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Thread: Questions about Phosphate Chlorine and Algae

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    shane4's Avatar
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    Questions about Phosphate Chlorine and Algae

    Hi All

    I have been around numerous topics here and as usual, have received so much awesome information. I admit though that I am about to take the easy way by starting a new topic as the various posts I am reading are not getting the direct answer I was looking for. Sooooo, I apologise if this topic has been covered before.

    I don't treat phosphate as I learned here to kill the algae and not worry about it. However, 2 pool stores have told me high phosphate can hold on to, or interrupt FC. Is that accurate?

    MY CYA is high at about 100. FC has been holding around 20 for days despite hot and direct sun. Although not recommended, a CYA of 100 should have target FC of 12. I am at 20ish and water is clear but algae is just staring to form on one seam. I shocked a week ago to get rid of some algae and that is how FC got so high. I realise I may not have had the FC high enough for long enough to rid all the algae, but it has held high for days now and yet algae is starting again. I realise the CYA is high but my levels of FC should still work no?

    Is it high phosphate that could be interfering with the FC to keep the algae at bay????
    16' x 32' IG, vinyl, 80k litre (21k gal), "lazy L" (kidney like at deep, squared off at shallow) shallow 3', deep 8', Hayward sand filter 300 lbs, 20gal/min Mod S-244T, Pentair Superflow VS 1.5 HP Model 342001, Raypak Heater 266K BTU Mod P-R266A-EN-C, 2 returns, 1 skimmer, 1 main drain, diving board, Southern Ontario (Canada) climate.

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    Re: Questions about Phosphate Chlorine and Algae

    No. The 'standard' level of FC that the FC/CYA chart calls for is more than enough to keep algae at bay regardless of the level of any other nutrient.
    When you said you 'shocked' what do you mean by that?
    Bob - Palm Beach by San Juan Pools. approx 5000 gals., Pentair 320 cartridge filter (all new guts installed by me), Goldline SWG, 'New to me' Kreepy Krauly Sand Shark, Intermec 104 Timer Test kit: TF-100 w/Speed Stir

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    Re: Questions about Phosphate Chlorine and Algae

    Phosphate does NOT interfere with FC levels. They are independent chemically. Chlorine does not react with the phosphate compounds that are removed by PhosFree type products. Phosphate is simply food for algae but if you maintain sufficient chlorine levels, there's no algae to eat the food. Pool stores will tell you lots of things to sell you liquid gold phosphate removers.

    While your CYA is higher than recommended, maintaining an FC minimum of 7.5% of your CYA level is enough to kill and keep algae away. That is, at 100 ppm CYA, 7-12 FC is enough. Are you certain that you have algae forming and not just dust settling in the seam? Have you performed an overnight chlorine loss test to confirm something is growing in your pool? That would tell you definitively if you had an algae issue. You may also have poor circulation in that area, allowing local FC levels there to get too low, a possibility with your pool shape.
    Joel - TFP Moderator - Minnesota - **Become a TFP Supporter!** Helpful Links: ABCs of Pool Water Chemistry - SLAM Procedure - Chlorine/CYA Chart
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    Re: Questions about Phosphate Chlorine and Algae

    No, the phosphate is not interfering with the FC, it is the high CYA that is interfering with the chlorine from doing its job.

    With a CYA level of 100 the shock level is 39 ppm of FC, so even with the FC at 20 you are still not at shock level. Getting rid of algae isn't a one or two time shock, it should be eliminated with the SLAM Process, see my signature.

    When CYA measures 100 it could very well be above 100 as that is the max that most reliable CYA tests can read.
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    Re: Questions about Phosphate Chlorine and Algae

    Quote Originally Posted by pabeader View Post
    When you said you 'shocked' what do you mean by that?
    I added liquid chlorine to my pool. The pool store suggests their bulk liquid is 12.5%. I kept a previous label from a jug of 10.3% that suggested 16 liters for my pool for visible algae. I put 16 liters of the bulk so called 12.5% which skyrocketed the FC (never got the measurement). Even though I only saw a bit of algae the water was crystal clear before shocking. The next day there was LOTS dead stuff on the bottom so that goes to show it's there even if you don't see it. The day after that a little more. Since then no issues. But a week later a little is starting again and the bottom of my pool will raise a cloud of debris when I run my cleaning brush across it. So I know the algae probably never left as I only shocked, not slammed.

    I just wasn't sure why the FC stayed so high for the entire week. Nothing has been added and the FC as of now is down to about 17ppm. Still high enough for my CYA. I was puzzled as to why the FC did not keep the algae at bay. Totally clear and then a week later its coming back.

    When two stores told me it was phosphate interfering with the FC I was skeptical. But wanted to check here.

    As I thought, phosphate will feed algae but wont "hold back" or "use up" FC. In other words, phosphate has nothing to do with the held high levels of FC. Right?

    So I assume the high CYA is why my FC stayed high for so long???

    And I shocked when I should have slammed........ right?

    As for my CYA, the pool season here is done in a few weeks so I don't really want to drain some water and refill only to drain again for closing. I dont want to keep putting in too much chlorine either as the FC stays so high for so long and don't want to disintegrate my kids for their last few swimming weeks.

    I should be in Florida this Xmas so hopefully I can get a TF100 sent to where I will be and be able to control my own tests. They cant ship them to Canada and Taylor Kits here are stupid expensive. I Will also try liquid chlorine or bleach next year well and say good bye to CYA raising pucks !!!!!

    I guess I should be slamming?????

    For the next few weeks, any other suggestions? I will check flow around the pool. Maybe the jets/eyes can be adjusted.
    16' x 32' IG, vinyl, 80k litre (21k gal), "lazy L" (kidney like at deep, squared off at shallow) shallow 3', deep 8', Hayward sand filter 300 lbs, 20gal/min Mod S-244T, Pentair Superflow VS 1.5 HP Model 342001, Raypak Heater 266K BTU Mod P-R266A-EN-C, 2 returns, 1 skimmer, 1 main drain, diving board, Southern Ontario (Canada) climate.

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    Re: Questions about Phosphate Chlorine and Algae

    Hi Shane,
    THe phosphates dont interrupt FC. But if you have algae, then the phosphates are not helping the situation.

    To explain it all isnt the easiest thing to do but I will try to keep it simple.

    If you are algae free then the recommended FC level will hold algae spores that come into all of our pools every day and prevent it from multiplying = nice clear pool no matter what the phosphate level.

    However if you have enough algae to be visible or to consume your FC quickly, the the recomended minimum isnt quite sufficent, and that is feeding from the phosphates.

    It takes FC of 40% of your CYA in order to kill algae faster than it can multiply regardless of the phosphate level. Thats why with even FC of 20, its continuing. Algae multiplies every 6 hours and its the 40% rule that brings fC to a sufficient level to prohibit the quick multiplication of it.

    So if you have algae + high nutrient level, + insufficinet FC of < 40% of CYA, then the algae will continue to bloom on you.

    You need to remember, that the TFP method and pool store method are two entirely different philosophies of pool care, so you are going to get entirely different answers to your questoins from the pool store, and from TFP. But remember, TFP is based upon factual science, and not some
    salesmans slick pitch without anything to back it up.






    Quote Originally Posted by shane4 View Post
    Hi All

    I have been around numerous topics here and as usual, have received so much awesome information. I admit though that I am about to take the easy way by starting a new topic as the various posts I am reading are not getting the direct answer I was looking for. Sooooo, I apologise if this topic has been covered before.

    I don't treat phosphate as I learned here to kill the algae and not worry about it. However, 2 pool stores have told me high phosphate can hold on to, or interrupt FC. Is that accurate?

    MY CYA is high at about 100. FC has been holding around 20 for days despite hot and direct sun. Although not recommended, a CYA of 100 should have target FC of 12. I am at 20ish and water is clear but algae is just staring to form on one seam. I shocked a week ago to get rid of some algae and that is how FC got so high. I realise I may not have had the FC high enough for long enough to rid all the algae, but it has held high for days now and yet algae is starting again. I realise the CYA is high but my levels of FC should still work no?

    Is it high phosphate that could be interfering with the FC to keep the algae at bay????
    Divin Dave,
    IG Vinyl, 15' x 30', 3 1/2' - 6' deep, Oval, ~15K gal, Intelliclor IC40, Intelliflo VS pump, Clean and Clear 420 Filter, auto-fill-disabled, Retrofit LED Color Light, Dolphin Nautilus Robot, TF100 Test Kit, Taylor K1766 Salt Test Kit, Tftestkit Pressure Gauge.
    www.tftestkits.net Experience- it's what's learned just after you needed it most !!

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    Re: Questions about Phosphate Chlorine and Algae

    What kit are you using to test FC levels over 10 and cya levels of (at least) 10

    edit: Ok, saw that you're singing it a bit without a good kit. This is how life with a pool will be until you get accurate test results.
    10,500 gal IG, Topaz Pebble, auto-level
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    Re: Questions about Phosphate Chlorine and Algae

    I am using the Taylor K 1004 and for CYA I go to a pool store that uses a complete Taylor kit (not sure of the model) but they can do the CYA test and some of the salespeople actually know how to use it !

    ok, so I understand that even though the FC was high enough to control algae but not high enough to eradicate it.

    And so, is the high CYA why the FC stayed around 20 for a week despite algae in the pool and direct sun?
    16' x 32' IG, vinyl, 80k litre (21k gal), "lazy L" (kidney like at deep, squared off at shallow) shallow 3', deep 8', Hayward sand filter 300 lbs, 20gal/min Mod S-244T, Pentair Superflow VS 1.5 HP Model 342001, Raypak Heater 266K BTU Mod P-R266A-EN-C, 2 returns, 1 skimmer, 1 main drain, diving board, Southern Ontario (Canada) climate.

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    Re: Questions about Phosphate Chlorine and Algae

    I would get your own proper test kit and test the CYA yourself. 100 ppm sound suspiciously like "100+" and calling it 100.

    If you are using the Taylor K-1004, then how can you be testing for 20 ppm FC? You'd need a FAS-DPD test kit to measure that high.

    Until you get your own proper test kit, either the TFTestkits TF-100 or the Taylor K-2006, then I don't think there's much point speculating about what is going on since we don't really know the true FC and CYA levels in this pool.

    In the meantime, I'd suggest brushing the area where algae is forming to stir it up and get circulation in the area. You should also make sure it isn't pollen.
    16,000 gallon outdoor in-ground 16'x32' plaster pool; Pentair Intelliflo VF pump; Pentair IntelliTouch i9+3s control system; Jandy CL-340 square foot cartridge filter
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    Re: Questions about Phosphate Chlorine and Algae

    Thanks Chem Geek But as mentioned, TF100 is not available to me and I am aware of the need of a good test kit.

    Just to clarify, my question was not specific to measured levels but rather would high CYA be responsible for holding FC at elevated levels for days despite direct sunlight and adding no other chlorine product. I guess I should have worded my question differently. If CYA is high (regardless of level) can it hold FC for long periods of time? I see chlorine burn up in a day with low CYA, so I was wondering how strong can CYA really hold on to FC. If it were 100+ would one expect to see FC hang around for a day or two, days on end, a week???

    With my K1004 I use Taylor's high chlorine test block so I can measure up to 20. Well actually 20 "ish" as the block only gives a range as opposed to FAS. As mentioned I utilise the pool stores Taylor set as well which is full range (don't know the model number) for tests I can not do at home.
    16' x 32' IG, vinyl, 80k litre (21k gal), "lazy L" (kidney like at deep, squared off at shallow) shallow 3', deep 8', Hayward sand filter 300 lbs, 20gal/min Mod S-244T, Pentair Superflow VS 1.5 HP Model 342001, Raypak Heater 266K BTU Mod P-R266A-EN-C, 2 returns, 1 skimmer, 1 main drain, diving board, Southern Ontario (Canada) climate.

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    Re: Questions about Phosphate Chlorine and Algae

    Yes a very high CYA level would maintain the FC level higher in spite of sunlight, but I don't think your FC is as high as you are measuring and I think your CYA may be much much higher. Remember that with Trichlor pucks, for every 10 ppm FC they also increase CYA by 6 ppm. Also, if you've been using Dichlor granulating chlorine as a "shock" product, for every 10 ppm FC it also increases CYA by 9 ppm.

    It's possible that your FC is actually closer to 10 ppm and that your CYA is over 200 ppm. That would explain the slower FC drop and the presence of algae growth especially in areas of poor circulation. But again, we are completely guessing here and I think it's pointless to speculate until you get a FAS-DPD test to accurately measure the chlorine level and a CYA test you can measure yourself to see how high it actually is.

    The high-range DPD comparator from Taylor is the 9056 and only reads to 10 ppm so your 20 ppm "guess" may be incorrect and you should note that DPD starts to bleach out at higher FC levels so that 20 ppm FC would probably show up as lighter than 10 ppm, not darker (so your reading is more likely to be closer to 10). To read even high ranges using a comparator, you'd need the 9297 for the OTO test though even that doesn't give you enough resolution to be precise.

    As for the pool store, you cannot generally trust them to do tests correctly. Depending on the type of test they are using, they may not be calibrating their instruments (if they use colorimeters) or cleaning their vials or waiting the right amount of time for tests or diluting to measure higher levels, etc. I doubt the pool store is using a FAS-DPD test for chlorine.
    16,000 gallon outdoor in-ground 16'x32' plaster pool; Pentair Intelliflo VF pump; Pentair IntelliTouch i9+3s control system; Jandy CL-340 square foot cartridge filter
    12 Fafco solar panels; Purex Triton PowerMax 250 natural gas heater (200,000 BTU/hr output); automatic electric pool safety cover; 4-wheel pressure-side "The Pool Cleaner"

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    Re: Questions about Phosphate Chlorine and Algae

    Hi Shane! What part of southern Ontario are you from?
    Just so you know, i have family in the Sarnia area who use some kind of postal shipping service in Port Huron to order things that don't ship to Canada

    If you're close to a border, you might want to look into those services, because even if you get the tft100 or Taylor kit shipped to you in FL, you'll periodically need to restock.

    Its tough to give you any good TFP advice when we know you're hamstrung kit-wise, but I will say that sooner or later you'll need to drain, possibly several times given that you've a liner and will only want to do partial drains,, to bring that cya down.

    So apart from having the pool out of play for a bit, there'd be no harm in doing a partial now just to get your effective slam FC rate into a more manageable range. Then drain some more on close.

    That said, I understand completely if the reason you don't want to drain right now is to squeeze every last swim outta the season
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    Re: Questions about Phosphate Chlorine and Algae

    Hi, Shane. Your initial post shows you have a good grasp of pool water chemistry.

    Your plight also points out how difficult it is to maintain a pool with high CYA.

    I would suggest you tackle the high CYA right now. Get it down to 40 or so in your climate.

    I know it may be too late to swim but I think you'll have a great opening if you harness your CYA and put in chlorine at first to SLAM (20 ppm) and then to winterize.
    Dave S.
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    Re: Questions about Phosphate Chlorine and Algae

    Thanks for the last few replies.

    I dont seem to get notifications of my threads even though I "subscribe". When I come to check these posts, I am not subscribed even though I did at my last entry. Anyone suggest what I may be doing wrong?

    Thanks Swampwoman but I have not heard of those services. And I am just outside Toronto so nowhere near Sarnia.
    I think the initial TF Kit will be good arriving in Florida and I bring it home. My uncle has a PO Box in NY State but I dont like bother him too much with items as big as the kit. But refill supplies should be smaller and easier for a PO Box. So hopefully next season I will be set.

    Duraleigh, after closing I should be losing about 18" of water to replace in the spring so hopefully that should help with the CYA. I replaced my liner two seasons ago. So at that time I technically started at 0 CYA. I had to add CYA into the initial water shipment to get started, After that, for two seasons I have be using stabilized pucks. When shocking I use liquid chlorine. Over the two seasons there has been one winter water level drop for closing and top up in spring (about 18" of water). There have been numerous 1" top ups with the garden hose over the two seasons for evaporation. And yet it only took the two seasons to build up that CYA to the FC lock I seem to be experiencing. I cant understand how a few friends of mine use pucks for years and never seem to have algae problems or high chlorine. I really like the convenience of pucks though I guess I will have to switch to liquid chlorine next season.

    Chem Geek, just for note, my test block does not seem to have a part number on it but it is a Taylor with the two top FC ranges of 7.5 to 15 and 10 to 20. It also has PH and CYA as well. I do not have the agents for the CYA but if I don't get a TF Kit I will at least get those agents. With a range of 10 to 20 I am definitely guesstimating by judging the darkness of that colour. Lighter must be closer to 10 and darker closer to 20. Ok how many of you just slapped your palm to your forehead???? hahahaha

    Like I said, not worrying now as I am getting ready to close. 11:30 pm right now and it's 12C outside (about 54F). This afternoon was not much better. We are getting a warm snap this week but today was a warning that the house furnace needs to be fired up soon. I dont run the furnace and the pool heater at the same time. $$$$$$$$$$$$$ Noooooo Waaaaay.

    Cheers!

    - - - Updated - - -

    correction it does appear that I have the 9056 High chlorine comparator block
    16' x 32' IG, vinyl, 80k litre (21k gal), "lazy L" (kidney like at deep, squared off at shallow) shallow 3', deep 8', Hayward sand filter 300 lbs, 20gal/min Mod S-244T, Pentair Superflow VS 1.5 HP Model 342001, Raypak Heater 266K BTU Mod P-R266A-EN-C, 2 returns, 1 skimmer, 1 main drain, diving board, Southern Ontario (Canada) climate.

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