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Thread: That Last 10%

  1. #1

    That Last 10%

    I just can't seem to get my pool 100% cleared this year Almost there, but still hazy. Here are my stats as of this morning:

    FC: 5
    Combined: 0
    CYA: ~25-30 (estimate after adding 4lbs to prior reading of 15)
    pH: 7.6
    Alk: 70
    Calcium Hardness: 30

    I have a 20x40 vinyl pool that gets sun ~5 hours per day. Ran the FC loss test last night and there was no loss. There are no visible particles floating in the pool and I can see the main drain. It just looks like dull hazy water and it's been that way for 3-4 weeks.

    I know the Calcium Hardness is very low, but does that matter in a vinyl pool?

    Thanks for your thoughts.
    28k gallon in-ground vinyl. Sand filter. Hayward pump. Manual chlorination.

  2. #2
    Administrator JasonLion's Avatar
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    Re: That Last 10%

    It isn't directly related, but get your CYA level up to 40 to 50. That will make this whole process simpler.

    What kind of filter do you have? And how often are backwashing/cleaning it? Backwashing a sand filter too often can reduce it's ability to clear up the water.

    Calcium is just fine at 30 given you have a vinyl liner.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
    TFP Admin. Creator of PoolMath and Pool Calculator. Other handy links: Support this site, TF Test Kits, Pool School

  3. #3

    Re: That Last 10%

    Thanks for your quick reply.

    I have a sand filter and have backwashed only about once a week, so not too often. The pool was a swamp when I first opened it, but I loaded it up with bleach to shock level, brushed, and then vacuumed to waste so I wouldn't kill the filter.

    The sand has not been changed in years. I bought new sand for replacement last year, but when I opened up the filter, the existing sand appeared to be in good shape, so I returned the new sand. I believe the pool was pretty clear last year.

    I will work to get the CYA up. I've had to put a large bottle of bleach in each night which is getting expensive.
    28k gallon in-ground vinyl. Sand filter. Hayward pump. Manual chlorination.

  4. #4

    Re: That Last 10%

    Jason,

    Your question about the filter got me thinking again. I do believe it needs some help. When I inspected the sand last year, it was largely free of debris and it wasn't clumpy. I realize now that the sand hasn't been replaced in at least 12 years. Should I give it an overflow cleaning and see how that works? Any success with that?

    Thanks for your time and thoughts.
    28k gallon in-ground vinyl. Sand filter. Hayward pump. Manual chlorination.

  5. #5
    Mod Squad jblizzle's Avatar
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    Re: That Last 10%

    I think your idea of a good overflow cleaning and sand inspection is a good idea. The odds are that you should not ever need to replace the sand.

    BTW, we recommend backwashing when the pressure goes up 20-25% of the clean pressure ... that could be weekly or much longer than that.

    Also, using a little DE in the filter could help get the last bit clear.
    Jason, TFP Moderator
    18k IG pebblesheen pool, Hayward ProLogic P4 w/ T-15 SWG, Pentair 1HP 2-speed Superflo, Hayward 6020 DE filter
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  6. #6
    Administrator JasonLion's Avatar
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    Re: That Last 10%

    There is no need to replace the sand. I suggest trying adding a little DE to the filter to help it catch the smaller particles more efficiently.

    Backwashing weekly might be too often. How does the filter pressure behave?
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
    TFP Admin. Creator of PoolMath and Pool Calculator. Other handy links: Support this site, TF Test Kits, Pool School

  7. #7

    Re: That Last 10%

    Thanks to both of you.

    If I do try to clean the sand, would I remove the multivalve from the top, drop in the hose, and run it around until the water that flows from the top clears? Should I cover the center pipe to prevent junk from getting into the laterals?

    I found the directions for adding DE in the Pool School so will follow that. My pressure gauge is broken, so sounds like I need to replace that before adding DE.

    Any ideas on where to buy DE? My closest pool store wants $23 for a 20 lb. bag!

    Thanks.
    28k gallon in-ground vinyl. Sand filter. Hayward pump. Manual chlorination.

  8. #8
    Mod Squad jblizzle's Avatar
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    Re: That Last 10%

    Here are some descriptions of the sand cleaning: my-sand-is-channeled-how-to-fix-it-t7626.html

    Definitely need to replace the gauge.

    Lowes/HD usually have DE as well ... can not recall the price.
    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, Dolphin Diagnostic Robotic Cleaner, TF-100 test kit w/ SpeedStir
    Gone: Hayward RS1500 pump, undersized DIY solar heater, Dolphin Dynamic Robotic Cleaner
    Pool School + Test Kit + PoolMath = A TROUBLE FREE POOL

  9. #9

    Re: That Last 10%

    Well that was interesting. Dropped the garden hose in the filter and ran my hand through the sand, and the water turned completely brown. Couldn't run the hose for too long because of the filter location, so I turned the water off, got a siphon going, continued to stir the sand, and drained the murky water out of the filter and into the yard.

    Should I see if this clears up the pool, or will the DE make an even bigger difference? Happy to make the investment, but also happy to keep $25 in my pocket.

    Thanks again for your guidance.
    28k gallon in-ground vinyl. Sand filter. Hayward pump. Manual chlorination.

  10. #10
    Mod Squad jblizzle's Avatar
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    Re: That Last 10%

    With a sand filter, there is a chance that getting it "too clean" will result in worse filtration. Doing what you did is probably a good idea once a year anyway to just make sure things are not clumped up. If your sand was channeled, then useing the hose may have certainly helped.

    The DE just grabs smaller particles in the water that may be causing the cloudy water. That box of DE would likely last you many years as you will not use very much each time.
    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, Dolphin Diagnostic Robotic Cleaner, TF-100 test kit w/ SpeedStir
    Gone: Hayward RS1500 pump, undersized DIY solar heater, Dolphin Dynamic Robotic Cleaner
    Pool School + Test Kit + PoolMath = A TROUBLE FREE POOL

  11. #11

    Re: That Last 10%

    Thanks very much Jason. I'll buy the DE and pick up a new gauge and get to work.
    28k gallon in-ground vinyl. Sand filter. Hayward pump. Manual chlorination.

  12. #12

    Re: That Last 10%

    One other quick question... Will the sand cleaning and the DE powder go to work quickly? The reason I ask is because I also need to raise my CYA, but if I add cyanuric acid, I can't backwash for 48 hours. But if the filter is cleaning more effectively, I'll need to backwash.

    Thanks.
    28k gallon in-ground vinyl. Sand filter. Hayward pump. Manual chlorination.

  13. #13
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    Re: That Last 10%

    Put the CYA in a sock and suspend it in front of a return or put it in the skimmer.
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  14. #14
    Mod Squad jblizzle's Avatar
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    Re: That Last 10%

    Maybe don't add the DE for a few days ... or ...

    If you put the CYA in a sock in front of a return, you can backwash and not likely loose much CYA in the process. The not filter cleaning thing is more for if you dump the CYA into the skimmer for the filter to catch ... or leave the sock in the skimmer.
    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, Dolphin Diagnostic Robotic Cleaner, TF-100 test kit w/ SpeedStir
    Gone: Hayward RS1500 pump, undersized DIY solar heater, Dolphin Dynamic Robotic Cleaner
    Pool School + Test Kit + PoolMath = A TROUBLE FREE POOL

  15. #15

    Re: That Last 10%

    Wanted to follow up on my post. I put CYA in a sock in front of the return and added DE to the skimmer. The pool slowly started to clear. Thanks very much for putting me on the right track.

    Before the pool completely cleared, I left for a trip. Before leaving, I raised FC to 18 and put a floater in the pool. When I returned four days later, FC was 1.5, the pool was cloudy, and a yellow/green algae covered the bottom. I shocked and brushed that night (Tuesday), again last night, and this evening added a quart of polyquat as a backup because I'm not always able to keep up with adding chlorine. Current reading is:

    FC: 9
    CYA: ~40
    pH: 8.0+

    Am concerned about the pH. I know pH rises after shocking, but FC is down to 9 and pH is 8.0+. Should I adjust the pH, or go ahead and shock again this evening. Pool is a hazy light green and I've only been able to filter for a day.

    Thanks for your continued guidance!
    28k gallon in-ground vinyl. Sand filter. Hayward pump. Manual chlorination.

  16. #16
    Mod Squad jblizzle's Avatar
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    Re: That Last 10%

    While FC is < 10, I would adjust the pH down to 7.4 or so and then resume the shock process ... sorry you made such headway and then lost ground ... trips certainly add a wrinkle.
    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, Dolphin Diagnostic Robotic Cleaner, TF-100 test kit w/ SpeedStir
    Gone: Hayward RS1500 pump, undersized DIY solar heater, Dolphin Dynamic Robotic Cleaner
    Pool School + Test Kit + PoolMath = A TROUBLE FREE POOL

  17. #17

    Re: That Last 10%

    Thank you Jason.

    Leaving the pool unattended for a few days causes me headaches every summer -- away for 4 days, then shocking and brushing for 5 days. Am really hoping that adding polyquat to my strategy will help.

    Our pool is surrounded by woods on two sides, so a lot of junk drops in it all day long.

    Will try to get the pH down this evening and reassess tomorrow.
    28k gallon in-ground vinyl. Sand filter. Hayward pump. Manual chlorination.

  18. #18

    Re: That Last 10%

    Results this morning:

    FC: 7.0 (down from 9.0 last night)
    CC: 0.5
    pH: down to 7.3 from 8+ after adding dry acid
    Me: sweaty and want to jump in

    Pool still blue/green hazy. Never can tell whether green is due to remaining algae or reflection off surrounding tall trees.

    Would the decrease in FC be due to addition of quart of polyquat last night, or just algae? Should I shock again tonight, after the sun goes down?

    Thanks.
    28k gallon in-ground vinyl. Sand filter. Hayward pump. Manual chlorination.

  19. #19
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    Re: That Last 10%

    Chlorine does react with Polyquat and the drop would be most noticeable if both doses were high, but in your case you may have other things in the pool so it's probably a combination of both.
    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"

  20. #20

    Re: That Last 10%

    Thank you. So another round of shock and brushing is in order tonight?
    28k gallon in-ground vinyl. Sand filter. Hayward pump. Manual chlorination.

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