Endless Pool with High Alkalinity

Problems relating to pH and total alkalinity.
Increase ph, increase TA. Reduce pH, reduce TA.
pH chemistry advice and techniques for the pool.
Jeffm
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High Alkalinity

Postby Jeffm » Tue 09 Oct, 2007 16:36

Mr. C,

Thanks for your input, but I don't have the secondary pump. Didn't get the jacuzzi option.

If you're thinking of the power unit that generates the flow. Yes, that does really move the water, but the 6HP hydraulic pump in the basement makes a bit of noise (working on enclosure).

Really the best option is a little PVC pipe I've already drawn up, and just putting that on the return fitting. Less power consumption and alot quieter.

I do have a float....and had the tabs in there from time to time, but I think I'm switching to the bleach, and will just use the float when I'm going out of town etc..

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Jeffm
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High Alkalinity

Postby Jeffm » Thu 11 Oct, 2007 09:12

Well, I'm not done yet...but I must say that the rate at which pH increases with good aeration is impressive. I went from 7.2 to 7.8 in like 3 hours.

The downside is a very humid room...

Looking forward to putting more time into this tonight.
chem geek
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High Alkalinity

Postby chem geek » Thu 11 Oct, 2007 10:12

Too bad about the humidity. I didn't think about that since most pools are outdoors so the aeration doesn't have such side effects. The pH rise is fastest from the lowest pH -- so faster from 7.0 to 7.2 than from 7.6 to 7.8 -- so you can add acid whenever it goes up or just at regular intervals, whatever is convenient for you. The amount of acid it takes to lower the TA is independent of how frequently you add it or how far you let the pH go up between additions -- adding the acid before the pH goes up a lot just makes the process go faster but doesn't change the cumulative total amount of acid needed.

In 3000 gallons, every 100 ppm reduction in TA needs a cumulative total of 77 fluid ounces of Muriatic Acid (31.45% Hydrochloric acid) though you obviously don't add that all at once since you don't want the pH to go below 7.0. That should give you some idea of how you are doing and how much you'll need -- assuming the TA test was accurate.

To go from a pH of 7.5 to 7.0 at a TA of 400 requires 33 fluid ounces of acid and will lower the TA by 44; at a TA of 300 it requires 26 fluid ounces and will lower the TA by 33; at a TA of 200 it requires 18 fluid ounces and will lower the TA by 23; at a TA of 100 it requires 10 fluid ounces and will lower the TA by 13. That should give you a rough idea of what is required as your TA gets lower. I'm sure you'll get a feel for this as you proceed. You can see how it will take more frequent acid addition as you get to lower TA and you'll also find that the pH rises more slowly at lower TA (which is what you're really trying to get to). You could probably just get down to 80 and stop there and see how things go in terms of pH stability. I only mentioned 50 before thinking that your pool had a lot of aeration, but then realized you had high TA from the Soda Ash.

Richard
Jeffm
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High Alkalinity

Postby Jeffm » Fri 12 Oct, 2007 08:05

Well,l I was down to 250 ppm last night.

I modified my aerator pipe, so it fits underneath the cover. So, I can keep the humidity contained. The aeration and pH rise is much slower now. (I expected that) but wow...every surface of the inside of my sunroom has water on it from the previous night.

I also found another side effect of the aeration. Algae formation. Cl levels were about 3 ppm. I put in 1 cup of bleech for now, and guess I'll address the algae when I get done with the Alk.


Running the pump all day should get the pH way up again so I can put more acid in tonight when I get home.
chem geek
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High Alkalinity

Postby chem geek » Sat 13 Oct, 2007 21:25

The aeration probably outgassed the chlorine faster as well, so yes, the chlorine level needs to be kept up or else algae can form. Too bad you can't aerate the water and get the TA lower before it gets added to your pool.

I wouldn't wait to address the algae. I'd hit it with chlorine now or else it will just get worse.
Jeffm
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High Alkalinity

Postby Jeffm » Mon 15 Oct, 2007 09:44

Well right now I'm just trying to keep the chlorine levels high enough, it's coming out pretty fast. I think I put about half gallon of Chlorox in over the weekend, and I'm still under 5ppm


Alk was down to 160 yesterday, added another pint of Mur, will check when I get home today, but it's certainly working well. Shooting for about 80.
Will take a full reading of everything else once I get there.
chem geek
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High Alkalinity

Postby chem geek » Mon 15 Oct, 2007 13:19

I'm a bit concerned with all that water and chlorine coming out with the aeration in your indoor space. When this procedure is over with, you should be sure to wipe down all exposed surfaces that got wet. I'd hate for the water and chlorine to deteriorate your metal surfaces. Fortunately, the amount of chlorine is low, but what gets left over is chloride (salt) and that plus the water can continue to be corrosive just with the oxygen in the air. So wiping off the surfaces to get rid of not only the water but also the salt would be wise.

Richard
Jeffm
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High Alkalinity

Postby Jeffm » Tue 16 Oct, 2007 09:51

Actually after the first day, I modified my aeration pipe to run under the security cover. You hardly notice any difference now. It seals up the pool about 99%. So there is no condensation inside, and very little added moisture.

The aeration takes quite a bit longer now than it did the first day, but it's well worth the wait.
Jeffm
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High Alkalinity

Postby Jeffm » Wed 17 Oct, 2007 12:45

Took a water sample in, just to check my numbers:

Temp is usually 77F
pH 7.5
Alk 105
CaH 200 ( I thought it was higher)
Phos 500
TDS 1700
CyA 10 (I thought that was higher too)
DPDI 5

Index 0.5

So..I'll probably raise my pH just by using it. Anyway...Just about perfect. The TDS were a bit high he said...probably from all the jerking around I did trying to get the Alk down initially with acid and soda ash.
chem geek
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High Alkalinity and TDS

Postby chem geek » Wed 17 Oct, 2007 12:55

The TDS will be mostly salt -- sodium chloride. You've also got calcium and carbonate, but mostly it's just plain salt. So long as you use CYA in the pool, you should be fine. If you used chlorine without CYA, then you would be overdosing the pool with chlorine and that combined with the higher salt level can corrode stainless steel faster (chlorides inhibit the formation of the passivity layer that protects stainless steel from corrosion) and produces chlorine disinfection byproducts more quickly and oxidizes skin, hair and swimsuits faster. With your indoor pool, you don't need a lot of CYA, but should target an FC level of a minimum of 7.5% of the CYA level to prevent algae formation (though less likely in an indoor pool). If you use an algaecide, such as PolyQuat 60, then you can use a lower FC minimum target of 3% of the CYA level, but make sure the FC is high enough to not run out with usage. Right now, your 5 ppm FC with 10 ppm CYA is too high in chlorine. You can use Dichlor to easily add CYA to the pool since it dissolves readily and adds chlorine as well (i.e. you can use it as a chlorine source for a short time). You can also get pure CYA, but it takes a long time to dissolve, though can be done in a day or two if you hang it in a sock or panty hose over a return.

They reported a saturation index of 0.5, but it's really at -0.2 which is fine. I'm not sure how they are doing their calculation.

Anyway, congratulations on getting the TA lowered. You should find the pH to be more stable. Let us know how things work out.

Richard

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