phosphates...chemgeek, backglass are u out there.

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pooldad07

phosphates...chemgeek, backglass are u out there.

Postby pooldad07 » Sun 15 Jul, 2007 17:58

I finally thought i solved our green pool problem. Culprit was phosphates. We had a level of 750 and the pool store had me buy phosfree and for 9 days our pool was so clear I could read the date on a penny in the deep end :-) I was shocked at how much a pool could sparkle...Problem solved....Well 2 days ago we notice the green haze creep in and now I am fighting algae again and had water tested..phospahtes at 500 ppb. We have a tree/wooded pool area and we can only imagine the phophates are entering through the trees. This seems crazy cause our neigbor down the street has even more trees yet his is fine. Maybe its our large Pines??? Anyway I shocked for the 3rd time today. I went back to using bleach from the grocery store. After a day and a half our pool is still cloudy/green. I know the phophate chemical does not kill algae but takes away a key nutrient. Any help from one of the chemical guys on why I am getting high phosphates and their relationship to algae growth. All my other levels are perfect according to a good pool store. 30,000 gallon in ground liner with all new equp and sand filter using chlorine tabs....I think I may start ujsing algaecide which I thought if you maintain proper chlorine levels it was not needed.

thanks from pool dad...


chem geek
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Postby chem geek » Sun 15 Jul, 2007 19:18

What is your Cyanuric Acid (CYA) level and minimum Free Chlorine (FC) level? And yes, using a weekly maintenance dose of PolyQuat 60 algaecide will keep away algae even if the chlorine level gets to low. And yes, removing phosphates will prevent algae growth but does nothing to prevent additional phosphates from getting blown in via dirt and fertilizer, etc.
pooldad07

Postby pooldad07 » Sun 15 Jul, 2007 19:26

cya was 61. Free chlorine was very high the past 2 weeks (around 20-25) due to my constant shocking. When the pool turned crystal clear I waited for my free chlorine to dip below 10 before I did anything else. Now the algae is back so after my current shock it is probably back to 15-20...

My pool guy suggeested I add some DE to my filter for an extra line of defense....

thanks
chem geek
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Postby chem geek » Sun 15 Jul, 2007 19:57

So the FC level dropped to 10 (with your CYA of 61) and then the algae came back at that point, is that right? Did you measure the CYA yourself using a Taylor K-2006 test kit (a number of "61" sounds like a pool store measurement)?

The DE added to a sand filter will certainly filter better, but won't kill algae. You could use a weekly maintenance dose of PolyQuat 60 to do that or add 30-50 ppm Borates to the pool (or Copper, but that has side effects).

I think you should still test the water yourself. You may have more than 61 ppm CYA in it. In any event, you can certainly use the algaecide to keep algae away if you want and then won't have to worry so much about the chlorine or CYA levels.
pooldad07

Postby pooldad07 » Sun 15 Jul, 2007 23:25

You are correct in your last post about order of events. And yes 61 is my pool store number. I just dont know how the phosphates came back so fast so high. I guess I will start using algacide. I just dont know why I am getting algae when I follow all the levels and keep my chlorine high. I guess I assumed algacide is a band aid but not solving the problem. I would prefer to find the source of my algae..Phosphates? The reason I did not worry about CYA too much is that my pool is 1 year old and we closed last year by lowering water and added more to open this year. If I do the algacied should I continue a weekly maintence of the Phosfree??? So each friday nite i should shock, add Pokyquat 60 and Phosfree?

In the pool store there were 4 people behind me with water samples and algae problems....

Thanks
chem geek
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Postby chem geek » Mon 16 Jul, 2007 13:10

Though you can certainly use the weekly algaecide, I think you should also get yourself your own good test kit, the Taylor K-2006 kit you can get from Taylor here or from Leslie's here or the even better kit based on the Taylor one from tftestkits here .

Though mustard/yellow algae has needed about 15% of the CYA level to keep away, green algae has never needed more than 7.5% of the CYA level except with high phosphates (higher than yours) where it needed around the target 11.5% of CYA level. So either your pool has a new situation we should figure out or the testing numbers aren't right -- either the CYA or the FC.

If you wouldn't mind, before you go down the algaecide route if you would just keep your chlorine level up above when the algae occurs -- so just above 10 -- and get yourself one of the good test kits, then you can test the CYA and accurate FC numbers yourself. If you don't want to do this, I understand -- it would just be good to know if the numbers are real since pool stores do not always measure these things accurately. Depending on your initial CYA level and the amount of chlorine you added during the year and the amount of dilution (and backwashing) you did, the CYA could be higher though you are right that 60 does "sound" about right. But with every 1 ppm FC adding 0.6 ppm CYA from the tabs, just adding 2 ppm FC per day over 4 months adds 144 ppm CYA. Every 3" 8-ounce chlorine tab added to your 30,000 gallon pool raises adds 1.8 ppm FC but also adds 1.1 ppm CYA. So if you used 100 tabs, you added 110 ppm CYA. With regular backwashing of a sand filter, that can get cut down, but your large pool size makes this backwashing amount a smaller fraction of total water volume so the dilution is not as much.

Richard
pooldad07

Postby pooldad07 » Tue 17 Jul, 2007 17:16

I will get a test kit by the end of summer. I knoiw the 60 CYA should be accurate cause 3 diff people have tested with basically the same numbers. Today the pool loks very good. It does not sparkler like last week but I will take it over a green pool. It just seems to have a slight grey haze. I have kept hte FC pretty high the past few days and added the phosfree 2 days ago.

I am going to start friday nite with a new routine. Just let me know how many bags of shock you would add to a 30k gallon in ground pool. I usually shock with 2 bags but maybe i should do more each week..This week I want to shock with 2 bags and do a maintance amout of phosfree at the same time. Any other shock schedule you think I should follow?

Thanks
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Postby chem geek » Tue 17 Jul, 2007 17:33

What are you using for shocking the pool? Is it Cal-Hypo? If so, then for every 1 ppm FC you add, you also add 0.7 ppm to Calcium Hardness (CH). If you maintain chlorine levels and have the pool exposed to sunlight at least part of the time, then you usually do not need to shock the pool. Organics will get broken down continually.

When you get your good test kit you will be able to explicitly measure Combined Chlorine (CC) and should find it almost always < 0.5 ppm which means you don't need to shock the pool. The only other time to shock is when algae develops -- the pool will get hazy or cloudy when that happens. The fact that your pool is still not clear means that you still have algae growth and it will be consuming your chlorine quickly. I suspect that though you may add enough chlorine to get to some FC level, if it ever drops too low then the algae will come back. When you get your own good test kit, you'll be able to accurately measure the FC level to within 0.2 ppm though it also can test within 0.5 ppm when you have higher chlorine levels (it uses less reagent that way).

Until your pool is crystal clear, I would keep the Free Chlorine level high, though without a full set of numbers it's hard to know whether your other numbers (pH, TA, CH) are such that your pool is over-saturated in calcium carbonate. Adding Cal-Hypo would just cloud up the pool in that case.

Richard
pool tech

phosphates

Postby pool tech » Sat 04 Aug, 2007 04:04

It is possible you needed 2 treatments of phosphate remover to begin with. The phosphate remover usually sold at pool stores like leslies is nt very good. I only use SEAKLEAR Zero phos phosphate remover it's the best. Check your surrounding pool area for water runoff from flowerbeds and such and also if you have a dog that swims you will get phosphates rappidly. Also get your cya up to 80ppm

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