Phosphate, Algae Continuum!

Algae problems in swimming pool water.
Green (cloudy) water or slimy pool walls.
Black algae. Mustard algae. Pink or white pool mold.
poolo
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Joined: Thu 08 Jul, 2010 15:25
My Pool: 23,000 GAL GUNITE POOL. 48 SQ FT SAND FILTER. WHISPERFLO 1HP PUMP
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Phosphate, Algae Continuum!

Postby poolo » Thu 08 Jul, 2010 16:54

Okay all of you pool experts I need help!
I am in a blackhole continum. We have city water with phosphates added. So when I go to top off the pool phosphate go in. We just moved into the home we are renting. The pool was not really maintained well. I am now in a vicous circle. Phosphate high = algae. So we used SeaKlear Phospate remover then vacuumed to waste the next day...well when you vacuum to waste we all know what happens it take LOTS of h2o our while you're trying to get rid of the algae. SO then we have to add H20...= more phosphates.
And on and on and on. The landlord had someone come and fix the filter pump timer today and he looked over the rest of the equipment and backwashed and rinsed and now again, pool is low on water and needs more h20 and up the phosphates will go.........
It is eating up lots of cholrine and is constantly cloudy...
I hand it over to all of you...
the pool store is great and they have given us lots of free stuff and advice (they are not robbing us) I checked prices....but the phosphate remover we used once is WAY expensive and the thought of needing it again is sickening since I know I will have to vacuum to waste and then add more phosphate ridden H20...needless to say I do not even want to see my waterbill this month.


chem geek
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Phosphate, Algae Continuum!

Postby chem geek » Thu 08 Jul, 2010 21:49

Phosphates (and nitrates) are irrelevant if you maintain an appropriate Free Chlorine (FC) level relative to your Cyanuric Acid (CYA) level. I have over 3000 ppb phosphates in my pool (shown here and here ) and 400 ppb in my fill water yet maintain it algae free using chlorine alone. Read the Pool School for more info on how you can properly maintain your pool. First step is to get a good test kit and there's an article on that as well -- you can get either the Taylor K-2006 or the TF-100 .
AB_Ethan

Phosphate, Algae Continuum!

Postby AB_Ethan » Tue 13 Jul, 2010 19:23

That is a waste of chlorine and stabilizer, lol. Ideally, get rid of the phosphates as it acts as a steroid for algae Pick up some NO PHOS or other brand of Phosphate remover, as well as chlorine and clarifier. You could have high chlorine and stablizer and still have cloudy water because of phosphates.
chem geek
Pool Industry Leader
Pool Industry Leader
Posts: 2382
Joined: Thu 21 Jun, 2007 21:27
Location: San Rafael, California

Phosphate, Algae Continuum!

Postby chem geek » Wed 14 Jul, 2010 12:00

There are over 15,000 members at Trouble Free Pool and historically over 20,000 members at The PoolForum who would disagree with you. Yes, phosphates (and nitrates) are food for algae so accelerate their growth, BUT that growth rate is also limited by sunlight and temperature so that no matter how many algal nutrients that are provided, their growth rate isn't faster than doubling in 3-8 hours. If the active chlorine level is high enough to kill algae faster than they can reproduce, then algae will not grow, period. The active chlorine level is related to the FC/CYA ratio which is why one must know both -- FC alone is irrlevant since CYA significantly lowers the active chlorine (hypochlorous acid) level that kills algae.

Phosphates and nitrates are like wood for a fire -- they are fuel -- but if there is no flame, then the amount of wood (i.e. algal nutrients) is irrelevant and chlorine acts to douse out any spark before a flame gets started, IF the FC/CYA ratio is sufficiently high where the FC is at least 7.5% of the CYA level in manually dosed pools or at least 5% of the CYA level in saltwater chlorine generator (SWG) pools. So long as the chlorine does not get below the minimum levels, algae will be killed faster than it can reproduce so there will be no cloudiness or unusual chlorine demand from algae growth. If you've already got nascent algae growth because the FC/CYA ratio got too low at some point, then you need to shock the pool to a higher active chlorine level to kill off the algae quickly, but once killed off then the minimum FC/CYA ratio will keep the algae from growing by killing it off before it is able to reproduce.

Of course, you can certainly spend more money to remove phosphates just as you can for using algaecides, but it isn't necessary. Also note that phosphate removers only remove inorganic orthophosphate and do not remove organic phosphates that algae can also use for food, though the uptake of organic phosphates is slower. So it can help take the edge off of algae growth, but does not completely eliminate it in all situations. Sufficient active chlorine levels, however, will stop algae growth.

The following are chemical rules of fact that are independent of concentration of product or of pool size:

For every 10 ppm Free Chlorine (FC) added by Trichlor, it also increases Cyanuric Acid (CYA) by 6 ppm.
For every 10 ppm FC added by Dichlor, it also increases CYA by 9 ppm.
For every 10 ppm FC added by Cal-Hypo, it also increases Calcium Hardness (CH) by at least 7 ppm.

So even with a low 1 ppm FC per day chlorine usage, continued use of Trichlor tabs/pucks adds over 100 ppm CYA in 6 months if there is no water dilution. So it is easy to get the FC/CYA ratio too low and for algae to start growing when using stabilized chlorine products. One can learn more about how to maintain their pool easily and inexpensively by reading the Pool School .

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