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Thread: I was told black algae, but...

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    I was told black algae, but...

    I'm pretty certain it isn't.

    20160424_103506[2].jpg

    Some history on our pool - the pool was completed in the summer of 2003. The pool is gunite and white plaster. It is roughly about 28,000 gallons. Pool equipment is a Pentair WhisperFlo 2HP pump & Pentair DE 4048 Filter. The deep end is about 8 1/2 feet deep. For the first few years we had a neighbor that services pools and we had him taking care of it. The first few years the pool looked great, but then we started to notice yellow algae. I discussed this with him and he didn't feel it was a big deal. He dumped a few more gallons of chlorine and put a few tablets in. I had to brush it in between the weekly services, and the algae came off easily when brushed. My wife, who wasn’t working at the time, said his services consisted of 5 minutes and what she saw was him for the most part dropping tablets in a floater. She said she never saw him testing the water.

    I made a decision that I would take care of the pool. I brought a water sample down to the local pool supply store and they recommended using Yellow Treat and to bump up the chlorine. This seemed to work for a period of time, but the yellow algae never really went away. About year 6 the pool place had a ah-ha moment when they tested for phosphates. The level was above 2,000 which they said was the reason we are having the yellow algae problem, we’re feeding the algae. OK, that makes sense. We were in need of repainting the rocks and redoing the slide so we waited on what they were proposing. We drained the pool, had the rocks and the slide painted, and then refilled the pool. This was done in the winter.

    Towards the end of the summer, year 7 the yellow algae started to come back. The water was tested and the phosphates were above the 2,000 level. They recommended a phosphate removal product. I followed the instructions and took the filers out and cleaned them. New DE was added and then the product was dumped into the pool. Within a Ĺ hour the filter was getting plugged up and there was sediment in the bottom of the pool. I had to backwash the filter 2 times before it maintained normal pressures.

    We thought this took care of it until a water sample was brought in about a month later. The phosphate level was still above 2,000. They were scratching their heads trying to figure out what’s going on. I’m given another bottle of the phosphate remover and I purchase a special cleaner for the filter grids, more chlorine, and another 25 pound bag of DE. I repeat the cleaning of the filter, but this time I soak the filter grids in this special cleaner. I put the filter back together and add DE and then the phosphate remover. Same as before, there’s sediment in the bottom of the pool and the filter plugs up quickly. Backwashed a few more times and then the pressure is normal. We leave the pump running for 24 hours again.

    The yellow algae returns. I’m kind of tired of this and it’s gotten pretty expensive between the chemicals and electricity. I call a friend of mine who cleans pools. He’s not close, or I would have had him doing this. I explain what’s been going on. He’s never used this stuff, but he’s heard from others that PoolRX works on problem algae. I take a trip to the local pool store and they’ve got this stuff in stock. I follow the instructions and lower the amount of chlorine. Amazingly the yellow algae is gone and I think we go the whole summer without it coming back.

    I didn’t attribute the side effects to the PoolRX at that time, but as I’m thinking about this, that quite possibly was what happened. Hang on to this thought for a little bit longer. In the winter I started to notice some stains on the white plaster. The staining was bluish green. Then I started to notice some black dots. This went on for a few years until the black dots were like a spider web effect. I included a picture. For the most part the black stuff was only in the deep end of the pool, with a little bit in the spa and some on the swim step. Brushing it, it doesn’t come off. I drained the spa and acid washed it. The black stuff came off and it hasn’t returned.

    A few weeks ago I went to the pool store and they said the black stuff is probably black algae and recommended using Algatec. We dumped that in and have been brushing the pool with a metal brisle brush. It’s not coming off. I think what we have is staining from using the PoolRX. Sooo…

    I have a few questions – (A few of you might be thinking, Thank God, I wondered when he’d get to this point. )
    I know I need a good testing kit. Do I need to test for copper, phosphates, or anything else in addition to kit?
    The filter has a slight leak at the bottom. 3 years ago I had replaced the top for a leak. 6 of my filter grids have slight tears in the filter. Do I stick with a DE filter, or go to a cartridge?
    About 6, or 7 years ago the pump went out and I replaced it with the same unit. How much of a cost benefit would I get with a variable speed pump? Our area is all electric and the prices have been rising.
    The staining – is there a method for determining what it is? If it is metal staining is there a method to get rid of that short of draining and acid washing the pool? We’re in year 5 of a drought and the promised El Nino hasn’t materialized. The local water company frowns on draining pools and water is costly as it's in short supply.

    Thanks for hanging in this long!

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    Mod Squad jblizzle's Avatar
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    Re: I was told black algae, but...

    Welcome to TFP!!!

    That is not black algae (can you scrap it off with a fingernail and smear it on paper and see green?)
    That looks like calcium scaling combined with metal stains.

    Now I will read your novel

    -Pump is bigger than you need.
    -Filter is too small.
    -Phosphates are meaningless is you maintain the appropriate chlorine level ... forget what the pool store is telling you. Yes, phosphates are food for algae, but if the chlorine is killing the algae, why does it matter how much food there is?
    -Phosphate removers can make a mess of your filter, just another reason not to worry about them.
    -Uh Oh, PoolRx adds metals. TFP NEVER!!! recommends adding metals to your pool

    Ah, finally the questions
    - Let the pool store test for metals. Forget about phosphates. Invest in one of the Recommended Test Kits
    - Like I said above, your filter is too small. These are the minimum sizes I would recommend: 400 sqft cartridge, 31" diameter sand, or 72 sqft DE. Type is personal preference: Pool School - Pool Filter Comparison
    - That pump is WAY bigger than you need if you do not have a spa or big water features. One option would be to put a 2 speed motor on your existing pump and run on low, but still bigger than you need. Likely your power is expensive enough that a VS would be worth it. Although you might only need one of the smaller ones like the SuperFlo VS.
    - I am guessing that your CH is very high and that allowed calcium scaling to start and the metal stains are occurring there as well. The metal staining might be removed by doing an Ascorbic Acid treatment as discussed in a link in Dealing with Metals in your Water. But, the calcium scaling, would require an acid wash or a long term chemistry regiment and a LOT of brushing.
    Jason, TFP Moderator
    18k IG pebblesheen pool, Hayward ProLogic P4 w/ T-15 SWG, Pentair 1HP 2-speed Superflo, Hayward 6020 DE filter
    500 sqft Heliocol solar panels, ThePoolCleaner, TF-100 test kit w/ SpeedStir
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    Re: I was told black algae, but...

    Hi Jason,
    Thanks for taking the time and the great advice!

    That's interesting that the pump is too large and the filter is too small. We had a ton of problems with the pool contractor and eventually we ended up firing him when it was about 75% completed. This was after a year of delays. Unlike some of his other customers we weren't out of too much money and we were able to complete the project. The end result for the pool contractor was a 4 year jail sentence for "Diversion of Construction Funds."

    We actually have 2, 2HP pumps. One for the pool/spa and the other is for the water features. If I'm going to spend money on this pool, which I have to, I might change the pump as well as a new filter. It sounds like there are pros and cons to each type of filter and you don't have a preference either way.

    Thanks again for the reply,
    Pool is gunite and white plaster construction with a spa. It is roughly about 28,000 gallons. Pool equipment is (2) Pentair WhisperFlo 2HP pumps - One is for the pool & spa & the other is used for water features - slide & water fall. Pentair DE 4048 Filter

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    Mod Squad jblizzle's Avatar
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    Re: I was told black algae, but...

    Oh, well now that I know you have a spa and water feature and 2 pumps (SIGNATURE!!!) Your pump may not be over sized since it has to run the spa jets. I would no longer recommend the smaller VS pump. So either a 2-speed motor on your existing main pump, or one of the larger VS pumps.

    I have only ever had DE. If I ever replace my filter, I would strongly consider a giant cartridge filter so that I would not be pumping out my salt. Although there is some advantage to pumping out the water for backwashing in that is lowers the CH. Sand is the easiest to deal with, but slowest to filter. So, yeah, lots of + and -
    Jason, TFP Moderator
    18k IG pebblesheen pool, Hayward ProLogic P4 w/ T-15 SWG, Pentair 1HP 2-speed Superflo, Hayward 6020 DE filter
    500 sqft Heliocol solar panels, ThePoolCleaner, TF-100 test kit w/ SpeedStir
    Pool School + Test Kit + PoolMath = A TROUBLE FREE POOL
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    Re: I was told black algae, but...


    I took a water sample in to get tested while I was out this weekend. I specifically asked to have the water tested for metals. I also asked what they thought was at the bottom of the pool and how to take care of that. We went into a Leslie's store that's about 20 miles from the house. The guy who first helped us evidently was new as he wasn't sure if they tested for that. The guy that was training him said they did. Here's the results -

    FAC - 5 PPM
    TAC - 5 PPM
    CH - 470 PPM
    CYA - 90 PPM
    TA - 90
    pH - 7.8
    Copper - 0
    Iron - 0
    TDS - 3,200
    Phosphates - 2,500

    One of the people in charge was helping a customer and was watching the test results and both of the guys helping me. He runs from the back counter and grabs some products and plops them down on the counter in front of me. One of them is a phosphate remover.

    Um, thanks, I'm concerned about the staining and wanted to know about metals. The new guy prints out the report and dumps the water sample. So, the metals are at 0? You wanted to test for metals? Um ,yeah. My impression was they're concerned about selling products and not addressing what I was there for. I realize in retail quite often what brings someone into the store has nothing to do with what they need. But...

    I have to go home and grab another water sample. I bring it to the local independent pool store to see what they have to say. The person that tests for metals isn't there? They test the water.


    Chlorine (It doesn't say TAC, or FAC) 2.0 PPM
    pH 7.6
    CYA 120
    TA 140
    TDS 415
    Phosphates 2,500+

    Heís mostly concerned with the CYA levels & phosphates and recommends taking the tablets out and removing some water and refilling the pool. He starts on the high phosphates and I mention the roughly $600 experiment with their store. I think he remembers me and drops it.



    I leave and go to Leslieís #2 who is right around the corner from the independent store. 3rd. test result.

    FAC 5 PPM
    TAC 5 PPM
    CH - 370
    CYA - 100
    TA - 100
    pH - 7.6
    Copper - 0
    Iron - 0
    TDS - 2,400
    Phosphates - 1,000

    Not that I was intending to do an experiment on water testing,but I found it interesting the varied results and also that the independent pool store and Leslie's had different levels allowed.

    Leslie's FAC & TAC - 1- 4 PPM Versus 1.5 - 2.0 (TAC & FAC not differentiated)
    Leslie's pH 7.2 - 7.8 versus 7.4 - 7.6
    TA 80 - 120 - both
    Leslie's CYA 30 - 99 versus 60 80
    Leslie's TDS Less than 2,500 versus 0 - 2,000

    Iím wondering about this, the testing and the varied results Ė I would think they all should have good test kits, but the results should be repeatable, right? What happened? If I have my own test kit I should expect repeatable results, right? Are these tests subjective and that would explain the differences? I guess Iím going to be doing some more reading here.



    Thanks again!

    Pool is gunite and white plaster construction with a spa. It is roughly about 28,000 gallons. Pool equipment is (2) Pentair WhisperFlo 2HP pumps - One is for the pool & spa & the other is used for water features - slide & water fall. Pentair DE 4048 Filter

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    Mod Squad jblizzle's Avatar
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    Re: I was told black algae, but...

    And now you see why we do not trust pool testing and urge you to invest in one of the Recommended Test Kits and to trust your own testing which will be more consistent.

    Also, I think the metal tests can be off a good bit. It is also possible for them to read low because the metal is already deposited on the pool surface.
    Jason, TFP Moderator
    18k IG pebblesheen pool, Hayward ProLogic P4 w/ T-15 SWG, Pentair 1HP 2-speed Superflo, Hayward 6020 DE filter
    500 sqft Heliocol solar panels, ThePoolCleaner, TF-100 test kit w/ SpeedStir
    Pool School + Test Kit + PoolMath = A TROUBLE FREE POOL
    If you found TFP helpful and we saved you money ... Become a TFP Supporter!

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