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Thread: How can I tell if I have algae?

  1. #1
    Join Date
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    Default How can I tell if I have algae?

    I got my pool last year and, aside from having very hard well water, I didn't have any problems. I put polyquat in the water before closing the pool last fall. I covered the pool, and when we took the cover off this spring lots of water and debris slipped off of the cover and into the water. We tried to syphon most of the water off of the top of the cover, but it was unavoidable. So I ended up with a lot of dirt and leaves at the bottom of the pool. Also, the water was already over 60 degrees when I uncovered the pool. Therefore, algae may have already started growing before I could get the pool completely filled, chemicals in, and the pump going. It was finally warm enough to get in the pool this weekend. I removed the leaves and debris and vacuumed the pool Saturday. I waited for the dirt to settle and vacuumed again on Sunday, and again on Monday. Still, the water is cloudy and a fine dirt settles on the bottom. I have had the pump going 24/7 and have backwashed it numerous times due to the amount of gunk coming out. I've had to continue to add more well water because I'm backwashing so much. I got the TFTest Kits TF-100 yesterday and did a few of the tests. The FC=3, CC=0, TC=3 and CYA was over 100. I read about mixing equal parts of pool water and tap water to test for higher CYA levels, and I will try that tonight to get an accurate reading. I tested the water last night after dark and again early this morning and the numbers were the same, so I'm not losing a lot of chlorine, but is that because the CYA is so high? How can I know if I'm dealing with dirt or with algae? What else can I do to get the water clear? Am I just being too impatient?
    18'x54" round Doughboy pool; 1/2 HP compact pool pump; 12" sand filter; very hard well water; TFTest Kits TF-100

  2. #2
    swimdaddy is offline *Removed User* Weir Watcher swimdaddy 0
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    Default Re: How can I tell if I have algae?

    A few things:

    1. You ALWAYS have algae, to some degree, you are just trying to control it. An algae bloom happens when there is not enough FC to kill it.

    2. You can know if you are fighting an algae bloom with the overnight test. From sundown to just before sun-up, you shouldn't lose more than 1ppm FC. If you do, you are probably fighting something. CC is also an indicator, if its more than 0.5 to 1ppm, you are probably fighting something. According to what you wrote, those look good.

    3. Your CYA is way too high for your FC level, so very soon you will have an algae bloom. According to the "best guess" chart, you should be keeping your FC at 8-15ppm! That's pretty high, and in your part of the country, you probably don't need to have it so high. 50ppm CYA is a good place to be, keeping your FC at 3-6 PPM. In order to drop you CYA, you will have to drain and re-fill, if that's what you want to do.

    4. Your filter will never be able to filter our fine particles, its just too small and sand isn't great at catching small stuff. You would be better off not backwashing it so much. Unless you are fighting algae, don't backwash until your filter unless your filter pressure has risen to the point that return flow is impeded. Your filter will actually work better with some dirt and fine particles trapped in it. You could also add a little DE to the filter to help it trap the small stuff.

    I don't know what the TFTest kit is, maybe someone else does for my information.

  3. #3
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    Default Re: How can I tell if I have algae?

    Thanks for the quick response! I have a couple more questions.

    (1) I don't want to drain the pool and refill because our well water is AWFUL, and last time I filled a pool (smaller Intex pool that I had) with it I spent weeks trying to filter out white powdery stuff--possibly calcium? Anyway, it was quite a process. So with this pool, I had water delivered from town by the volunteer fire department. I'd hate to have to ask them to do that again, LOL! So if I don't drain and refill, and if my CYA stays high, can I continue to maintain the pool by using bleach and keeping the FC at 8-15? With the high CYA level the FC should drop slowly, so I wouldn't have to be adding the bleach as frequently, correct?

    (2) I've been having to backwash so much while I'm vacuuming because the filter pressure rises so much that the vacuum loses suction and the return flow is impeded. The rest of the time the pump seems to be working okay and there's no need to backwash. I ordered some of those "socks" that go in the skimmer to catch smaller particles. Will that help get rid of the finer dirt so that the water is clearer?

    (3) If I add DE, how much do I add? What are the pros and cons of adding DE?
    18'x54" round Doughboy pool; 1/2 HP compact pool pump; 12" sand filter; very hard well water; TFTest Kits TF-100

  4. #4
    Anonymous [GDPR] European in the UK Guest

    Default Re: How can I tell if I have algae?

    1. If you maintain the free chlorine at a high level it will oxidise the CYA slowly away. Using shock levels it would drop quicker but there is also a bacteria solution that will reduce the CYA level. I reduced the CYA from 200ppm down to 50ppm using high doses of chlorine which also helped burn out the quats and get back into control of the pool, the chlorine was cheaper than the empty/refill process.
    2. The filter you have is tiny so it fills with debris quickly hence lots of backwashing. Those socks that go in the skimmer capture the larger particle the sand filter captures the small particles but as I just said yours is too small for the size of the pool, 20" or 24" would be better for that size of pump.
    3 you would only need a tiny amount of DE for a filter that size, almost not worth doing, alternatives such as jolly jelly clarifyer work well but won't work that well in a small filter as they catch the dirt it's delicate jell gets pushed apart by the force of the water trying to blast through it. Gently is much better to catch things in the filter.

  5. #5
    Pappy is offline PF Supporter Widget Weaver Pappy 0
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    Default Re: How can I tell if I have algae?

    I have an Intex 14" sand filter (with a 3/4 hp pump I think). About 1/8 cup of DE is what it likes. That doesn't show much pressure rise, but if I put more than that in, I have to backwash within an hour, EVEN when the pool is SPARKLING clear. DE REALLY improves the water quality in my system.
    Intex 15ftx4ft 4500 gal. 3/4 HP Pentair WhisperFlo pump. Hayward 21" sand filter. Taylor K-2006 & K-1106 kits. PF=27

  6. #6
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    Default Re: How can I tell if I have algae?

    Last evening the pool looked better, but not great. I vacuumed for the 4th day in a row and took a brush and scrubbed the walls down. I think I will bring the chlorine up to shock level for a few days just in case I do have algae. Last night my numbers were: FC=2, CC=.5, CYA=140, PH was at least 8.2--that's as high as my test goes. I added muriatic acid to try to bring the PH down. I added a gallon of bleach (8.25%) to start to bring the chlorine up. That's all the bleach I had on hand. This morning my numbers were: FC=19, CC=.5, and PH was still at least 8.2. I'll purchase more bleach and muriatic acid today. I think I'll try adding the DE as well, if I can find it. I live in a rural area with no pool stores. I'd like to have this pool looking good by June 18th for a BBQ at our house. How long should I keep the pool at shock level to ensure any algae is dead?
    18'x54" round Doughboy pool; 1/2 HP compact pool pump; 12" sand filter; very hard well water; TFTest Kits TF-100

  7. #7
    swimdaddy is offline *Removed User* Weir Watcher swimdaddy 0
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    Default Re: How can I tell if I have algae?

    I would like to here more from Teapot about bringing CYA down with high chlorine? That sounds interesting, never heard that before. Would be interesting to compare the cost of chlorine to the cost of a refill.

    You could keep your CYA at 140, and your FC at 8-15 (probably on the higher side of that), but your shock level is more like 25ppm. Can I ask why your CYA is so high? What do you use in your pool. You shouldn't be using anything with CYA in it at this point.

    I use DE in my filter, works pretty good, and I also occasionally use polyquat algaecide as a clarifier (maybe 2 times a year). BUT, the reason I have to do these things is my filter is too small. Way too small of a surface area and way to big of a pump. Everything gets pushed through and beaten into smaller particles (my theory), so you end up with a cloudy pool.

    I had to order DE off Amazon, Clorox brand, came in a huge box and was pretty cheap.

    I have never used the skimmer socks so I don't no how they work, I know some people on this forum like them.

  8. #8
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    Default Re: How can I tell if I have algae?

    Well, I think I made a rookie mistake (probably a number of them, LOL) and that's how the CYA got so high. I use Kem-Tek 007 Pool and Spa All-in-One Concentrated Chlorinating Granules (or at least I did until I found that the CYA had gotten so high). Now I'm only using bleach 8.25%. When I uncovered the pool and the dirt and debris slipped off of the tarp and into the pool, and I found that the water temp was already well over 60 degrees, I panicked and put the chlorinating granules in without testing the water first. The pool was over halfway full when I closed it last fall. Then I had to slowly fill it with well water because it's too hard on the well to run it and run it until the pool's full. So this process takes several days. In the meantime, the pump was not running because the pool wasn't full enough. So the chlorinating granules were not getting mixed up. They were concentrated in one spot. This is why I'm fearful that algae was starting to grow in other places in the pool. When I finally got the pool full and the pump going I tested PH and chlorine but NOT CYA. This was a mistake because I thought my chlorine levels were fine but they really needed to be much higher. I probably put too much of the granules in when I should've been using straight bleach. So... my cloudy water could be due to one of three things, or a combo of all of them: (1) possible algae; (2) the dirt and debris that got into the pool; or (3) the crappy, hard well water that I used to fill the pool the rest of the way.
    18'x54" round Doughboy pool; 1/2 HP compact pool pump; 12" sand filter; very hard well water; TFTest Kits TF-100

  9. #9
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    Default Re: How can I tell if I have algae?

    Our Home Depot carries DE. The brand is Pooltime.
    26K gal 20x40 rectangular IG vinyl pool; Apr 2014: New pump, liner, auto-cover, & water; Pentair Whisperflo 1HP pump; Pentair Trition sand filter; Cover/Star CS-500 auto cover; Taylor K-2006C; OTO

  10. #10
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    Default Re: How can I tell if I have algae?

    I'm going to try the DE. I can't find it in the stores in my area (small towns). I could drive to Lincoln to get it but that's an hour and a half away, LOL! So I ordered it on Amazon. I'll start by adding about 1/8 of a cup of DE mixed in with pool water and watch the psi on the pump/filter. In the meantime, I keep vacuuming every evening but the water is still cloudy. It's a slow process. I'm still trying to get the chlorine up to shock level. I'm adding bleach and muriatic acid every night just before dark. The numbers this morning were: FC=22, CC=.5, CYA=120, PH=7.8. I hope I'm on the right track!
    18'x54" round Doughboy pool; 1/2 HP compact pool pump; 12" sand filter; very hard well water; TFTest Kits TF-100

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