insanely low pH and alkalinity -- chemicals didn't help

[CrazyMan]

After getting a ton of algae all at once I had my 30' round pool water examined. Turns out pH was < 6 and the alkalinity was just above 0. So I bought some supplies (25 lbs of alkalinity increaser and 5 lbs of pH increaser), did the alkalinity increaser yesterday -- all of it in increments --, and half of the pH increaser today.

I let it all settle and guess what? NOTHING CHANGED. The pH is still 6 or below, and the alkalinity is still 0. The guy at the pool place was shocked and said maybe the pH was initially too low. Anyone know what gives?

Oh, and next time, I'm not buying the supplies from the pool store if I can just buy them from Aldis. Spent enough already.

[chem geek]

He is right, your pH is probably very low. If the Total Alkalinity (TA) test turns red initially (instead of starting out green and then turning red) which I believe is the case in your situation since TA was measured as 0, then this means your pH was below 4.5 which is very low. If you have a vinyl pool, then it could be ruined and your pumps, heater, and filter could also be damaged.

And yes, you need to add more pH Up (sodium carbonate -- if you find Arm & Hammer Super Washing Soda, not the laundry detergent, to be cheaper than pH Up, then buy it since it's identical). And Alkalinity Up is identical to Arm & Hammer Baking Soda.

Richard

[Guest]

The TA test doesn't turn red, it starts at yellow dry and turns greener with more TA. It just became very slightly green.

[chem geek]

At high chlorine levels, the TA test goes from blue to yellow instead of from green to red, so if it started out yellow then that's the same as starting out red (at lower chlorine levels) and that means your pH is below 4.5 which is very low. Add Arm & Hammer Baking Soda and Arm & Hammer Super Washing Soda (not the laundry detergent) right away.

If your 30' (diameter) round pool is 48" (4') deep, then it has 3.14*(30/2)^2 * 4 = 2827 cubic feet which is 21,150 gallons. If I start out with "normal" pool water chemistry parameters and then add 30 3" Trichlor pucks to your pool, which would add about 165 ppm Free Chlorine (FC) over time, it would also add about 100 ppm Cyanuric Acid (CYA) and would result in a pH of 3.53 with a TA of -14.6 which would measure as 0.

If I then add 25 pounds of Alkalinity Up and 2.5 pounds of pH Up then I get a pH of 6.4 and a TA of 219. Since you are still measuring a pH of below 6.0 it means that your water probably had an even lower pH than I assumed. Also, with the pool store having you add so much Alkalinity Up, your pool has too high a TA. However, you really need to test the Cyanuric Acid (CYA) level since I suspect it is well over 100 and the only solution for that, I'm afraid, is dilution which means a partial drain/refill of the pool water. You won't be able to easily get rid of the algae nor maintain the pool with the high CYA level.

Though you could add more of the pH Up, it won't make the pH budge very much because the TA is now so high. Go ahead and add the rest since you already bought it but I suspect the pH will still be low. The easiest way to get the pH up higher at this point without adding to the TA will be to simply aerate the water -- turn the jets up, run any waterfalls, fountains, spillovers, hook up a shower using a return or a small submersible pump (such as a pool cover pump), or use an air compressor or pump to blow tiny air bubbles through a nozzle or pipe with small holes and put the end into the deep end (or bottom) of the pool. Just aerate any way you can -- you've got too much alkalinity in the water now so forcing out the carbon dioxide will cause the pH to rise.

Of course, since you're going to likely have to do a partial drain/refill anyway, you can start on that whenever you can. And please get yourself a good test kit, either the Taylor K-2006 from Taylor here or from Leslie's here or the even better TF-100 kit from tftestkits here. These kits contain the highly accurate FAS-DPD chlorine test which can measure up to 50 ppm FC and does so by counting drops (rather than comparing intensity of colors) and measure both Free Chlorine and Combined Chlorine with an accuracy of 0.2 ppm or 0.5 ppm depending on sample size. The kits also measure pH, Total Alkalinity, Cyanuric Acid (CYA) and Calcium Hardness (CH). Take charge of your pool.

I strongly suspect you got into this problem because you used Trichlor tabs/pucks as your source of chlorine and you didn't add any pH Up to compensate for the pH since Trichlor is very acidic.

Richard

[CrazyMan]

Thanks for the detailed response Richard. I sure haven't used 30 of those tabs this year -- maybe 12 to 15. At first I thought, oh crap, my pool is probably in deep trouble, but it's looking more promising (I think) after this last test I did (put in 7 lbs baking soda and 5 lbs alk+ stuff). Here's the numbers measured by my "AquaCheck" test strip:

pH - 5.5 to 6 (low)
TA - 100 (good)
free chlorine - 2 (good)
CYA - 20-30 (little low, pH might be messing up the test though)

So it's better than before. Maybe I can just try some standalone pH increaser over time and see if it will raise the pH, and check the CYA level once/if pH gets high enough. Does this sound like it has a decent chance of success?

Thanks

[chem geek]

Test strips are notoriously inaccurate with a few exceptions (for Borates and salt), but the thing to do would be to aerate the water since that should raise the pH with no change in TA. That is if we believe those test numbers.

If your [EDIT] CYA [END-EDIT] is really 20-30, then you only need around 3 ppm FC or so as your target to keep away algae, but it's OK to have it a little higher while you are making adjustments. Just make sure the chlorine level doesn't drop quickly. If it doesn't stay constant overnight, then there's still something consuming chlorine, possibly algae still trying to grow -- if that's the case, you should raise the chlorine level higher; if not, then keep the FC as is.

So, aerate away and you should be OK. But please get yourself a better test kit. It will be worth it and it lasts around 2 years.

Richard

[CrazyMan]

Ever since I saw something about aerating 6 or 7 hours ago I have had the blower blowing up as much as possible. I'll keep it like that all night and test in the morning. Might get one of those test kits too and actually check more than once a year, it will definitely help me avoid this hassle, LOL.

[CrazyMan]

Also... I've seen that I need to add Sodium Carbonate to get the pH up without affecting other levels. Is there a common product I can buy that isn't a crazy pool store price?

[chem geek]

No, no, no. pH Up doesn't just raise pH -- it also increases Total Alkalinity (TA) -- of course, the pool store's don't usually tell you that. Technically it is identical to adding lye plus Alkalinity Up. pH Up is just sodium carbonate and is identical to Arm & Hammer Super Washing Soda (careful: not the laundry detergent) and is also sometimes called Soda Ash.

Alkalinity Up is sodium bicarbonate and is identical to Arm & Hammer Baking Soda. It raises the Total Alkalinity (TA) and also increases pH a little bit.

To raise the pH while not adding to carbonates and not raising the TA as much, you can use 20 Mule Team Borax. You add twice as much by weight as you would pH Up to get the same rise in pH. Another alternative is to use lye / caustic soda / sodium hydroxide but that's harder to find (though it's used in making soap). You use about 40% as much lye by weight as you would pH Up to get the same rise in pH.

To raise the pH with no change in TA, you aerate the water (as you are now doing).

For acid, you usually use Muriatic Acid (31.45% Hydrochloric Acid) though that's nasty stuff that fumes. You can sometimes get some that doesn't fume as much or get a weaker concentration (often at the same price! as if they're fooling anyone!). You can also get Dry Acid (sodium bisulfate), but that adds to sulfates so I try and avoid that -- it's not terrible unless you use it all the time.

And you already knew about how bleach is the same as chlorinating liquid except not as strong. You need to use unscented bleach and some off-brands are very weak -- off-brand Regular may only be 3% or less. Clorox Regular is 6% while most off-brand Ultra bleach is also 6%.

Richard

[CrazyMan]

Ah yes I see that now. Your spreadsheet is very helpful. I ended up sticking a sump pump with its input about 4 inches below the surface and the output right above, and it's now blowing out and up like crazy. The pH has come up a little since last night but is still low 6's, and the free chlorine did drop. I'll probably add some sodium dichlor (maybe a half a pound) to bring the free chlorine back up while continuing the sump pump.

[chem geek]

Dichlor adds to CYA so unless your CYA is low, do not use it. For every 1 ppm FC added by Dichlor, you also increase CYA by 0.9 ppm. Use unscented bleach or chlorinating liquid instead to raise FC without raising CYA (or CH -- Cal-Hypo raises CH -- for every 1 ppm FC raised by Cal-Hypo you also raise CH by 0.7 ppm).

Richard

[CrazyMan]

Refill is done and things are looking much better.

pH = 7.0 to 7.2
FC = 0
ALK = 100 to 120
CYA = 0 to 10

I'm guessing the best thing to do would be to raise the CYA a little (maybe to 25 or 30), then add some sodium hypochlorite to up the FC to around 5 (and pH a little), then finally adjust the pH to 7.5.

Then wait for the FC to come down and the temperature to go up, clean the pool, and actually go swimming!

Oh, and I think I'll use liquid chlorine instead of the tablets from now on and test the water a little more than once every 2 years...

[chem geek]

I calculate that for your 21,150 gallon pool (assuming that's right -- you can see my calculations for that in an earlier post above) 10 pounds of Dichlor (dihydrate) would add 31 ppm FC and 29 ppm CYA to your pool so you could use that, not all at once, to add both chlorine and CYA at the same time since Dichlor quickly dissolves. This is much more convenient than separate CYA since that takes a very long time to dissolve (it's less expensive, but with the Dichlor you also get chlorine so the net price isn't that much more). I suggest testing the CYA level after you've added half to two-thirds of the 10 pounds, just to see where things stand.

The Dichlor will be acidic when the chlorine gets used (the initial addition is only slightly acidic, but chlorine usage is much more acidic -- that's why bleach or chlorinating liquid are really pH neutral when chlorine usage is taken into account). The Dichlor and chlorine usage would have the pH drop from around 7.1 to 6.74 so to get the pH up to 7.5 you can add 21.3 pounds (4-1/2 boxes since each is 76 ounces weight) of 20 Mule Team Borax. This will raise the pH without raising the TA too much. Another option, since your TA is already high enough, is to just aerate the water. Even turning up the eyeballs on the returns helps if it breaks the water surface, but using a waterfall, shower, spillover or especially an air compressor/pump with a nozzle or hose with tiny openings to produce tiny bubbles in the deep end works really well. Aeration will cause the pH to rise with no change in TA.

After you've reached your CYA target, then switch to using unscented bleach or chlorinating liquid. You may need to add this every day if your pool is not covered and is exposed to sunlight. If you want to automate the addition of bleach or chlorinating liquid, you can look at getting ezpool dotcomThe Liquidator.

Richard

[CrazyMan]

I have bags of Sodium Dichloro-S-Triazinitrone labelled "Quick Dissolving Shock". Is this the Dichlor to which you are referring?

[chem geek]

Yup. That's Dichlor.