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Thread: Filter sending dirty water back into pool

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    Filter sending dirty water back into pool

    Hey all --

    So I had been fighting a hazy/cloudy pool for a couple weeks. Nothing major, just not pretty. Seemed like the more I ran the filter, the cloudier it got, despite having solid chem levels.

    So I took a break from running the (sand) filter more than the usual timer (about 2 hrs a day --- manually turning on for another 2 hrs on average when we're actually in the pool). The pool looked pretty clear.

    Then my wife turned on the filter one morning, and saw the jets shoot out very dark/dirty water back into the (fairly) clear pool. Now it's very cloudy and slightly green. I'm scared to add more chemicals, if the filter is on the fritz and I'll just be wasting time/money.

    Are there any easy ways to see if the filter is working, even with the pool being cloudy/green now? I did open up the filter and tried to break up the sand... but I have no idea if it did anything to fix the problem.

    The sand in the filter is at least 4 summers old. That's when we started renting this house.

    Thanks in advance...
    25x12, inground (pebble tech)
    1hp pump, Pentair Triton sand filter

  2. Back To Top    #2

    Re: Filter sending dirty water back into pool

    You need to Slam the pool.
    pool-school/shocking_your_pool

    When clearing a pool, you need to run the filter continuously until the Slam is complete. Even when the pool is clean and clear, you need more than two hours a day of pump run time.
    pool-school/pump_run_time

    How often do you backwash the filter?

    What does the backwash water look like?

  3. Back To Top    #3

    Re: Filter sending dirty water back into pool

    Quote Originally Posted by JamesW
    You need to Slam the pool.
    pool-school/shocking_your_pool

    When clearing a pool, you need to run the filter continuously until the Slam is complete. Even when the pool is clean and clear, you need more than two hours a day of pump run time.
    pool-school/pump_run_time

    How often do you backwash the filter?

    What does the backwash water look like?
    Like I said in the OP --- I'm worried about the filter itself, not a 'how to' on pool shocking. I appreciate the effort, but it seems as though you didn't read much of the actual OP.

    I backwash the filter when the psi's hit the low-mid 20's... it's usually dark brown and turns clear as it backwashes.
    25x12, inground (pebble tech)
    1hp pump, Pentair Triton sand filter

  4. Back To Top    #4
    Mod Squad woodyp's Avatar
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    Re: Filter sending dirty water back into pool

    Backwash the filter, run it 24 hours straight and tell us what your water looks like. We like testing results too. Balancing your pool is not a waste of money. It's why you have one!
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  5. Back To Top    #5

    Re: Filter sending dirty water back into pool

    You're probably waiting too long to backwash and you might not have enough flow rate to adequately backwash. The pump basket or impeller might be clogged.

    Which size filter do you have?

  6. Back To Top    #6
    freqz's Avatar
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    Re: Filter sending dirty water back into pool

    Quote Originally Posted by JPBoston
    Hey all --

    So I had been fighting a hazy/cloudy pool for a couple weeks. Nothing major, just not pretty. Seemed like the more I ran the filter, the cloudier it got, despite having solid chem levels.

    So I took a break from running the (sand) filter more than the usual timer (about 2 hrs a day --- manually turning on for another 2 hrs on average when we're actually in the pool). The pool looked pretty clear.

    Then my wife turned on the filter one morning, and saw the jets shoot out very dark/dirty water back into the (fairly) clear pool. Now it's very cloudy and slightly green. I'm scared to add more chemicals, if the filter is on the fritz and I'll just be wasting time/money.

    Are there any easy ways to see if the filter is working, even with the pool being cloudy/green now? I did open up the filter and tried to break up the sand... but I have no idea if it did anything to fix the problem.

    The sand in the filter is at least 4 summers old. That's when we started renting this house.

    Thanks in advance...
    For my education, since I'm a noob, what are solid chem levels?

    Did this start before or after you broke up the filter bed?
    25000 gal in ground plaster. '79 vintage. Cartridge filter.

  7. Back To Top    #7

    Re: Filter sending dirty water back into pool

    Quote Originally Posted by woodyp
    Backwash the filter, run it 24 hours straight and tell us what your water looks like.
    Still cloudy and slightly greenish.

    We like testing results too. Balancing your pool is not a waste of money. It's why you have one!
    I didn't mention numbers because they haven't been a problem. But the pool has been steady between PH of 7.4-7.8 and FC has been kept at 5-12 (usually more like 8-10). And sorry, it IS wasting money to pour chlorine in a pool with a busted filter, without figuring out what the problem with the filter is first, or at least while doing it.

    I was hoping for more help figuring out why a filter would shoot dirty water into a clean pool. I mentioned fighting off the slightly cloudy water, and the fact that the more I ran the filter, the cloudier the water got, because it seems connected to the fact that we now see dirty water shooting into the pool from the returns.

    Connect the dots: The pool got cloudier the more I ran the filter, then I stop running the filter as much, pool clears up... then one day, BOOM, a bunch of dirty brown water gets shot into the clear pool when we start up the pump.

    BTW --- I broke up the sand bed AFTER the problem. I don't usually go poking around inside the filter unless I have to.

    ADDED:

    I guess what I was really hoping for were some ideas. Based on what evidence I could provide, what are the chances it is: just algae build-up in the filter, vs sand in the filter is too old, vs bad gasket/other piece of equipment, vs pressure build up and basically the filter backwashed into the pool.

    Attaching a pic that shows the day when the obvious dirty water got sent into the pool. You can see the vacuum lines and the pool is still fairly clear.
    Attached Images Attached Images
    25x12, inground (pebble tech)
    1hp pump, Pentair Triton sand filter

  8. Back To Top    #8
    Mod Squad Bama Rambler's Avatar
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    Re: Filter sending dirty water back into pool

    Tie a sock over a return and see what it catches.
    Raise the FC to high norm and run an OCLT tonight.
    Backwash the filter until the backwash runs clear then leave the sock on the return and see if it catches anything.
    Dave J. TFP Moderator
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  9. Back To Top    #9
    Jeetyet's Avatar
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    Re: Filter sending dirty water back into pool

    Sand filter way too small for your pool. Pump too large for the filter. Bad spider gasket, or some other multi-port problem. Channeled sand. Not enough sand. Waiting too long between backwashings. Not rinsing long enough after backwashing.

    Thats probably not an exhaustive list and I'm no expert on pumps & filters, but those are the reasons that I can think of right now for why the filter would be shooting dirty water thru the returns.
    "The early bird might get the worm, but its the second mouse that gets the cheese." ~ W. Rian Adams
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    Relative's IG Vinyl | 16x32 | ~18,600 gals | Hayward 3/4hp Pump | Hayward S244T Filter | Pentair Model 300 Chlorinator (not used) | Polaris 180

  10. Back To Top    #10

    Re: Filter sending dirty water back into pool

    Hey guys, so a little update w/ pics inside the sand filter.

    So a few nights ago, I added two cups of DE to the sand filter to see if it would come out the returns. Didn't seem to. I left in the DE over night to aid in filtration, and the next morning, the sand in the filter was covered in a green algae-like slime (see green slime pic). In the picture, it's hard to tell, but the green isn't from green water... it's actually like a slime covering on the sand. And btw, the pool got several 'notches' clearer.

    I backwashed, and then the sand was clear again. Ran the filter overnight, without DE, and the sand didn't get covered in green slime. The pool also didn't look any clearer this time.

    So I added DE again, ran overnight, with the same results.

    I know DE is supposed to aid in filtration, but this seems pretty extreme. Does this info narrow anything down?

    Reminder: Green pic is after a night of filtering with DE added thru skimmer at pool. The clearer pic is after backwashing.

    [attachment=1ky4lg3n]IMG_20130924_094756_099.jpg[/attachmentky4lg3n]

    [attachment=0ky4lg3n]IMG_20130924_093330_878.jpg[/attachmentky4lg3n]
    Attached Images Attached Images
    25x12, inground (pebble tech)
    1hp pump, Pentair Triton sand filter

  11. Back To Top    #11
    Jeetyet's Avatar
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    Re: Filter sending dirty water back into pool

    Sure looks like algae to me! If I understand it correctly, live algae is harder to filter than dead and adding the DE helped to catch some of the live stuff and would work even better if it was dead. Probably the "dirty" water coming from the filter after a restart is dead algae instead of dirt.
    "The early bird might get the worm, but its the second mouse that gets the cheese." ~ W. Rian Adams
    .
    Relative's IG Vinyl | 16x32 | ~18,600 gals | Hayward 3/4hp Pump | Hayward S244T Filter | Pentair Model 300 Chlorinator (not used) | Polaris 180

  12. Back To Top    #12

    Re: Filter sending dirty water back into pool

    Quote Originally Posted by Jeetyet
    Probably the "dirty" water coming from the filter after a restart is dead algae instead of dirt.
    Right... but WHY is the sand filter allowing that stuff to go back into the pool (can't be normal, can it)? This all started very gradually, the pool actually got clear for a day before the filter blew in a ton of dirty water, basically like I backwashed directly into the pool. Then the algae bloom happened immediately after that moment. I doubt the filter really needed to be backwashed so badly that it forced it to blow back into the pool... I had backwashed very recently.

    I did another DE test this morning, ran it from approximately 8:45am till 2pm, the pressure was already about 8 psi higher than normal, so I popped the filter top to take a peek... and it seems the DE is the 'base' of that green slime pictured above, as this time the green was much lighter in color, and I could pretty much tell by the texture that it's a layer of DE, colored green by the algae. The pool is crystal clear now, just by keeping Chlorine at 6-8 and PH at 7.6ish.
    25x12, inground (pebble tech)
    1hp pump, Pentair Triton sand filter

  13. Back To Top    #13
    Mod Squad jblizzle's Avatar
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    Re: Filter sending dirty water back into pool

    You have algae. You need to SLAM the pool. Period.

    This is not a waste of money. It is the chlorine that kills the algae ... and it would do so even if you did not have a filter.

    The pool probably looks clearer when you are not running the pump because it is all settling to the bottom. Then when you are running the pump everything is getting stirred back up.

    You seem to be waiting WAY too long to backwash. You should be doing it when the pressure rises 20-25% over the clean pressure. You just said the pressure was already up 8psi which is likely well over 25%.

    You still see green in the filter ... you need to SLAM ... and pass all 3 criteria to know when to stop.

    The pool can look clear but still have algae growing.

    Post up a full set of test results ... what is your CYA? And why is your FC seemingly all over the place?
    Jason, TFP Moderator
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  14. Back To Top    #14

    Re: Filter sending dirty water back into pool

    Not sure why you're being so standoff-ish.

    Like I've stated before... I understand how to shock the pool. The algae itself is not what I'm worried about. You're so steeped in this 'must tell people to 'slam' pool' thing, that you can't answer a simple question.

    I'm asking if it's normal for a sand filter to send dirty water back into the pool. Period.


    This seems counter-intuitive to me... I always figured dirt filtered thru the filter would stay there.

    I don't know. Maybe a possibility is that the algae bloom started off in the filter, sat/grew overnight, and then got blasted back into the pool on startup the next day. Then again, I didn't think adding DE could make such a huge difference in that it could remove all this algae that the sand filter can't.

    Despite having a pool for 4 full summers now, and fighting off several algae blooms... I've never seen such dirty water flowing INTO the pool from the returns. AND I'D LIKE TO KNOW IF MY FILTER IS FUNCTIONING PROPERLY.

    And THAT is why I'm asking how/why such a thing could happen. I honestly don't know. I DO know, however, how to shock a pool. I'm not worried about how to get rid of the algae, I'm worried if my filter is working correctly. (hoping if I repeat myself several dozen times, it will sink in).

    BTW -- Everything I've read from the last 4 years of owning a pool says backwash when psi is 8-10 over the 'clean' number... which is of course, not even germane to what I said in my previous post, which you obviously skimmed. When I mentioned 8psi over, I was talking about how quickly it rose several hours AFTER ADDING DE. That's not the usual schedule.

    If you're SOO concerned about my backwashing schedule, here it is: if it hits 22-23 psi, I backwash (clean psi is about 17-18). Sooner if I get antsy. I doubt I've gone more than 2 weeks without backwashing during the swimming season.
    25x12, inground (pebble tech)
    1hp pump, Pentair Triton sand filter

  15. Back To Top    #15
    Mod Squad jblizzle's Avatar
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    Re: Filter sending dirty water back into pool

    If you are seeing dirt flow into the pool, then your filter is clearly not OK.

    If the clean pressure is 17-18, then you should backwash by 22psi at the latest. You will not see that 8-10psi recommendation on this forum as it just does not make sense if you think about it. An 8 psi rise over a start of 8psi is a lot different than an 8psi rise over 17psi ... going much beyond 25% and the flow rate suffers dramatically.

    You should not be having to backwash every 2 weeks unless your filter is too small or your pool is very dirty or you have algae growing. Many members backwash 1-2 times a year.

    And as the DE article in Pool School states, you need to watch the pressure as it will go up very fast ... especially when you are seeing green algae.

    So, forget the algae (which should not have developed regardless of the filters functionality if adequate FC was maintained). Seeing plumes of **** entering the pool is not OK. So either your sand is channeled, you have a problem with a lateral or something, or there is a problem with your backwash valve or the pump is way too big for the filter.

    Open up the filter. Clean/inspect the sand. Inspect the backwash valve seals. See if that helps. If not, you may need to remove all the sand and see if the filter is damaged.
    Jason, TFP Moderator
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  16. Back To Top    #16

    Re: Filter sending dirty water back into pool

    Quote Originally Posted by JPBoston
    I added two cups of DE to the sand filter to see if it would come out the returns. Didn't seem to.
    Based on this, I think that the filter might be working properly. DE powder is pretty fine, and would typically go through a sand filter if there were a problem. All filters have a limit to what they can catch. Sand can only get down to about 20 to 50 microns. Anything finer will go right through. Mustard algae typically goes through a sand filter. DE can catch particles down to 2 to 5 microns and will do much better at catching mustard algae. I think that you have several issues that might have caused the problem.

    1) Insufficient chlorine allowing algae to grow. Solution: maintain FC levels as shown in the FC/CYA chart. Also, periodically doing an overnight chlorine loss test to detect excessive chlorine loss due to algae and/or other organics.
    2) Insufficient filter run time.
    3) Not backwashing often enough or soon enough.

    I think that if you address these issues, your problem will go away. Either way, the best way to tell is to follow the recommendations and then if the filter still has issues then you can work from there.

  17. Back To Top    #17

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    Re: Filter sending dirty water back into pool

    It is entirely possible you have a broken lateral or bad seals in the filter too. DE put into the filter might stick to the top and not go back into the pool. When mine was bad (broken lateral) it would shoot sand out the returns when the pump started.

    The recommendation to put a sock over the return and have someone else start the pump is valid. It's best if you do it when the pump hasn't been running. That's how I diagnosed my problem.
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  18. Back To Top    #18

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    Re: Filter sending dirty water back into pool

    JPBoston,

    Read the PM I sent you before you post again.
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
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  19. Back To Top    #19

    Re: Filter sending dirty water back into pool

    Thanks for the tips. Will try the sock idea tomorrow, haven't had time between my work schedule and the wife's. I was wondering how to tie the sock on tight enough, so it wouldn't just blow off, but having me hold it while the wife turns on the pump is a good solution.

    I'm thinking it's not a broken lateral, because filter-sand isn't coming into the pool on a constant basis (or at all)... just the really dirty water, and just that one time. I'm starting to think the water channeled thru the filter, sending the nasty water back into the pool and when I broke up the sand bed, solved that problem... now all that's left is the aftermath of having a filter full of dirty water shot back into my pool.

    A moderator has taken exception to my posts, meaning this will probably be my last message here, so thanks again everyone for the tips both on this topic and the few others I have posted over the years.
    25x12, inground (pebble tech)
    1hp pump, Pentair Triton sand filter

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