Minimun Phosphate Levels ??

Algae problems in swimming pool water.
Green (cloudy) water or slimy pool walls.
Black algae. Mustard algae. Pink or white pool mold.
chem geek
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Phosphates in pool water

Postby chem geek » Sat 08 Dec, 2007 14:14

hoodfigga wrote:Just when I thought I had it all figured out they test my water and give my a Alkalinity result with correction. Here we go again I said to myself. Corrected Alkalinity what the heck. Turns out after some research you should correct your total alkalinity numbers by a percentage of your cya reading to get a true alkalinity number. Am I right. I hope so because I thought my alkalinity was 100 but they corrected it to a much lower number.
So now I need bicarbonate right.

I do have one question about the pool acid they sell. They use sulfuric acid. The container claims it has low odor and fumes, and it does. That muriatic acid got me few times real good right in the lungs. I tried to do some research but I really could not find a reason for using sulfuric acid vs Muriatic acid. Any thoughts??

Lastly I started using a pool blanket in the winter months trying to collect heat and save some penny's on the heat pump bill. What can I expect as far as chemical water changes. More chlorine , less chlorine, acid, alk, what effect does covering the water have on the pool chemistry. If you have any links please provide them.

The adjustment for Total Alkalinity ONLY applies to the calculation for the saturation index, not as an isolated number by itself (as far as "ideal ranges" is concerned -- such ranges having already taken into account the CYA normal range). You can always have a higher Calcium Hardness and/or pH to compensate for a lower TA. An absolute number, even adjusted, is not that useful. I doubt very much that you needed to increase your TA. A higher TA will often lead to a tendency for the pool to rise in pH over time due to the increased outgassing of carbon dioxide (TA is mostly carbonates making a pool essentially over-carbonated, like a lovely tasty beverage!). If you post a full set of numbers (FC, CC, pH, TA, CH, CYA, Temp), then I can give you more info.

I would use Muriatic Acid instead of Sulfuric Acid. Sulfuric Acid results in an increase in sulfates whereas Muriatic Acid results in an increase in chloride (salt). The sulfates aren't bad, but in higher concentrations may cause some problems though this is not definitive, but I'd rather just avoid that issue entirely. As for the fuming of Muriatic Acid, you can either just use it making sure you are upwind from it or hold your breath (or breath turned away) or use a lower fuming Muriatic Acid -- you can get half-strength that doesn't fume as much, but you need to use more and it costs almost the same. You won't be adding acid that often (or shouldn't be) so if you want to use the Sulfuric Acid you've already bought, that's fine.

It sounds like you've hit upon a reasonable method for cleaning your filter.

The main change with a pool blanket is less evaporation of the water and protection of the chlorine from breakdown from sunlight. So fill water amounts should drop and chlorine usage should drop, though in the winter it drops anyway due to lower temperatures. One thing you might notice is that the pH rises as the water temperature lowers ( from around 7.5 to 7.8 ) and that is normal even if the pool is covered.

Richard


hoodfigga
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Phosphates in pool water

Postby hoodfigga » Mon 10 Dec, 2007 06:25

Ok here are my numbers. Its a little late on the bicarbonate. I already added it to the pool.

FC 4
CC 0.5
pH 7.6
TA 120
CH 320
CYA 80
Temp 78

When I did my CYA test using the taylor 2006 it seems that the disappearing black dot is very subjective. The pool store tested my cya at 80 and I would say the dot disappeared at that point. If I had not had a predetermined number in my head, I wonder what I would have chosen as my cya reading. If you have any tips on reading the black dot please share them with me.

Thank you
15000GAL / Diamond Brite Classic / Aquarite SWG / 1.5hp Strarite / Hayward C17502 Cartridge Filter / AquaCal 155A Heat Pump /Sunny South Florida
chem geek
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Phosphates in pool water

Postby chem geek » Mon 10 Dec, 2007 13:58

Well, when you run your SWG, you will probably find a rather strong tendency for the pH to rise because the TA is at 120 ppm. That's too bad they had you raise it so high. It only makes sense to have a high TA when using an acidic source of chlorine such as Trichlor. The SWG produces hydrogen gas bubbles at one of its plates (it produces chlorine gas at the other plate and that dissolves in water) and these hydrogen gas bubbles strongly aerate the water pulling the carbon dioxide out of the water and into the air. That causes the pH to rise.

So a lower TA level helps reduce the problem since TA is a measure (at least partly) of the amount of carbonates in the water. A pool is over-carbonated like a beverage (though not as much, obviously) and just like stirring up a beverage or blowing bubbles in it through a straw makes it go flat, an SWG also makes it "go flat" and the pH rises as a result.

There is a LOT that pool stores do not know. The fact that a higher TA leads to a faster rise in pH is one of them. The fact that a high CYA level leads to algae growth unless a higher FC is maintained is another. By the way, at your pool's 80 ppm CYA, you should have an absolute minimum FC of 3.6 ppm at all times and I'd set it to 4 ppm FC to be safe. In a manually dosed pool, the minimum would be 6 ppm, but an SWG seems to do OK at a lower level, probably due to the superchlorination of the water that goes through the SWG cell. This all assumes you don't use an algaecide (e.g. PolyQuat 60) or a phosphate remover. You can always spend more money with regular use of an algaecide or phosphate remover and then use a lower chlorine level, but just keep in mind that chlorine alone can keep away algae -- that is, you don't have to spend more on these other products unless you want to. They are more like insurance in case the chlorine level drops too low.

There is another alternative for helping to reduce algae growth and that is to add 20 Mule Team Borax (plus acid since the Borax increases pH) to get to 50 ppm Borates. These act as an additional pH buffer and also as an algaecide, though not as powerful as PolyQuat 60. That lets you cut down the SWG output as less chlorine is needed to prevent algae growth. The use of a phosphate remover has a similar effect -- lots of options, but some are more expensive than others (using chlorine alone is least expensive, then Borates, then PolyQuat 60 and finally phosphate removers).

This post describes the procedure for lowering the TA if you find that you need to add acid frequently to keep the pH down. Essentially this procedure just accelerates the process that your pool will be going through compressing months into days. At your pool's 80 ppm CYA level, you could target a TA as low as 70 ppm though you can lower the TA to 80 ppm and see how it goes. Right now, your pool is actually slightly over-saturated with calcium carbonate (the saturation index is +0.14) and with an SWG you want to be a little under-saturated because scale has a tendency to build up on the SWG plates (even with auto-reversing polarity, though that certainly helps reduce the problem). That's something else this pool store apparently was not aware of -- though they certainly were ready to sell you an Alkalinity increaser.

By the way, they basically just sold you Arm & Hammer Baking Soda which is Sodium Bicarbonate. So you should compare the price of what they sold you to what you can buy in a grocery store or Costco for a large box of Baking Soda. Is their "bulk" price really a good deal (you can generally get Baking Soda for around $1 per pound or less if you search the web $18-$20 for 24 1-pound boxes)? If this pool store were giving you good advice, then paying more for chemicals would be worth it, but so far I don't see where they have been really helping you -- yes, the phosphate remover is a quick (and expensive and profitable) way to get rid of algae (using a copper algaecide does that as well, but with side effects from the extra copper), but they haven't told you why you got the algae in the first place (too low an FC for your CYA level) and gave you incorrect advice regarding the TA level which may now be too high.

Richard
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Minimun Phosphate Levels ??

Postby AprilZer » Thu 04 Jun, 2009 05:24

Now I know it .,Thanks for sharing you ideas I am so glad that I am a member of this site.,


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