Alkalinity?

I know that lowering the alk is a slow process.

We uncovered the pool a little over a week ago 4/23. Was a little green so added bleach until I got a reading over 5 - that is the limit of the HTH drop kit I got at Walmart (can't wait for Ben's kit to come). I tested tonight and CL (it only tests TC) is still bright orange - off the chart.

I have a 14K gal AG pool and my numbers are:

TC = 5+
pH = 7.2
Alk = 190 (a purple color down from 240+ on the 23rd)
cal = 260
CYA = 40

I have added a bunch of dry acid and I still maintain a constant pH reading, but Alk is slowly going down. On the 26th, we added 7lb dry acid (dissolved in water), and again on the 27th. It has been raining the last few days, so I didn't get back out there to add more. We are aerating unconventionally, but it is working. We have a sump pump in the water with a hose attached to a spray nozzle and balanced on the edge spraying into the water like a fountain would.

Does this sound like we are headed down the right track? The alk test really changed color with fewer drops tonight, but is still very high. I will put another round of acid in tomorrow morning. It seems like I am really using a lot of acid. I haven't been able to find liquid muratic acid, or I would use it instead of the dry acid.

Any thoughts or advice?

Look for the liquid muriatic acid at a regular hardware store, usually near the paint. It's about $3-4/gallon around here.

I can't respond to your chemical questions, but look at the thread titled "lowering Alk -- fountain or ripple." http://www.poolforum.com/pf2/showthread.php?t=783

It has lots of similar info you are looking for. I'm in your same boat: high Alk, low Ph. I'm doing what you're doing and no one has said NO!!! STOP!!! So that's a good sign, I guess.

(I've added 2 gallons of acid to my 40,000 gal IG vinyl pool and I've lowered it from about 250 to 160-170 over the weekend. Ph is lower, but I'm aerating too, hoping to bring it back up. Have no idea how long that takes, tho...)

Jennie

Jennie and "Doc",

You each get a Gold Star!! :) IMHO, lowering alk thru aeration is a high level of understanding how your pool chemistry works. I cannot tell you how long it will take.....there's lots of variables perhaps most importantly how agressive you can get with aeration. HD/Lowe's has muriatic in the paint section.....pricey, tho.

Doc, you can dilute your pool test water by 1/2 with distilled. The Cl test will then double in value. (reading of 4 means you've got 8ppm) You could even dilute it by thirds and should be able to test reasonably well up to 15ppm. Ben's kit will remove any remaining unhappiness in your pool life!! :D :D

I'm pretty sure Ben has a sticky posted at the top of the "alkalinity" forum called "Step-by-step....." Check it out.

I did read the sticky on how to lower alkalinity and that is what I am following.

A quick question about the liquid muratic acid: Is there an equivalency between liquid muratic acid and the dry acid? In other words, how much muratic acid should I add at each time?

I think you'll find that it takes less muriatic acid than dry to get the job done, but there's not really an equivalency between the two....just add enough muriatic acid to get your pH down to the 7.0 - 7.2 range. mwsmith has a calculator at this link http://www.hal-pc.org/~mwsmith2/BleachCalc262.exe
that can help you figure out how much to add, based on your current pH.

Janet

I just don't get it.

How can I keep adding acid and still get no drop in pH or Alk? I put in the last 7 lbs of dry acid about 4 hours ago and there is no change in either reading. I did buy some muratic acid at Lowes this afternoon, so as soon as my husband gets home I will add some of it and let it work overnight.

I think I see what the problem is. I just noticed your chlorine levels are well above 5 ppm (bright orange on OTO test!) . If they are very much above about 10 then when you test pH the phenol red indicator is being converted to chlophenol red which is an indicator for a lower pH range! (some indicators are better than others...i.e. have a chlorine neutralizer built in, but this will only work to a point and some conversion of phenol red to chlorphenol red will still occur at high chlorine levels) It is entirely possible that your pH is below 6.0 now if your chlorine levels are very high! the color that chlorphenol red prduces at a pH of about 5.4 is similar to the one that phenol red produces at about 7.2! I suggest that you get your chlorine done at a pool store that uses an FAS-DPD titraton test (or buy such a kit yourself) and find out just how high your clorine level is. If it is above about 10 ppm then you should treat you pH readings as suspect until it drops down.

you will not see a deacrease in alkalinity until the pH starts to climb above about 7.4 so it might take airating for a while, given the low pH.

IMHO, I would not add any more acid right now until the CL levels drop to normal ranges.

First thing is to wait for the CL levels to drop below about 8 ppm and then test the pH. Once you know where it is then you will have a better idea what to do next!

Thanks for that explanation. I have Ben's kit ordered, so I hope it comes soon.

I am really surprised that my CL levels have stayed so high. I did wonder about the high CL bleacing the indicators. I will see if a local dealer does a titration test tomorrow.

On of the pH drop test kits I have has a chlorine neutralizer that should be added when the CL level is high.

Isn't one of the solutions in the Taylor2005 also a CL neutralizer? Maybe you just need to add more neutralizer before measuring pH.

Just to clarify:
Aerating does NOT lower alkalinity (TA). It raises pH without raising TA--and nothing else can do that.

When you lower pH, you drag TA down with it. If you raise pH with soda ash or borax TA will rise--more with ash than borax. So you aerate to raise pH.

So the process is a racheting process. Lower pH and drag TA down with it. Raise pH with aeration. Repeat until TA is where you want it.

Quote:

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Originally Posted by CarlD

Just to clarify:
Aerating does NOT lower alkalinity (TA). It raises pH without raising TA--and nothing else can do that.

When you lower pH, you drag TA down with it. If you raise pH with soda ash or borax TA will rise--more with ash than borax. So you aerate to raise pH.

So the process is a racheting process. Lower pH and drag TA down with it. Raise pH with aeration. Repeat until TA is where you want it.

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Actually, the TA (carbonate hardness, kH) is not lowered until the CO2 is forces out of the water by airation. (Lowering the pH simply shifts the ratio of carbonic acid/bicarbonate in the buffer to the carbonic acid side.) This forcing out of the CO2 by airation reduces the total amount of the carbonic acid/bicarbonate buffer system in the water. As the CO2 is forced out of the water by airation the shift is to more bicarbonate ion hence the rise in pH and the decrease in TA. The 'accepted way' (that does not work effeciently) of pouring a 'shot' of acid into the pool with no water movement to lower TA is supposed to work in the assumption that the local area of low pH created will cause the CO2 to 'gas off' in that area since it will create a high concentration of carbonic acid (CO2 dissloved in the water) in that area.

Quote:

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Originally Posted by mphare

On of the pH drop test kits I have has a chlorine neutralizer that should be added when the CL level is high.

Isn't one of the solutions in the Taylor2005 also a CL neutralizer? Maybe you just need to add more neutralizer before measuring pH.

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chlorine neutralizer (sodium thiosulfate) will work to a point but if too much it used it will also have an effect on the pH reading.

Quote:

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Originally Posted by waterbear

Actually, the TA (carbonate hardness, kH) is not lowered until the CO2 is forces out of the water by airation. (Lowering the pH simply shifts the ratio of carbonic acid/bicarbonate in the buffer to the carbonic acid side.) This forcing out of the CO2 by airation reduces the total amount of the carbonic acid/bicarbonate buffer system in the water. As the CO2 is forced out of the water by airation the shift is to more bicarbonate ion hence the rise in pH and the decrease in TA. The 'accepted way' (that does not work effeciently) of pouring a 'shot' of acid into the pool with no water movement to lower TA is supposed to work in the assumption that the local area of low pH created will cause the CO2 to 'gas off' in that area since it will create a high concentration of CO2 in that area.

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Evan,
While in terms of the actual chemistry, you are correct (as far as my limited knowledge goes), functionally (ie from the owner's point of view), the aeration simply raises the pH without raising the TA at the same time.

The underlying mechanism is as you describe--the effect is as I describe.

So the user's testing will show TA to fall when pH falls, then with aeration the pH rises but the TA does not. For the "How do I do it?" owner, this is sufficient. Usually, these are the folks who need help.

For the "How does it work?" types, your explanation is more precise.

BTW, the shot of acid method is not advocated here, either. It's good for ruining vinyl liners, though...:mad:

Carl, What you say is totally true. However, airation will have no appreciable effect unless the pH is brought low enough to cause the shift in ratio. I was only trying to clarify that. The 'shot of acid' method that just about everyone in the pool industy advocates will just lead to pH bouncing all over the place as you try to balance everything out. I wondered about it the first time I read it when I got my first hot tub and was learning how to care for it!:confused: It went against everything I had learned from my experience in keeping aquariums! When I first saw the PROPER way to do it on this forum I knew I found a home and advice I could trust!:)

Thanks for all the technical and not so technical advice. I didn't realize that the TA levels wouldn't drop until the pH started rising again. I am quite concerned about my pH levels now. I am afraid that they are too low. My biggest problem right now id that it is an 80 mile drive to Leslies. I will call the few local pool stores and what type of water testing they do, just to get back up testing. I know that my HTH kit is not the best, but so far it is the ONLY kit I have found locally. Home Depot doesn't have any pool stuff out yet and Lowes only has a 2 way kit and strips. Even the pool store that we got the pool from only sells strips.

If I have gotten my pH too low, should I just wait until the aeration slowly brings it up or should I add some borax to bring it up slightly (and the TA too)? How low is too low for pH?

IF your chlorine levels are very hight the only way to get an accurate pH reading is with a properly calibrated pH meter. Most pool stores do not use them, however. My opinion (and anyone please feel free to correct me if you think it is in error!) would be to:
1) let the chorine level drop to under 10 ppm (mix your sample of pool water with an equal amount of distilled water...a shot glass is a good measure) and then test it and multiply the reading by 2. This way you can test up to 10 ppm Cl instead of 5 ppm)
2) Then retest your pH and if it is extremely low add borax IN SMALL INCRIMENTS to bring it up to 6.8
3) Then follow the procedure in this thread exactly to lower the TA
http://www.poolforum.com/pf2/showthread.php?t=191

I noticed that you stated that the ALk was "190 (a purple color down from 240+ on the 23rd)" , Is the TA test in your kit a titration (where you add drops until the color changes) or is it comparing a reagent against a color chart, or maybe a test strip?(TA tests on pool strips are usually shades of green while TH ...Total Hardness... are blue to purple!) If it is not a titration test I would not mess with it at all until the water was tested with a titration test. This didn't register with me the first time I read it but as I reread through the post it set off a warning bell in my brain.

The TA is a titration test. 25ml of pool water, add 5 drops of the reagent and then count drops of the titration agent until it turns from green to red.

I haven't gone out to get any water yet today - my daughters have been high maintenance this morning. I will go buy some distilled water later.

I think I am concerned about the pH from the explanation earlier about the high CL level changes the pH reagent.

Evan and I are on the same page here.

The WalMart HTH 5-way kit is really very good, but with super-high chlorine levels you may have problems with pH.

I had forgotten to mention that pH must be at or below 7.2 for aeration to work.

I've been an advocate of the shot-glass method for years. You can even use 2 shots of distilled water to one of pool water to measure chlorine levels to 15ppm with the 5-way kit.

Unfortunately, if you don't have the chlorine neutralizer, it's tougher to get an accurate reading--unless you have the Taylor phenol red that has the neutralizer in it.

Made it out to the pool. I got the following readings:

TC = 5+ I don't have any distilled water yet
pH = 6.8 or below since that is the lowest reading on the chart
TA = 140 - was a solid red

You have two choices:
1) add Borax NOW to get your pH to 7.0, then aerate to raise pH.
2) start aerating now and that will raise pH. But you'll need a fountain to raise pH quickly.

I am torn on what to do.

I don't have a fountain, but I have the sup pump running with a sprayer head back toward the pool like a fountain. I also have the return pointed toward the surface bubbling the surface.

I don't want the pH to remain too low. I am going to test the water again this evening and decide then. I have some borax, so I might add a little.

Thanks again for all the help!!

test your tap water for chlorine. If it shows 0 ppm then you can use it instead of distilled water for the dilution. If it shows ANY chlorine at all you will need to get distilled water.

Your pump and fountain sound ideal for airating. It is a slow process so it takes some time.....

Stop adding any chlorine to the pool until the levels drop and then test the pH. You said your pH is now reading 6.8. That means that your Cl levels have dropped enought to not interfere with the pH test. If there was interference you would be seeing red to purple most likely. I would just let the Cl drop to about 3 ppm now since your CYA is at 40 ppm

You have been putting dry acid in which is milder than muriatic acid. It won't lower your pH as quickly or as much so I don't think there is any immediate danger. Someone with more experience with vinyl pools might know better.

Carl, Your take on this?

Go ahead and add some Borax and get that ph up to at least above 7.0.

I got the distilled water and used the shot glass method and Cl is 6. Not as high as I expected, but today was sunny and warm, plus the trees are dropping a ton of seeds in the pool. I haven't added any chlorine sine the first day.

I didn't add any borax tonight but will in the am, just to get it up to a measurable amount. I am thinking about 1/4 box at a time? Do I dissolve it first or just broadcast it?

I am excited that the Alk is down to 140. So once the pH comes back up I will repeat the process to get it down further. I am thing in the range of 80-100.

A quarter box at a time is fine - don't have to dissolve it or broadcast it. Just dump it in the skimmer while the pump is running, breaking up any clumps. Let the water circulate a few hours, retest and redose til you get to the desired level.

Hopefully this thread isn't too long, just wanted to update where I am.

Added approx 1/4 box borax and it didn't seem to make much difference. pH is still reading 6.8, alk is 140. Cl has dropped to 5. Because I was curious, I decided to check the pH of my well water (after 2 filters, a softener and a RO system) and the pH color was exactly the same as the pool. I thought that was interesting, but have no idea what to make of it.

Also, because I was curious, I used a leftover strip test. Those numbers were interesting: TC=1, FC=5, pH=6.8 and Alk=40 (not 140 as the drop test says). I just want to see how inaccurate they are I suppose.

I am going to the city tomorrow so I will take some water to have tested to see what they come up with. I did add another 1/4 box borax this evening.

When I agreed that 1/4 a box at a time was OK, I had missed how low your ph was. You need to get it up to at least 7.0 ASAP. Since it is still reading so low, add a half box of Borax at a time until it starts moving. Then, you may want to switch to 1/4 box at a time. Sorry I missed that. Aim for target of 7.4-7.6.

I thought according to the procedures for reducing alk that I want to keep my pH just above the lowest reading on my test kit and allow the aeration to bring up the pH without raising the alk at the same time??

6.8 is the lowest on the test kit I have and I am trying to bring it back up so that I know I am not below it. I thought I understood the procedure, but maybe I misunderstood.

Ok. I just reread through this thread. You are correct about allowing aeration to bring the ph without raising the alk at the same time. Your alk at 140 is fine. I wouldn't worry about lowering it. Go ahead and retest ph. If it is below 7.0, I'd bring it up with some more Borax as you have been doing. If it is at least 7.0, you can just continue aerating and it should come back up. If it does not, then you can add a little Borax.

Quote:

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Originally Posted by CarlD

I had forgotten to mention that pH must be at or below 7.2 for aeration to work.

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So, how do you raise Ph above 7.2 without raising alkalinity? I have been doing the same process as savdoc2. I am now down to Ph of 7.1 or 7.2 with alk at 110 (down from 300+ a week ago). My fill water has a Ph of 7.2 and I can't seem to get my water any higher than that with aeration. Then I saw your note (quoted above). Is that all the higher I can get it with aeration? Which would be good to know since my fountains have been running for a week and I'm sick to death of them.
thanks
jennie

You can just add a little Borax to the skimmer while the pump is running. It will raise ph without affecting alk. Just a little - ph at 7.4-7.6 is good.

Quote:

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Originally Posted by CarlD

Just to clarify:
If you raise pH with soda ash or borax TA will rise--more with ash than borax. So you aerate to raise pH.

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CarlD said that borax WILL raise TA. Is it just a little? I'm battling high alkalinity in my fill water all the time (300++) so I'm paranoid about adding anything that will increase TA once I get it into range. But PH of 7.2 seems a little low. But if aeration stops increasing Ph at 7.2, then I have to use something else, right?
Jennie

Borax will not raise your alk much at all. That is why it is much preferred over soda ash. If you want to try and continue aerating to see if the ph will come up on its own, that is fine. Then, if it doesn't, you can always add a little Borax. (And, actually having a ph of 7.2 doesn't hurt a thing. Just keep an eye on it that it doesn't drop too low.)

Jennie,
I guess I wasn't clear. Total Alkalinity is linked to pH and generally moves with it. If your pH goes down, T/A goes down. If your pH goes up, T/A goes up no matter HOW you raise it.

Except: Aerating when pH is 7.2 or lower is the only way we can "break" that link and get pH to up without T/A going up as well.

We can also raise T/A without raising pH (much)--by adding baking soda.

So using Borax to raise pH causes the normal linked rise in T/A.

But if you use Soda Ash it's like adding BOTH Borax AND Baking Soda and it causes T/A to rise a lot more than Borax.

Still, as WaterMom says, you can usually use Borax without worry. However, if you are still in the process of lowering T/A, and pH is 7.2 or lower, you can use aerating to raise pH as our normal procedure.

CAVEAT: If your pH is below 6.9 you'll want to raise ASAP with Borax, especially in a vinyl pool.

Thanks a ton you guys. I think I am really close. My Alk is 120. Ph 7.2. I think I need one more gallon of acid. The last one I added didn't seem to do much. I plan to bring alk down to 100 based on Ben's sticky (http://www.poolforum.com/pf2/showthread.php?t=191) and the fact that my fill water is HIGHLY alkaline.

So you are saying once I get Alk down, that it's ok to leave Ph at 7.2? I've aearated for two days straight with fountains at Alk 120 and ph at 7.2. I don't think Ph will rise anymore with just aeration. At least not with my fountain set-up. so I'll lower one more time, get Alk at 100, aerate to bring ph back to 7.2 and leave it alone.

Is there any compelling reason to bring my Ph up to 7.4-7.6 from 7.2? Honestly, it just never ever moves from 7.2 for long. so I'm not too worried about it being lower that 6.9 with my liner. In fact, even when adding a gallon of acid at a time it never went below 7.0. Maaaaybe it was 6.9 for a couple hours, but that was it.

Thanks again!
Jennie

Sometimes pools have a mind of their own of what ph levels they want to be. 7.2 will be fine.

I added a whole box of borax Wed & Thurs. Tonight the numbers look good:

TC = 3
pH = 7.2
Alk = 140
Temp = 58

So the alk is holding steady and pH is safe. Other than a lot of tree seeds in the pool it looks good. We'll clean the seeds up this weekend.

Should I try to get the alk down a little lower?
What is a good level to keep the Cl?

I see in your first post that you say your cya is 40. If that is still the case, a cl level between 3-6 is your target. Alk is fine at 140. Leave it alone. At this point, I think you're good to go. Time to enjoy your pool! Glad we could help.

Thank you so much for all your help. I learned a lot.

You are very welcome!