Phosphates/algae/chlorine

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D

Dazed_N_Confused

0
Jun 17, 2007
9
Arizona
What it is: Fiberglass in-ground pool, 5,100 gallons, cartridge filters, located in Arizona

Problems: reoccuring mustard algae, phosphate level off the chart, disappearing chlorine

What's been done: shock, clean filters, shock, clean filters, phosfree (R), shock, clean filters

Result: Chlorine level barely registers & will be gone in another couple of hours and the phosphate level is still over 20,000.

As I understand it, to prevent algae you maintain optimum sanitizer level and eliminate "food" for algae. Algae eat phosphates and according to the levels in my pool, I'm running an "All-You-Can-Eat" algae buffet.

Questions: 1. How can I fix this? 2. How can I keep it from happening again?

I'd appreciate any advice or guidance to help me change this water-filled chemical pit back into a nice little play pool.

Thanks.
 
We need a full set of test numbers to give you specific advice.

In general, you will need to bring the chlorine level up quite high and hold it there for several days to get right of the algae. Exactly how high the chlorine needs to go depends on your CYA level.

Phosphates are not normally an issue at all. There is all kinds of marketing hype around this issue designed to sell products you don't need. If you keep the chlorine at appropriate levels you won't get algae. In extreme situations there are some exceptions to the is general rule. Your phosphate level is very high and that could cause additional problems. I wouldn't worry about that though until you try getting your chlorine level high enough and holding it there for several days and see if that does it.
 
20,000 ppb of phosphates? I'm wondering how they could get this high. I'd consider having my fill water tested for contamination of phosphates.

I think you should simultaneously treat for high phosphates as well as shock but with that high of a level it may be so costly to remove phosphates. Phosphate removers are expensive and according to the SeaKlear Phosphate Remover specs it would take at least 5 bottles to clear up your size of pool with 20K ppb and probably lots of backwashing time. Plus clarifier costs, if you are in a hurry to clear up your pool cloudiness from the treatment. Also, at that high level you will most likely see faster recurrences of algae. In this case, I'd seriously consider dumping and refilling most or all of the water. You are in for a ton of time and money trying to treat that level of phosphates, IMO. I've never used a Phosphate floc but perhaps that might work, but I doubt it. I think by the time you vacuum it to waste, you'd end up refilling your pool. It's a catch 22. If your water costs are high, you may want to try treat, if they are lower, dump and refill. In my area, to fill a 15K gal pool costs about $100, so I'd dump.

Once your pool is cleared up, since your levels get this high, you may be a candidate who does need to use an ounce or so of phosphate remover once a week.
 
Thanks for the quick response!
Here's the numbers: FAC = 0; TAC = 0; pH = 7.4; TA = 120; CH = 400; CYA = 100; TDS = 2,000; phosphates > 2,500 ppb.
I've put 2# of shock a day for the past 4 days and still no chlorine after 6 to 8 hours. I have pucks in the skimmer and floater full open. The visable algae has been gone since the initial brush/shock/brush/clean filter cycle.
Do I have to wait till evening to put in shock or can I do it anytime?
Thanks for the help.

As I review the last 2 test reports, one says Phosphates > 2,500 and the other says > 20,000. That is a huge variance, and I need to have it retested to get clarification. I'll repost numbers in about an hour or so.
 
You should bring your chlorine level back up to 25 as frequently as possible, every two or three hours if you can manage it. If you leave it low for too long the algae will start growing and slow the whole process down significantly. You want to keep doing this until your FC level holds overnight. While that is happening you should also brush the pool once a day and backwash/clean the filter every second or third day or whenever the pressure goes up 10 lbs.

What kind of "shock" are you using? Different ones have different issues with them. You should think about switching to bleach for chlorine instead of pucks and powdered shock. The pucks, while easy to use, add CYA and your CYA level is already on the high side. The powdered shock also adds things you don't want, though probably not as troublesome as the CYA from the pucks it will still build up over time and eventually cause problems.
 
New Test Results
Store #1 - FAC = 0; TAC = 0; pH = 7.4; TA = 120; CH = 450; CYA = 50; Phosphates >2,500ppb
Store #2 - FAC = 0; TAC = 0; pH = 7.6; TA = 120; CH = 400; CYA = 30; Phosphates >2,500 ppb
Me - FAC = 0; TAC = 0; pH = 7.4; TA = 120; CH = 450; CYA = 100, no phosphate test

Had the same water sample tested at 2 different places/chain stores. The consensus is the phosphates are over 2,500 ppb, but neither place could tell exactly how far over. The place that initially told me 20K is not open on Sundays (?)

For pucks I'm using HTH 3n1, 47.6% Cal Hypo, shock is Leslie's Power Powder Plus, 73% Cal Hypo as well.

Question: My tester doesn't register above 10 for chlorine, how much chlorine/shock will I need to add to get it up to 25?

This is my first visit to this site, and a fantastic site it is! I printed out the info about the BBB method and need to read up on it, sounds like the way to go.

For now, I will bring the chlorine up, since I have a bottle of the PhosFree left (101 oz.) should I put it in after I get the chlorine up? I can't drain the pool till I get a pump (maybe Wednesday) so just use up the remaining chlorine I have and then switch to bleach?

Thanks for all the help!!!!
 
You can test higher chlorine levels by diluting your pool water with distilled water and then testing that. You can dilute one part pool water with one part distilled water and multiply the result by two or dislute one part pool water with two parts distilled water and multiply the result by three. The results are somewhat less accurate, but usable for this purpose.

2 lbs of cal-hypo 48% or 1 1/2 lbs of cal-hypo 73% will raise your chlorine level by about 25.

Cal-hypo adds calcium. Your calcium levels are already fairly high. You can afford to go a bit higher on CH, perhaps to 500, but at some point you are going to either need to stop adding calcium or replace some of your water to get the calcium levels down.

The PhosFree will get rid of some of the phosphates and it will cause your water to turn cloudy for several days. I don't think it is going to make any difference to the algae, particuarly as one bottle isn't going to make that much of a dent in a level of 25,000.
 
In theory, once algae have a full amount of the nutrition they need to grow from sunlight (photosynthesis), water, carbonates, nitrates and phosphates, then they can grow at their optimal maximum rate, but that is still a generation time (doubling of population) of around 4 hours in the case of algae. Maintaining proper chlorine levels should, in theory, keep the algae from growing, but there was a report from one other user (I think on this forum) who said that even going by Ben's chart didn't work in his pool with high phosphates so it would be interesting to see if that is the case in your situation as well. Other users with high phosphates (including waterbear) report no such problems with keeping away algae using chlorine alone (that is, before he added Borates recently, but before that he didn't report problems with algae even with high phosphate levels). Unless the phosphates are doing something to directly reduce disinfecting chlorine levels (either directly reducing chlorine or forming other compounds with chlorine, similar to CYA), then I don't see how the high phosphates are a problem.

We do know that yellow/mustard algae does need a higher chlorine level to keep it away -- closer to the Max level in Ben's chart or around the 0.07 ppm disinfecting chlorine level (column) in this chart. Shocking also requires higher levels corresponding to the 0.7 column in that same chart, assuming one lowers the pH first to 7.2 before adding the chlorine.

Quite frankly, if your CYA level is really close to 100 as you measured it, then that is MUCH more likely to be the issue than the phosphates since it is doubtful you kept the chlorine levels high enough for that CYA level to keep away algae (of any kind). However, if you are using test strips for CYA measurement, they are not accurate. Get a good test kit such as the one at http://www.tftestkits.com/.

Richard
 
Your chlorine is dispppearing becaese of the algae. The phosphates might or might not be a problem but most likely is NOT. (my pool has between 2000-3000 ppb and has never had an algae bloom!) I suspect that your have been maintaining your FC too low for your CYA. IF your CYA is truely beween 30-50 ppm you need to maintain a FC of 3-5 ppm for normal sanitation and algae control. Youi need to get your clorine levels up AND KEEP THEM THERE by testing and adding chlorine AT LEAST 2 times a day (3 or more is even better). IF you can get liquid chlorine or laundry bleach this will be the least expensive since you are going to need a LOT! Get your FC up to 25-30 PPM and KEEP IT THERE as best as possible until the FC is holding overnight. IT might take a few days to a week to acccomplish this.


IF your CYA is at 100 ppm (and I suspect that it might be) then you need maintian FC levels of 8-12 ppm FOR NORMAL SANITATION and shock to 25 ppm!

Have you added any mustard algae treatments to your pool? If you have and they are sodium bromide based then this would also explain why you cannot hold chlorine. These will convert your pool temporarily to a bromine pool and bromine cannot be stabilzied against UV light.

Forget the phosfree for now. Even if you get rid of all the phosphates in your water I will bet that there are nitrates present since you have a current algae bloom. Nitrates are the primary algae food and if they are present you can have 0 ppb phosphates and STILL get algae!

Finally, if you are using test strips to test your water they are not precise and your results cannot be trusted. Get yourself a good test kit such as the one offered on this site (or get a Taylor K-2006, not a K-2005)
 

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Well, I didn’t see waterbear’s post about “forget the phosfree” before I added what I had left so I don’t know what readings would have been if no more phosfree, but here are today’s results.


Early Test results
Mine (Taylor drop kit): FC = 18, TC = 18, pH = 7.2, TA = 130, CH = 480, CYA = 90
Mine (hth 6 n 1): TH = 400, FC = 15, pH = 7.2, TA = 120, CYA = 100

Added 1 gal 6% bleach

Mid-Day Test Results
Mine (Taylor drop kit): FC = 15, TC = 15, pH = 7.2, TA = 130, CH = 480, CYA = 90
Store #1: Saturation Index = .3, CYA = 88, TC = 10, FC = 9.6, pH = 7.6, TA = 114, Adj. TA = 88, TH = 390, Phosphates = 800
Store #2: FC = 7, TC = 7, pH = 7.4, TA = 120, CH = 400, Phosphates = 500

Floor of pool is covered in light grey “dust monsters”. Could this be the phosphates in a congealed form?

Pressure has increased 14 psi in 22 hours since I cleaned cartridges (16 psi to 30 psi)

I plan to quickly vacuum out the dust monsters and then clean the filters (since I can’t vac to waste), add more bleach and continue testing. Anything else I should be paying attention to? BTW, the pool is quite clear, considering all the stuff I’ve put into it.

I will be trying to learn as much as I can about these issues, but for now I think getting a TFP test kit is a “must have”.

By following the advice here, I just might be able to take care of this pool correctly, what a fantastic forum. Thanks to all!
 
Waterbear is right, it is the algae and not anything else that is really using all of your chlorine. I would take the chlorine level up to 25 and keep it there till all of the algae is dead, then give it a day or two more to really toast the buggers :evil: You want to get rid of it once and for all so that it doesn't keep coming back. Fiberglass can take really high levels of chlorine :-D If it isn't too expensive for you I really would suggest you drain the pool 1/3 and refill a couple of times till you get your cya down to 40 and your calcium down to 200 - 250. your alkallinity ison the high for a fiberglass pool too. It will be much easier to maintain your pool with the lower numbers. The stuff on the bottome is dead algae :)
 
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