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Thread: Algae - sand filter too old?

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    Algae - sand filter too old?

    Hi.
    I have been fighting algae since I can remember. The water in my pool is almost never sparkling and fully transparent. Is it possible that my sand filter just first do the job properly?
    I cleaned it up a few days ago (garden hose from the top) and there was lots of **** coming out. I had to keep cleaning it for like an hour. I put my arms in and messed the sand as deep as I could reach and I allowed the water from the hose stir it. Even after an hour water wasn't totally clean but was much better.
    Since then the pump has been running 24/7 for 3 days while I'm shocking the pool.
    What worries me is that the pressure on the filter hasn't changed at all. It started at 12psi after cleaning and 3 days later is still shows 12. I even replaced my old gouge (at the same time I cleaned the filter) as I thought that the old one was faulty (I don't think it ever showed some higher pressure). Water is a bit better and there is no residue at the bottom so it does filter something. I have also added a blue cube to the skimmer that is supposed to glue small particles together to help filtration. After 3 days I can barely see bottom at the deep end.
    1. Should the pressure increase after 4 days of shock?
    2. Is 12 psi normal sand filter pressure?
    3. How much sand should be in the filter? Mine is more than half full. I can reach sand from the top but need to stick my arms up to the elbows to do so.

    One more question .
    Every time I add chlorine - cal hypo 65% diluted in water - to the pool, the water gets instantly milky white. Is it normal? Does it mean I still have lots of algae? This morning I was able to see the bottom (just), added 500g of cal hypo to get to the shock level (16) and the pool is much more cloudy. Cannot see the bottom any more. Is it normal? Or maybe it reacts with something in the water?

    Appreciate any help. I'm dispirited by my never ending battle with the algae.
    Pawel.


    16000 gallons, SWG, IG/concrete, sand filter, the pool is 20+ years old probably

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    pwrstrk's Avatar
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    Algae - sand filter too old?

    It sounds to me like your not maintaining proper FC levels for your CYA level. If you have algae you need to perform the SLAM process. pool-school/shocking_your_pool.
    Take a look at this chart pool-school/chlorine_cya_chart_shock

    Can post a full set of test results and how you got them. This will tell us the story as to better guide you.
    I believe the cal- hypo can cloud the water.
    I don't believe your filter is the problem, as the pool water chemistry is probably out of balance.
    Jeff
    24'x54" AG Morada RTR (by wilbar) 13'500 gal. Hayward Powerflo Matrix 1hp 2 speed. Hayward Perflex EC65 DE filter.

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    Smykowski's Avatar
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    Re: Algae - sand filter too old?

    pwrstrk has you covered. Algae is almost always a balance problem, not a filter problem. The best thing you can do for your pool is get a good test kit and post your results here. Read Pool School over and over while you're waiting.

    Continually adding calhypo as your chlorine source might be problematic, and we usually suggest using plain old liquid chlorine for SLAMing. We'll be able to tell you more once we see test results.
    33' round, 23,000 gal AG vinyl , 1HP 2spd PowerFlo Matrix downsized with 3/4HP impeller (X2), Hayward S180T 150# sand filter (X2), Hayward H250 NG heater Pool Store year 1 - $850 for 2 months; Pool Store year 2 - $440 for 2 months, TFPC year 1 - $170 for 4 months; TFPC year 2 - $95 for 4.5 months
    The most important article on this site - The ABCs of Pool Water Chemistry

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    Re: Algae - sand filter too old?

    Welcome to the forum.
    I'm dispirited by my never ending battle with the algae.
    Don't be....there's not a quick fix but we can help you by changing the way you manage your pool water chemistry. It is almost never a fault of your filter.

    I would suggest you start by reading "The ABC's of Pool Water Chemistry" up in Pool School. That'll give you some idea of the basics and then next we'll need a set of test results.

    If you don't have a test kit that tests the parameters (from Pool School) you'll need to get one in the future. I see you are in Australia, so if you are lacking a good kit, for now, take a sample to the pool store for testing but don't buy anything. Post those test results and we'll get you started.

    You will need LOTS of household bleach to chlorinate, some patience and a willingness to learn but you have 24/7 tech support here on the forum.

    Stop using the Cal hypo. That is, in fact, what is turning your pool milky. It'll go away in a day or so but don't reuse it......you can use liquid bleach instead.
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

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    Re: Algae - sand filter too old?

    hi,
    Just to clarify - I do maintain proper FC levels for my CYA. I have TF100 test kit and I follow all procedures outlined here. I have been following this forum for a few years.
    FC - 16 is the level I need to shock at the moment (CYA around 30-40). I started shock with PH 7.5
    Chlorine level in the pool is never lower than 5, PH is always below 7.8 - do check them regularly.
    After last shock a month ago the water was not bad. Pool was mostly covered. Once uncovered I had green algae at the bottom (first time ever - it usually grows on the walls first). The balance of the pool was ok all the time. The water was clear. Once I brushed the algae the water got totally cloudy and I started the shock again. Normally the pump runs 8h a day at least. Because I maintain the balance all the time and still get algae I'm trying to find the problem. If it is not the filter I'm not sure what I can do make it better.
    I use cal-hypo only for shock (SWG) as this is the cheapest and most popular chlorine available here. Household chlorine is more expensive than the one from the pool shops (bunnings) or maybe I don't know where to get the cheap one. I will switch to the liquid one from now on. Thanks for the advice on that.
    16000 gallons, SWG, IG/concrete, sand filter, the pool is 20+ years old probably

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    pwrstrk's Avatar
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    Re: Algae - sand filter too old?

    The only way I know of algae forming is the FC levels have dropped below the minimum for the CYA.
    You may have gotten an algae outbreak at some point and never have gotten it cleared up totally.
    For the SLAM process to completely get rid of the algae you need to pass three tests for it to be done.
    1 water is crystal clear.
    2 pass the OCLT test.
    3 you have CC of 0.5 or less.
    Jeff
    24'x54" AG Morada RTR (by wilbar) 13'500 gal. Hayward Powerflo Matrix 1hp 2 speed. Hayward Perflex EC65 DE filter.

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    Smykowski's Avatar
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    Re: Algae - sand filter too old?

    If you are SLAMing multiple times, then either the FC is too low for the CYA level, or the algae was never totally cleared up in the first place.

    TFP recommended levels assume the water is clean and clear. If you have algae in the pool, and only use the maintenance FC/CYA ratio, you will never get rid of algae. It sounds like the SLAM was never completed correctly in the first place.
    33' round, 23,000 gal AG vinyl , 1HP 2spd PowerFlo Matrix downsized with 3/4HP impeller (X2), Hayward S180T 150# sand filter (X2), Hayward H250 NG heater Pool Store year 1 - $850 for 2 months; Pool Store year 2 - $440 for 2 months, TFPC year 1 - $170 for 4 months; TFPC year 2 - $95 for 4.5 months
    The most important article on this site - The ABCs of Pool Water Chemistry

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    Re: Algae - sand filter too old?

    Quote Originally Posted by pwrstrk
    The only way I know of algae forming is the FC levels have dropped below the minimum for the CYA.
    You may have gotten an algae outbreak at some point and never have gotten it cleared up totally.
    For the SLAM process to completely get rid of the algae you need to pass three tests for it to be done.
    1 water is crystal clear.
    2 pass the OCLT test.
    3 you have CC of 0.5 or less.
    I have been there and done that (I'm in the middle of that process again). thanks.
    16000 gallons, SWG, IG/concrete, sand filter, the pool is 20+ years old probably

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    Re: Algae - sand filter too old?

    Well, if you are following all of the procedures we suggest, yours is the first pool in thousands of thousands that continues to grow algae.

    Please don't think I say that to make you mad or be a smart*** but to point out a basic premise of the TFPC method. Algae will simply not grow in a properly chlorinated pool.

    The sand filter will have little or nothing to do with it. Somewhere, somehow, you are missing something important or you would not have algae.

    PS - a mistook you for a beginner because someone who has been here a while and has a kit usually starts his post with test results.....that's the starting off point.
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

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    Re: Algae - sand filter too old?

    Quote Originally Posted by duraleigh
    Well, if you are following all of the procedures we suggest, yours is the first pool in thousands of thousands that continues to grow algae.
    Please don't think I say that to make you mad or be a smart*** but to point out a basic premise of the TFPC method. Algae will simply not grow in a properly chlorinated pool.
    The sand filter will have little or nothing to do with it. Somewhere, somehow, you are missing something important or you would not have algae.
    PS - a mistook you for a beginner because someone who has been here a while and has a kit usually starts his post with test results.....that's the starting off point.
    I know I make a mistake somewhere. That's why I asked some questions
    I grew up in a country with no private pools. This is all fairly new to me. On top of that I have a house with a very old pool so I struggle.
    I didn't post test results because my question was about the filter. I added the other information to provide some context.

    thank you!
    16000 gallons, SWG, IG/concrete, sand filter, the pool is 20+ years old probably

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    Algae - sand filter too old?

    Would you be able to give a little more detail of how your going about " shocking " we now call it the SLAM process your pool water. SLAM stands for shock level and maintain The SLAM process has to be followed to the T or the result will not be algae free water.
    You already have the proper test kit, I'm just curious about how you are doing the process of getting rid of the algae.
    As for your filter a sand filter is just fine. It will even filter better when slightly dirty. You asked about the clean pressure being ok. Every sand filter is different so there is no clean pressure standard. We recommended backwashing the filter when the pressure raises 20-25% above the clean pressure. If there was algae in your filter the high chlorine level from the SLAM process would kill it off.
    One test result you did not post was CC. Could you post that result ?
    You describe your water as being cloudy. Do you have visible algae in the pool ? Do you have a light in the pool ? Algae likes to hide in the light niche.
    Jeff
    24'x54" AG Morada RTR (by wilbar) 13'500 gal. Hayward Powerflo Matrix 1hp 2 speed. Hayward Perflex EC65 DE filter.

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    Re: Algae - sand filter too old?

    Quote Originally Posted by pwrstrk
    Would you be able to give a little more detail of how your going about " shocking " we now call it the SLAM process your pool water. SLAM stands for shock level and maintain The SLAM process has to be followed to the T or the result will not be algae free water.
    You already have the proper test kit, I'm just curious about how you are doing the process of getting rid of the algae.
    As for your filter a sand filter is just fine. It will even filter better when slightly dirty. You asked about the clean pressure being ok. Every sand filter is different so there is no clean pressure standard. We recommended backwashing the filter when the pressure raises 20-25% above the clean pressure. If there was algae in your filter the high chlorine level from the SLAM process would kill it off.
    One test result you did not post was CC. Could you post that result ?
    You describe your water as being cloudy. Do you have visible algae in the pool ? Do you have a light in the pool ? Algae likes to hide in the light niche.
    I followed the process:
    checked the FC level in the morning and added enough cal-hypo to raise it to at least 16 (a value calculated using poolcalculator) over 1kg if I remember correctly. my CYA is somewhere in the 30-40 range. hard to tell exactly with the tube test in that range.
    an hour later I checked FC again and added more cal-hypo (500grams or so). Repeated it a few times untill the drop in FC wasn't that big. Since then I started to check less frequently.
    I also brushed the walls and the bottom twice during that day. In the evening I added more to raise it above 16 for the night. I kept the cover off all the time and the pump running (with disconnected SWG). Next day I checked FC three times and added cal-hypo accordingly. All together I used like 3+ kg of it. Today (Monday) I checked FC in the morning. water was looking better. I added more chlorine and brushed. Cal-hypo made the water more cloudy but now I know I use the wrong chlorine for the process. That's what they sell us here for the shock/slam process. Now I'm at work so I will check it again in the evening.
    The reading on my filter this morning was still at 12 psi. I didn't backwash during the process at all.

    This time I only tested for CC at the very beginning of the SLAM and it was showing <0.5. Last time I checked for CC every time and I usually check for it twice a month at least and it is always <0.5.
    I'm almost out of R-871 (impossible to buy here) so I need to restrict my tests. At this stage I test in 1ppm increments (5ml of water only).

    I do not have any visible algae and the water is milky white not green any more. I do have a light and I will check what is lurking behind it tonight. I thought algae needed sunlight to survive? I will check anyway.

    CYA 30-40
    FC 16+
    CC 0
    PH 7.5
    CH 200 (haven't tested for a while)
    TA 110 it is higher than recommended for SWG but I have no practical way to lower it.

    cheers
    Pawel
    16000 gallons, SWG, IG/concrete, sand filter, the pool is 20+ years old probably

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    pwrstrk's Avatar
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    Algae - sand filter too old?

    Could you do an OCLT. That would be the last test to pass. From the last results you posted everything looks ok.
    The water clarity problem is from the cal-hypo. If you pass the OCLT, stop using the cal-hypo
    You need to get your CYA level up if your running a SWG. it should be in the 70-80 ppm range.
    Your filter pressure won't raise if there's not a lot of stuff to filter out.
    Jeff
    24'x54" AG Morada RTR (by wilbar) 13'500 gal. Hayward Powerflo Matrix 1hp 2 speed. Hayward Perflex EC65 DE filter.

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    Re: Algae - sand filter too old?

    Quote Originally Posted by pwrstrk
    Could you do an OCLT. That would be the last test to pass. From the last results you posted everything looks ok.
    The water clarity problem is from the cal-hypo. If you pass the OCLT, stop using the cal-hypo
    You need to get your CYA level up if your running a SWG. it should be in the 70-80 ppm range.
    Your filter pressure won't raise if there's not a lot of stuff to filter out.
    got Sodium Hypochlorite today and will continue to SLAM with that.
    I was going to raise CYA to 70-80 but after I get rid of algae. Battling it with such high CYA will get expensive.

    How do you test FC during SLAM with such high CYA? 2oz bottle of 871 will go in a few days...

    thanks.
    Pawel
    16000 gallons, SWG, IG/concrete, sand filter, the pool is 20+ years old probably

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    Re: Algae - sand filter too old?

    2 oz of R-0871 contains roughly 1400-1500 drops. If you consume 40 drops during each test, that's enough for 36 or so tests.
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
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    Re: Algae - sand filter too old?

    If your CH is indeed 200 (this is an easy test to mess up), you probably should keep using the Cal Hypo, as your CH is too low for a concrete/gunite/plaster pool. Have you read through the extended test instructions? Are you using a Speed Stir?

    I agree an OCLT is your first step.
    Built in 1957 44,000 gallon in-ground, Wet Edge Primera Stone in Sky Blue, Intelliflo VF Pump, 600 lb. Pentair Triton II TR-100 Sand Filter, CircuPool RG 60 Plus SWG, TF-100 test kit
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    Re: Algae - sand filter too old?

    you probably should keep using the Cal Hypo,
    I don't think so. OP's pool turns milky when he uses it.....indicating saturation and precipitation. Regardless of test results, I would not use Cal hypo if you are trying to get a pool clear.
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

  18. Back To Top    #18

    Re: Algae - sand filter too old?

    I ditched cal-hypo already. I thought the water was getting milky because of dead algae. I can increase CH with dedicated calcium increaser (this will probably make water milky again) once I'm done with algae. Considering I added like 8kg of cal hypo in last month my CH is probably much higher now.
    Today I can see the bottom of my pool again (just)! My daughter is getting restless without the pool
    Thank you!


    16000 gallons, SWG, IG/concrete, sand filter, the pool is 20+ years old probably

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    Re: Algae - sand filter too old?

    I would do what you are, focus on the FC/SLAM Levels with bleach until all the Algae is completely killed off. If you added 48% Ca Hypo recently that would only be about a 45 PPM increase in CH. Just curious, did you keep the pool going with regular FC levels during the winter months?
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    Re: Algae - sand filter too old?

    Quote Originally Posted by Brushpup
    I would do what you are, focus on the FC/SLAM Levels with bleach until all the Algae is completely killed off. If you added 48% Ca Hypo recently that would only be about a 45 PPM increase in CH. Just curious, did you keep the pool going with regular FC levels during the winter months?
    yep. the pool was covered with FC above 5 all the time, the pump was running for 4h a day (+SWG).
    the water was nice and clear when I uncovered it but there was dead and live algae at the bottom which made the water cloudy once stirred. I did occasionally brush the walls but never the bottom.

    yesterday morning OCLT showed only 1ppm but I continued SLAM just to be sure and this morning it showed 5ppm... I guess I will keep going with SLAM for a bit longer.
    last night I lowered PH from 7.8 to 7.5 (FC in the evening was 7) and the pool was used during the day. could this contribute to failed OCLT test the following night?
    16000 gallons, SWG, IG/concrete, sand filter, the pool is 20+ years old probably

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