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Thread: Greyish Powder at Bottom of Pool

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    Greyish Powder at Bottom of Pool

    Hi all,

    I've been getting some greyish powder/dirt collecting at the bottom of my pool since last summer. Its definitely powder/dirt because as soon as you touch it, it disperses into the water. It also vacuums right out very easily on drain. I thought it was the sand in my filter getting old and letting fine particles through (the previous owner had a new filter installed in 2009 and the sand hadn't been changed since then). So I had the sand changed a few weeks ago, vacuumed the pool and everything seemed fine, I wasn't getting any greyish powder forming at the bottom. However one day last week, I applied some algaecide as regular maintenance (about 1 liter of 15% HTH Algae Stop). Later in the evening I put in my granulated chlorine as usual. The next morning my entire pool was a grey cloud!! I couldn't see more than 2-3 inches into the water. It took a few days for the water to clear out (I applied some HTH shock and ran the filter 24 hrs a day) but the grey powder was back with a vengeance all along the bottom of the pool.

    I called the company that had changed my sand and asked them if it was due to the new sand filter. They came to look at the grey residue and said it looked like a water chemistry problem and probably had nothing to do with the new sand. They didn't think it had anything to do with the Algaecide I applied.

    I know my water hardness (calcium) levels have been quite high since I bought the house. On the last reading it was close to 600ppm. I was usually able to lower it by draining off water and then adding new water but this year it hasn't seemed to help.

    Any chance my high levels of calcium are causing this greyish powder problem? If not, any other ideas?

    Thanks in advance.
    In-Ground Dauphin Pool (circa 1970), 21K gallons, Vinyl liner, 1.5 HP Hayward Pump, Hayward Pro Series S-244T Sand Filter, LIQUID CHLORINE!

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    Texas Splash's Avatar
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    Re: Greyish Powder at Bottom of Pool

    Hello and welcome to TFP. Well, I can say that typically we do not advocate the use of algaecides, not only because we maintain the water chemistry continuously to avoid algae, but also because algaecides can add metals or contaminates to the water. The best thing you can do right now, for us to properly help you, is to provide us with a full set of test results from your Taylor K-2006 test kit. We need to see your FC, CC, CYA, PH, TA and CH. If you do not have a Taylor K-2006, it really should be a priority so we can see what's going on in your water. The link below titled "TF-100" will get your to the web site to order the test kit if you don't already have one. Let us know if you have any other questions. Have a nice day.
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    Re: Greyish Powder at Bottom of Pool

    Thanks for the reply. I live in Canada so it's challenging to get my hands on the kits but I believe I can get the Taylor kit delivered here. Once I get it I'll post the results. I do have the test results from my local pool store that I can post but I realize that is not a complete picture.
    In-Ground Dauphin Pool (circa 1970), 21K gallons, Vinyl liner, 1.5 HP Hayward Pump, Hayward Pro Series S-244T Sand Filter, LIQUID CHLORINE!

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    Re: Greyish Powder at Bottom of Pool

    I was reading somewhere else on here that if the 'dirt' disperses as soon as you get near it, it's actually dead algae...so the stuff you're using may be killing the algae to create all of this, but you'll still need the test results to understand how it got to this point.
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    Re: Greyish Powder at Bottom of Pool

    Interesting, I was wondering the same thing about this powder/dirt collecting along the bottom. But I've never seen anything growing in the pool that looked like algae that could generate all that dirt once killed. Or is it possible to have algae/bacteria in the water that is not visible to the eye but once it is killed creates a ton of powder/dirt along the bottom?
    In-Ground Dauphin Pool (circa 1970), 21K gallons, Vinyl liner, 1.5 HP Hayward Pump, Hayward Pro Series S-244T Sand Filter, LIQUID CHLORINE!

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    Re: Greyish Powder at Bottom of Pool

    Quote Originally Posted by Go_Habs_Go View Post
    Interesting, I was wondering the same thing about this powder/dirt collecting along the bottom. But I've never seen anything growing in the pool that looked like algae that could generate all that dirt once killed. Or is it possible to have algae/bacteria in the water that is not visible to the eye but once it is killed creates a ton of powder/dirt along the bottom?

    I had this recently and yes you might not actually see it until it just shows up on the floor.

    Sounds like you need to brush your pool too, you will likely get massive clouds of white when you brush, again dead algae,

    just keep the pump running and scrub 2 times a day, within a week you should be all cleared up and no more powder showing up on the floor.
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    Re: Greyish Powder at Bottom of Pool

    Yeah I haven't been doing a lot of scrubbing this year so maybe that's the source of my problem. I also think the high calcium in my water may be causing the grey powder somehow? I am posting some recent results from a water test done at my local pool store - I know, I know, these are not very reliable but I live in Canada so its hard to get a good kit up here. The local store has a new automated water analysis system and it measures quite a few parameters including CC (Combined Chlorine) so I'll go ahead and post them anyway in case anyone wants to look them over.

    July 4th 2015:
    FCL: 1.54
    TCL: 1.83
    CCL: 0.29
    ph: 8
    adjusted ph: 8
    ta: 49
    adjusted ta: 49
    stab: 3 (I don't use stabilizer)
    ca: 539
    cu: 0
    fe: 0

    Based on these results they told me to add 7kg of Alca+ (essentially baking soda), then 800g of their PH Minus product, then shock the pool. They also wanted to sell me some product to reduce the calcium but I started with the first 3 items to see where that would get me.

    I went back the next day after applying the products and got these results:

    July 5th 2015:
    FCL: 0.23 (it was towards the end of day so most of my chlorine had been destroyed by sunlight, I always add chlorine after dusk).
    TCL: 0.23
    CCL: 0
    ph: 8.1
    adjusted ph: 8.1
    ta: 118
    adjusted ta: 118
    stab: 3 (I don't use stabilizer)
    ca: 528
    cu: 0
    fe: 0

    So my CC was down to 0 and my Alkalinity was good but my ph was still too high due to all the Alca+ product I added. So I went home and added more PH Minus product and then my usual dose of chlorine. So I think I am ok with my basic Alkalinity, ph and Chlorine but my Calcium level is still a problem and I don't know how to bring it down. I have drained off and added a lot of water this summer (lots of vacuuming on drain in order to get rid of the grey powder) but my Calcium levels are still high.

    Anyone have any suggestions on how I can get my Calcium levels down?!! And could this be causing the grey powder/dirt?

    Thanks
    In-Ground Dauphin Pool (circa 1970), 21K gallons, Vinyl liner, 1.5 HP Hayward Pump, Hayward Pro Series S-244T Sand Filter, LIQUID CHLORINE!

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    Re: Greyish Powder at Bottom of Pool

    Until you can get reliable test results please keep brushing and adding liquid chlorine. Don't add anything else, just chlorine until and possibly CYA but I'd have to see your own test for that. Pool stores are notorious for getting that one wrong and you do NOT want to overshoot on that as the only way to lower too high CYA is to drain and replace water.
    Your vinyl pool doesn't NEED calcium. So if you've been adding it STOP. Have you been using CalHypo to disinfect the pool with?

    Oh yeah one more thing- TFPC doesn't recommend ever needing to change sand out (unless converting from Baqua pool to chlorine pool). Sand is good for billions of years they say and you can service your sand filter by cleaning the sand instead.
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    Re: Greyish Powder at Bottom of Pool

    Quote Originally Posted by YippeeSkippy View Post
    Your vinyl pool doesn't NEED calcium. So if you've been adding it STOP. Have you been using CalHypo to disinfect the pool with?
    Yes, I've been using Calcium Hypochlorite 65% (chlorine granules) for the last 3 years and I believe the previous owner did the same. I also use the same for shocking the pool. I think the calcium levels have been building up over the years to get to the point they are at now.

    Should I consider draining a foot or so of water out of the pool and refilling it with clean city water in order to reduce my calcium levels? I went for another analysis this weekend and my calcium was at 493ppm. I also recently changed a section of hose near my pool pump and there was some white stuff coating the inside of the hose. When it dried it flaked off. Is this calcium deposit??!

    I'm in a bind because I live in Quebec and its not easy to get a good test kit here. I also need to research where to buy liquid chlorine and how much to add in my pool. I have 2 kids under the age of 2 so its really hard to get a minute to do anything lately!!

    Thanks for any help/advice you can provide in the meantime...
    In-Ground Dauphin Pool (circa 1970), 21K gallons, Vinyl liner, 1.5 HP Hayward Pump, Hayward Pro Series S-244T Sand Filter, LIQUID CHLORINE!

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    Re: Greyish Powder at Bottom of Pool

    I had cloudy water again this Sunday so I went for another pool water analysis and here are the results. I know you would prefer for me to have a test kit for more reliable results but like I said it's a bit of a challenge to get one where I live. I had just shocked the pool the previous evening hence the high chlorine numbers:

    July 11th 2015:
    FCL: 8.17
    TCL: 10.19
    CCL: 2.02
    ph: 7.9
    adjusted ph: 7.9
    ta: 100
    adjusted ta: 100
    stab: 1 (I don't use stabilizer)
    ca: 489
    cu: 0
    fe: 0.4

    I lowered my ph based on these numbers but didn't do anything else other than run the filter 24hrs. This morning the water was better but again I have some grey dirt collecting all along the bottom. I'm pretty sure this is my calcium problem but other than stopping to use calcium hypochlorite anything else I can do?!
    In-Ground Dauphin Pool (circa 1970), 21K gallons, Vinyl liner, 1.5 HP Hayward Pump, Hayward Pro Series S-244T Sand Filter, LIQUID CHLORINE!

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    Mod Squad YippeeSkippy's Avatar
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    Re: Greyish Powder at Bottom of Pool

    Do they sell good old fashioned "Laundry Bleach" up there?

    Do you have any friends in the US who could assist you in obtaining a pool test kit?
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    Re: Greyish Powder at Bottom of Pool

    Yes we have regular bleach here. There are also pool stores that sell liquid chlorine but the one near my home doesn't stock it so I need to find one that does. In any case it's probably more expensive than regular bleach so I need to get a large quantity of regular bleach, see what percentage it is and then do the math to figure out how much to put in my pool. I still will need to get rid of CH that I currently have and I still won't have an accurate way to measure my FC without a good kit.

    I do have family in the US but not sure the next time I will see them!!

    In the meantime I am still struggling with my pool. Woe is me
    In-Ground Dauphin Pool (circa 1970), 21K gallons, Vinyl liner, 1.5 HP Hayward Pump, Hayward Pro Series S-244T Sand Filter, LIQUID CHLORINE!

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    Re: Greyish Powder at Bottom of Pool

    Sadly the only way to lower CH is to perform some water exchange

    Your last test results (pool store?) show iron of 0.4....how's your water look? Has that been a problem in the past?
    My Amazon Smile for November12K Fiberglass IG, Infinity 4000 automatic cover, SWCG, Hayward Sand Filter, Hayward 1.5 Pump, Doheny Discovery Robot, Savi Melody LED pool lights, outdoor speakers and other assorted doo-dads. Sundance Altamar Hot Tub.
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    Re: Greyish Powder at Bottom of Pool

    Yeah I will try to dump out and replace water this weekend to get the CH down to more manageable levels. Other than the occasional cloudiness the water looks good so not sure about the iron levels. My last 2 tests at the pool store had the iron at 0.
    In-Ground Dauphin Pool (circa 1970), 21K gallons, Vinyl liner, 1.5 HP Hayward Pump, Hayward Pro Series S-244T Sand Filter, LIQUID CHLORINE!

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    Re: Greyish Powder at Bottom of Pool

    You need to get more chlorine into that pool to SLAM it based on your last reported test amounts (via pool store). Your CC's are entirely too high, indicating algae or something but all you need is the chlorine, not the added calcium that CalHypo has.

    Can you drop your pH to about 7.2 and proceed with a SLAM after you manage to get a test kit (Taylor's K-2006 is apparently avail in CA). The SLAM procedure can be found in Pool School up at the top right of this website.

    - - - Updated - - -
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    Re: Greyish Powder at Bottom of Pool

    Yeah I noticed the CC being over 2 on my last test but I had shocked the pool the night before (with calhypo) and we've had such a cool summer here so far I can't imagine I have algae in the pool. Weird. But I'll try to pick up some bleach this weekend and go with that.
    In-Ground Dauphin Pool (circa 1970), 21K gallons, Vinyl liner, 1.5 HP Hayward Pump, Hayward Pro Series S-244T Sand Filter, LIQUID CHLORINE!

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    Re: Greyish Powder at Bottom of Pool

    Until you lower the CH to the 250-300ppm range you need to keep the pH lower, around 7.0 to 7.2 This will prevent the excess calcium from depositing on pool surfaces and prevent calcium clouding. You can use dry acid or Muriatic Acid to lower the pH. Use PoolMath to determine how much acid you need. You can also use poolmath to determine chlorine requirements as well.

    As for cool water and algae, it will grow quickly until water temps drop to around 60 degrees. You have a nascent algae bloom and have been adding just enough chlorine to keep it from getting out of control. Once you have killed all the algae and balance the water you should see a big difference in the water quality of your pool. You will need to add some stabilizer, about 30ppm to protect the chlorine from premature burn off in the sun.
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    Re: Greyish Powder at Bottom of Pool

    Quote Originally Posted by zea3 View Post
    Until you lower the CH to the 250-300ppm range you need to keep the pH lower, around 7.0 to 7.2 This will prevent the excess calcium from depositing on pool surfaces and prevent calcium clouding. You can use dry acid or Muriatic Acid to lower the pH. Use PoolMath to determine how much acid you need. You can also use poolmath to determine chlorine requirements as well.

    As for cool water and algae, it will grow quickly until water temps drop to around 60 degrees. You have a nascent algae bloom and have been adding just enough chlorine to keep it from getting out of control. Once you have killed all the algae and balance the water you should see a big difference in the water quality of your pool. You will need to add some stabilizer, about 30ppm to protect the chlorine from premature burn off in the sun.
    great post, good information.
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    Re: Greyish Powder at Bottom of Pool

    Quote Originally Posted by zea3 View Post
    Until you lower the CH to the 250-300ppm range you need to keep the pH lower, around 7.0 to 7.2 This will prevent the excess calcium from depositing on pool surfaces and prevent calcium clouding. You can use dry acid or Muriatic Acid to lower the pH. Use PoolMath to determine how much acid you need. You can also use poolmath to determine chlorine requirements as well.
    Ok, I will work on this and let you know how it turns out.

    Quote Originally Posted by zea3 View Post
    As for cool water and algae, it will grow quickly until water temps drop to around 60 degrees. You have a nascent algae bloom and have been adding just enough chlorine to keep it from getting out of control. Once you have killed all the algae and balance the water you should see a big difference in the water quality of your pool. You will need to add some stabilizer, about 30ppm to protect the chlorine from premature burn off in the sun.
    Are you saying I have an algae problem because my combined chlorine level in my last test was over 2? Just trying to follow your reasoning so I understand better.

    So should I shock the pool first (I'll try the SLAM method) or do I try to lower the pH first? Or lower the CH first by emptying out water? Then SLAM? What order should I be doing this in?
    In-Ground Dauphin Pool (circa 1970), 21K gallons, Vinyl liner, 1.5 HP Hayward Pump, Hayward Pro Series S-244T Sand Filter, LIQUID CHLORINE!

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    Mod Squad zea3's Avatar
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    Re: Greyish Powder at Bottom of Pool

    I'm diagnosing by the symptoms you have reported, cloudy water and grayish "dirt" that puffs away when touched, two things that usually indicate an algae bloom has begun. If left unattended for a day or two you would start to see green algae accumulate. Elevated CC indicate something organic in the water, usually algae but not always, however it is always an indication that you need to complete the slam process.

    If you plan to drain and replace water to lower the CH go ahead and do that first, adjust pH to around 7.2, then begin the slam process.
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