form will raise the borate level faster. At work we ususally recommend muriatic acid when we sell a customer Supreme.

[itabb]

I did not realize how much Borax or Acid I would need. It's like $60 in acid and borax. Anyway, I got my pool up to 15ppm of Borates so far. I guess it is going to take a while. I noticed my eyes hurt now underwater where they did not before. However, the water does look "softer" and a little more crisp. However, I also detected some CCs.

FC 5.5

TC 6

PH 7.8

TA 90

Does the Borax hurt my eyes or is it the chloramines or the 7.8 PH?

Also, in that spreadsheet, how do I use "Combined Chlorine to Breakpoint"? I am trying to simulate what happened today. I know I currently have .5 CC, and I started the day with 12.5FC. I also know that the SWG will break down CCs in the cell, and that sunlight and the relatively high level of FC will also breakdown CCs. How do I account for all of that?

[chem geek]

The spreadsheet won't predict the amount of CCs. The purpose of the two sections under "CHLORINE USAGE" called "Creation of Combined Chlorine" and "Combined Chlorine to Breakpoint" which together are the same as "Net Chlorine to Breakpoint" are to see the effects on pH and TA when chlorine gets used up in these ways. This has nothing to do with borates.

So if you want to know what happens to pH and TA when you add chlorine to the pool, then you first set your "Free Chlorine" number under the "Goal" to be what you want compared to the "Initial" so that the "Difference" should show the incremental amount you want. Then in the blue section under "ADDED CHLORINE" you should see the amounts of different types of chlorine needed to achieve that FC level. Also, in the blue section under "CHLORINE USAGE" you will see a negative number of the FC level. Type in the amount of chlorine in the appropriate place (based on the type of chlorine you are adding) in the light-orange field ("Inputs" column) in the ADDED CHLORINE section. Then type in the FC difference as a positive number under the CHLORINE USAGE section. Normally, you just put this full amount under the "Net Chlorine to Breakpoint" section since that's what normally happens, but in your case you could put all but 0.5 ppm there and put the other 0.5 ppm under "Creation of Combined Chlorine". Then click on the "Calculate pH/TA" button and you will see the net effect on pH and TA which should show that in this case the addition and usage of a hypochlorite source of chlorine is not pH neutral and has the pH rise because the creation of combined chlorine increases pH instead of the normal decrease in pH from the more typical usage of chlorine to breakpoint.

Technically, what I described above is really two steps I did at the same time. First, one just adds chlorine as with ADDED CHLORINE amounts and then can click on "Calculate pH/TA" to see the effect on pH and TA. Then, you can copy the Goal values to the Initial values (especially for pH and TA and FC) and then set a new Goal value with a lower FC. You then enter that in the CHLORINE USAGE section appropriately (split among categories that you want) and then click on "Calculate pH/TA".

So I'm not sure what you are trying to figure out with the spreadsheet, but it won't tell you why your eyes are stinging or why you have combined chlorine. I'm pretty sure the stinging is from the CCs and not the Borates -- could also be the pH if that wasn't near 7.5.

[itabb]

What is the combined chlorine to breakpoint for? I guess what I was looking for was the effect on TA and PH when the .5 CCs were eliminated, which should happen pretty quickly in my case with the FC above 5. I'm trying to study this to determine if my PH will generally head downward as the SWG runs at 15% and holds at FC 6. I'm sure there will be some CCs, but they'll get destroyed in the SWG and somewhat in the general pool with the high FC.

The hypothesis I was testing on your spreadsheet is that if I operate my pool the way I have been, I will see a continual and very slow decline in PH operating the SWG at 15% and holding a FC of 6. This is what I see when I operate, so I wanted to see if held mathmatically.

What keyed me off was something you said earlier. The net PH change for generating 1ppm FC in the SWG is offset by the use of the 1FC for sanitation. Then I also read that breaking a CC has a very high PH change while creation of a CC has only a moderate PH change.

Incidentally, I know you knew this, but I have discovered for myself that the DPD is accurate only to 5ppm and that if you dilute to measure 5-10ppm FC, you will be off by 1-3ppm, increasing in inaccuracy as you go higher in PH. I suppose that is the bleaching effect. By 20ppm, it probably shows up as 12ppm. When my titrate test read 12.5ppm, my DPD read a bit lighter than 10ppm (guessing 8).

One other thing regarding the titrate test. It seems the power has an effect on the results. I did the test twice, to be sure I got it right. First test was 11.5, second was 12.5. The difference was that in the second test, I tapped the spoon against the side of the tube to be sure all of the dust popped off and into the sample. Can you recommend a best method for measuring out the powder? Also, I always use the 10ml because I figure that .5 increments is close enough to make good decisions. Do you agree or do you use the 25ml test for .2 accuracy?

[chem geek]

Oh, now I see what you are trying to do and yes, the "Combined Chlorine to Breakpoint" can tell you the pH effect for what happens when your 0.5 ppm goes away from superchlorination in the SWG or from sunlight. Just enter in 0.25 (I tell you why it's half below) in the light orange area and click on "Calculate pH/TA" to see the effect.

In a 10,000 gallon pool, adding 1 gallon of 6% bleach will raise the pH from 7.5 to 7.79 (and the FC would increase by 6.17). I calculated this by putting in 16 cups into the "Adding chlorine with NaOCl" light orange area. If two-thirds of this chlorine (i.e. 6.17 * 2/3 = 4.1148) were to combine with ammonia or organics, then the pH would further increase from 7.79 to 7.83. I calculated this by adding 4.1148 into the light orange field in the "Creation of Combined Chlorine" section. When such combined chlorine (CC) is broken down, it takes one chlorine for every two CC so half the amount of chlorine or 2.0574 ppm and this decreases the pH from 7.83 to 7.50 back to where we started (it's actually 7.501 so slightly more basic to the small amount of extra lye left in bleach to add stability). I could equivalently just put in 6.1722 in the light orange in the "Net Chlorine to Breakpoint" section to see the net result of these two steps. The reason for the two-thirds of total chlorine in the creation of CCs step is arbritrary since it's whatever amount of CCs you want to produce -- I used two-thirds since the breakdown of CCs needs half as much and I wanted the sum to be the initial total of 6.17. In your case, you would just use 0.5 ppm for the creation of combined chlorine and 0.25 ppm for Combined Chlorine to Breakpoint.

In your case for the breakpoint of 0.5 ppm CCs, you would enter in half that, or 0.25 ppm, into the light orange field in the "Combined Chlorine to Breakpoint" section. The reason for half is that it takes half the CC amount of additional chlorine to achieve breakpoint. The reason for the 10x rule for raising FC to "break" CC is based on ppm values of ammonia measured as ppm Nitrogen because it takes 3 chlorine molecules to fully oxidize 2 ammonia molecules so in a molar basis the ratio is really 1.5 to 1 but chlorine is measured in ppm relative to chlorine gas which is 70.906 g/mole while Nitrogen is 14.0067 g/mole and 1.5 * (70.906 / 14.0067) = 7.6 which is where the 10x comes from (the "optimal" ratio of chlorine to ammonia is around 8-10 to force the right reactions to occur). So you might ask the question, "so is the 10x rule when using CC measurements based on chlorine, not nitrogen, wrong?" and the answer is yes. If you are measuring CCs already, then it only takes half that amount of chlorine to fully oxidize (i.e. achieve breakpoint). I'm guessing that the 10x rule perpetuated because in the presence of CYA, the disinfecting chlorine level is so low that the breakpoint reaction would be too slow if you didn't increase the FC level by quite a bit. At 30 ppm CYA, the disinfecting chlorine level is about 1/30th what it would be without CYA (at a pH near 7.5) so using 10x the CC level would be more than 20 times what is needed so would bring reaction rates closer to what it would be if one used a 1.5x multiple without CYA. Sorry this stuff is so confusing. It took me a while to get this ppm, Nitrogen, Chlorine, etc. figured out.

Anyway, 0.25 ppm of chlorine to break 0.5 ppm CCs only lowers the pH from 7.5 to 7.47 so isn't even measurable. So I don't think you will see much of a pH effect from the breakpoint of your CCs. So if you are seeing a downward trend in pH, then it's probably from something else. If the overall FC was dropping, then that would be significant (say, from burning off from sunlight faster than your SWG replenishes it) but you said the FC was holding.

As for chlorine tests, dilution before using the DPD test shouldn't cause a problem. There shouldn't be any bleaching effect if you dilute the pool water (to below 5 ppm FC) before doing the test. You essentially produce lower FC water by dilution (assuming dilution is done with water that does not contain chlorine nor monochloramine -- i.e. NOT tap water, but filtered or distilled water). Nevertheless, the DPD test is a visual color test so isn't very accurate and when combined with the errors in dilution measurements, just gets worse. You're seeing a bigger effect than I'd expect, but the point is the same -- an OTO or DPD test is only good for a rough check of having chlorine, and is not accurate for knowing if you have enough if you are on the edge (if you are well over your target, then such tests should be fine).

As for the FAS-DPD powder, I found that there are variances in the test that are more a function of time than anything else. I've tried different powder amounts (1, 2 and 4 scoops) but through repeated measurements the only thing that was consistent was that the chlorine level would drop over time. I'm not sure whether this is from oxidizing contaminants in the vials (even though they were rinsed thoroughly) or from outgassing of chlorine or what, but it was definitely repeatable and this was from a single large sample jar (so avoids the variation from where I sampled in the pool). I think that the 0.5 ppm test is fine if you normally have high FC levels (probably because of high CYA levels and no SWG). I personally use the 0.2 ppm test because I usually keep my chlorine level near 3 ppm, but for regular measurements the 10 ml sample with 0.5 ppm accuracy is fine for people who manually dose chlorine. With your fine tuning your SWG which should get to a reasonable steady-state level of FC (unless your bather load varies or you have storms, etc.), you can use the 25 ml sample with 0.2 ppm accuracy, but it's really up to you.

Richard