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Thread: Grey stains on bottom of pool

  1. Back To Top    #1

    Grey stains on bottom of pool

    Hi guys I have a marcite pool that was painted and it was green.

    I shocked it clean and sparkling but now there are some grey areas on the bottom of the pool. I tested some on the steps by rubbing my hand over it and it was coming off. I assume it's left over algae which will be killed off over time. however the owners don't like it and I would like to get rid of it a.s.a.p.

    I tried brushing which I don't like doing to a painted pool but that didn't help. A steal bristle brush would probably work but then would definitely take paint off.

    any suggestions? maybe chemical?

    thanks.
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  2. Back To Top    #2
    polyvue's Avatar
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    Re: Grey stains on bottom of pool

    Quote Originally Posted by IslandPool
    Hi guys I have a marcite pool that was painted and it was green.

    I shocked it clean and sparkling but now there are some grey areas on the bottom of the pool. I tested some on the steps by rubbing my hand over it and it was coming off. I assume it's left over algae which will be killed off over time. however the owners don't like it and I would like to get rid of it a.s.a.p.

    any suggestions? maybe chemical?
    Must be tough to distinguish algae in a pool that always looks like aglae!

    What do the test results show? pH, FC, CC, TA, CH and CYA

    I too would be hesitant to brush a painted pool. It doesn't sound like you're convinced that the algae has completely retreated. If you post back chemical test results, provide a bit more info on the pool (filter type, pump, gallons, how it's chlorinated etc.)

    Sorry I don't know any magic bullets... probably need a more certain diagnosis before recommending treatment.
    14,555 gal in-ground 16'x29' white plaster Pool w/spa (2007); Goldline Aqua Logic AQL-PS-8 control w/Aqua Cell 15 Salt Water Chlorination (SWCG); Hayward TriStar 1HP (1.85 SF) main / 1.5HP (1.60 SF) spa pumps; Hayward Swimclear cart filter C4025, ColorLogic LED lights; Tankless SP-18-4 electric heater; Polaris 280 cleaner.
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    View of spiral galaxy in Ursa Major NGC6217 - Hubble Telescope 2009

  3. Back To Top    #3

    Re: Grey stains on bottom of pool

    Quote Originally Posted by polyvue
    Quote Originally Posted by IslandPool
    Hi guys I have a marcite pool that was painted and it was green.

    I shocked it clean and sparkling but now there are some grey areas on the bottom of the pool. I tested some on the steps by rubbing my hand over it and it was coming off. I assume it's left over algae which will be killed off over time. however the owners don't like it and I would like to get rid of it a.s.a.p.

    any suggestions? maybe chemical?
    Must be tough to distinguish algae in a pool that always looks like aglae!

    What do the test results show? pH, FC, CC, TA, CH and CYA

    I too would be hesitant to brush a painted pool. It doesn't sound like you're convinced that the algae has completely retreated. If you post back chemical test results, provide a bit more info on the pool (filter type, pump, gallons, how it's chlorinated etc.)

    Sorry I don't know any magic bullets... probably need a more certain diagnosis before recommending treatment.
    the pool is pristine clear and blue and sparkling. just the grey areas on the bottom.

    ok the pool is 12,000 gallons.

    FC is very high like 10ppm
    pH is 7.4
    I can't get a TA reading but the test kit I have says not to test if FC is high. so probablt can't read TA as FC is too high. but pool looks really great.

    The test kit I have is Guardex and only tests FC, pH and TA

    I want to get a Taylor kit but I can't find one on the island.

    The filter is a Hayward EC65

    Don't know what type pump. just a single phase pump.

    Its chlorinated using 7 day chlorine tablets. I shock it with Cal Hypo. It is a marcite pool that is painted blue.
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  4. Back To Top    #4
    polyvue's Avatar
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    Re: Grey stains on bottom of pool

    Quote Originally Posted by IslandPool
    the pool is pristine clear and blue and sparkling. grey areas on the bottom.

    12,000 gallons.

    FC is very high like 10ppm
    pH is 7.4
    I can't get a TA reading but the test kit I have says not to test if FC is high. so probablt can't read TA as FC is too high. but pool looks really great.

    The test kit I have is Guardex and only tests FC, pH and TA

    I want to get a Taylor kit but I can't find one on the island.

    Several FAS-DPD test kits recommended, I think you can get both by mail order: pool-school/pool_test_kit_comparison

    The filter is a Hayward EC65

    OK -- a DE filter. Has it been backwashed lately?

    Hayward Perflex Extended-Cycle D.E. filter EC65A

    Performance Data
    Effective Filtration 34 ft. area
    Design Flow Rate 68 GPM
    Turnover (In Gallons) 32,640 8 Hours
    Turnover (In Gallons) 40,800 10 Hours


    Don't know what type pump. just a single phase pump.

    Its chlorinated using 7 day chlorine tablets. I shock it with Cal Hypo. It is a marcite pool that is painted blue.


    What are the chlorine tabs? If they are Dichlor or Trichlor, a lot of CYA has been added over time... which could explain recurring algae if there isn't much available chlorine. Have to have a CYA test result to confirm this. When you upgrade your test kit to something better, you'll want to test for both Free Chlorine (FC) and Combined Chlorine (CC). The CC might also tell us something.

    If you've had to shock regularly or often with Cal-Hypo, that may have led to too much calcium. Same answer... gotta test for CH

    My guess is that one or both of the chemicals you can't test now are quite high:
    Calcium Hardness (CH) and Cyanuric Acid (CYA)

    Now, this information does nothing for the grey stuff at the bottom of the pool but better testing and water balance control may pay off in the longer term. The DE filter (if clogged) and unidentified pump (if undersized) could be contributing to circulation and/or balance issues.

    Other members here may be able to contribute add'l advice, so check back in and get yourself a really good test kit! good luck


    14,555 gal in-ground 16'x29' white plaster Pool w/spa (2007); Goldline Aqua Logic AQL-PS-8 control w/Aqua Cell 15 Salt Water Chlorination (SWCG); Hayward TriStar 1HP (1.85 SF) main / 1.5HP (1.60 SF) spa pumps; Hayward Swimclear cart filter C4025, ColorLogic LED lights; Tankless SP-18-4 electric heater; Polaris 280 cleaner.
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    View of spiral galaxy in Ursa Major NGC6217 - Hubble Telescope 2009

  5. Back To Top    #5

    Re: Grey stains on bottom of pool

    Quote Originally Posted by polyvue
    Quote Originally Posted by IslandPool
    the pool is pristine clear and blue and sparkling. grey areas on the bottom.

    12,000 gallons.

    FC is very high like 10ppm
    pH is 7.4
    I can't get a TA reading but the test kit I have says not to test if FC is high. so probablt can't read TA as FC is too high. but pool looks really great.

    The test kit I have is Guardex and only tests FC, pH and TA

    I want to get a Taylor kit but I can't find one on the island.

    Several FAS-DPD test kits recommended, I think you can get both by mail order: pool-school/pool_test_kit_comparison

    The filter is a Hayward EC65

    OK -- a DE filter. Has it been backwashed lately?

    Hayward Perflex Extended-Cycle D.E. filter EC65A

    Performance Data
    Effective Filtration 34 ft. area
    Design Flow Rate 68 GPM
    Turnover (In Gallons) 32,640 8 Hours
    Turnover (In Gallons) 40,800 10 Hours


    Don't know what type pump. just a single phase pump.

    Its chlorinated using 7 day chlorine tablets. I shock it with Cal Hypo. It is a marcite pool that is painted blue.


    What are the chlorine tabs? If they are Dichlor or Trichlor, a lot of CYA has been added over time... which could explain recurring algae if there isn't much available chlorine. Have to have a CYA test result to confirm this. When you upgrade your test kit to something better, you'll want to test for both Free Chlorine (FC) and Combined Chlorine (CC). The CC might also tell us something.

    If you've had to shock regularly or often with Cal-Hypo, that may have led to too much calcium. Same answer... gotta test for CH

    My guess is that one or both of the chemicals you can't test now are quite high:
    Calcium Hardness (CH) and Cyanuric Acid (CYA)

    Now, this information does nothing for the grey stuff at the bottom of the pool but better testing and water balance control may pay off in the longer term. The DE filter (if clogged) and unidentified pump (if undersized) could be contributing to circulation and/or balance issues.

    Other members here may be able to contribute add'l advice, so check back in and get yourself a really good test kit! good luck


    last week I took the filter apart and cleaned the flex tubes with mutiatic acid. so filter is clean and jets working really well. good pressure.

    after I vacuum this week I backwashed and recharged filter.

    chlorine is high still. I use those 3" slow tablets. one lasts a week in this pool.

    pH is perfect.

    yes I need a better test kit. could order it online and have it shipped through a freight forwarder. kinda hard getting things shipped over here. there is one or two companies that sell the Taylor but were out of them.
    status: gone fishing :p

  6. Back To Top    #6
    Ohm_Boy's Avatar
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    Re: Grey stains on bottom of pool

    Your chlorine may be high, or it may not be. FC=10 may seem like a high number, but unless you know the CYA (stabilizer) levels, you cannot know whether or not it is an effective level. The necessary FC level depends upon how much CYA is in the water, and 10 may be shock level if CYA=20, but it's barely minumum at CYA=100. See the chart here.

    If your chlorine tabs are Trichlor, they are adding CYA as they dissolve, and CYA accumulates over time. Unlike chlorine, it never gets used up or goes away unless you drain water and replace with fresh.

    So you really need to know the CYA level before you assume that your FC is high.

    Still no help with the grey stains though. Sorry.
    [center:1kpalu48]Helpful Links: Pool School | CYA/Chlorine Chart | Pool Calculator[/center:1kpalu48]

  7. Back To Top    #7

    Re: Grey stains on bottom of pool

    Quote Originally Posted by Ohm_Boy
    Your chlorine may be high, or it may not be. FC=10 may seem like a high number, but unless you know the CYA (stabilizer) levels, you cannot know whether or not it is an effective level. The necessary FC level depends upon how much CYA is in the water, and 10 may be shock level if CYA=20, but it's barely minumum at CYA=100. See the chart here.

    If your chlorine tabs are Trichlor, they are adding CYA as they dissolve, and CYA accumulates over time. Unlike chlorine, it never gets used up or goes away unless you drain water and replace with fresh.

    So you really need to know the CYA level before you assume that your FC is high.

    Still no help with the grey stains though. Sorry.
    Thanks for the info. I guess I need a better test kit. how do I test for CYA? also my chlorine level on the test kit only goes up to 3. so I'm guessing 10 but its pretty dark reading...could be higher.

    this is the test kit i have....


    these are the tablets I'm using...


    yes it has cyanuric acid in the tablets.

    I also put 3 scoops of this to clear the pool up..


    it has no cyanuric acid in it but adds calcium hardness.
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    polyvue's Avatar
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    Re: Grey stains on bottom of pool

    Quote Originally Posted by IslandPool
    I guess I need a better test kit. how do I test for CYA? also my chlorine level on the test kit only goes up to 3. so I'm guessing 10 but its pretty dark reading...could be higher.
    Yes, I think you know that a low-end residential test kit is going to be of limited use to you in managing this pool. Even the standard residential kits provide the ability to test for Free Chlorine (FC) and Combine Chlorine (CC) up to 5 ppm. The standard turbidity test for CYA will be an essential component in a kit used to test an outdoor pool chlorinated with Dichlor/Trichlor tabs or powder. As Ohm_Boy suggested, knowing (or guessing at) the level of Total Chlorine can't tell you how much free chlorine is actually available to do the necessary work of santizing and oxidizing.

    CYA tests can be purchased stand-alone

    http://www.taylortechnologies.com/produ ... KitID=2462
    http://www.tftestkits.net/index.php?act ... oductId=24

    or as part of a complete test kit

    http://www.taylortechnologies.com/produ ... KitID=2230
    http://www.tftestkits.net/index.php?act ... roductId=2
    14,555 gal in-ground 16'x29' white plaster Pool w/spa (2007); Goldline Aqua Logic AQL-PS-8 control w/Aqua Cell 15 Salt Water Chlorination (SWCG); Hayward TriStar 1HP (1.85 SF) main / 1.5HP (1.60 SF) spa pumps; Hayward Swimclear cart filter C4025, ColorLogic LED lights; Tankless SP-18-4 electric heater; Polaris 280 cleaner.
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    View of spiral galaxy in Ursa Major NGC6217 - Hubble Telescope 2009

  9. Back To Top    #9

    Re: Grey stains on bottom of pool

    Quote Originally Posted by polyvue
    Quote Originally Posted by IslandPool
    I guess I need a better test kit. how do I test for CYA? also my chlorine level on the test kit only goes up to 3. so I'm guessing 10 but its pretty dark reading...could be higher.
    Yes, I think you know that a low-end residential test kit is going to be of limited use to you in managing this pool. Even the standard residential kits provide the ability to test for Free Chlorine (FC) and Combine Chlorine (CC) up to 5 ppm. The standard turbidity test for CYA will be an essential component in a kit used to test an outdoor pool chlorinated with Dichlor/Trichlor tabs or powder. As Ohm_Boy suggested, knowing (or guessing at) the level of Total Chlorine can't tell you how much free chlorine is actually available to do the necessary work of santizing and oxidizing.

    CYA tests can be purchased stand-alone

    http://www.taylortechnologies.com/produ ... KitID=2462
    http://www.tftestkits.net/index.php?act ... oductId=24

    or as part of a complete test kit

    http://www.taylortechnologies.com/produ ... KitID=2230
    http://www.tftestkits.net/index.php?act ... roductId=2
    Thanks. I will check and see if i can get one here. might be able.
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  10. Back To Top    #10
    polyvue's Avatar
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    Re: Grey stains on bottom of pool

    Quote Originally Posted by IslandPool
    my parents are going state side in a week or so and will ask them to pick up a Taylor test kit for me. I love the islands but there is a down side to livin on an island.
    Taylor manufactures hundreds of test kits but many stores will only stock what sells quickly, often cheap $20 kits. If possible, ask your parents to bring down a kit that includes both a FAS-DPD chlorine test and CYA test. That should guide the selection to Taylor K-2006. If you're going to be servicing multiple pools, you'll want to procure its older brother (sister?) containing 2 oz. agents: K-2006C. Prices are $75 and $135, slightly lower at some pool supply websites.

    Taylor K-2006 Complete (FAS-DPD Chlorine)

    Taylor K-2006C Service Complete (FAS-DPD Chlorine)
    14,555 gal in-ground 16'x29' white plaster Pool w/spa (2007); Goldline Aqua Logic AQL-PS-8 control w/Aqua Cell 15 Salt Water Chlorination (SWCG); Hayward TriStar 1HP (1.85 SF) main / 1.5HP (1.60 SF) spa pumps; Hayward Swimclear cart filter C4025, ColorLogic LED lights; Tankless SP-18-4 electric heater; Polaris 280 cleaner.
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    View of spiral galaxy in Ursa Major NGC6217 - Hubble Telescope 2009

  11. Back To Top    #11

    Re: Grey stains on bottom of pool

    Quote Originally Posted by polyvue
    Quote Originally Posted by IslandPool
    my parents are going state side in a week or so and will ask them to pick up a Taylor test kit for me. I love the islands but there is a down side to livin on an island.
    Taylor manufactures hundreds of test kits but many stores will only stock what sells quickly, often cheap $20 kits. If possible, ask your parents to bring down a kit that includes both a FAS-DPD chlorine test and CYA test. That should guide the selection to Taylor K-2006. If you're going to be servicing multiple pools, you'll want to procure its older brother (sister?) containing 2 oz. agents: K-2006C. Prices are $75 and $135, slightly lower at some pool supply websites.

    Taylor K-2006 Complete (FAS-DPD Chlorine)

    Taylor K-2006C Service Complete (FAS-DPD Chlorine)
    Thanks. looks like going to have to get a Taylor from the states. so the Taylor K-2006C would be the one to go with? Yes I plan on servicing more pools.
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  12. Back To Top    #12
    frustratedpoolmom's Avatar
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    Re: Grey stains on bottom of pool

    TFtestkits ships everywhere in the world except Canada - that might be a better price than the Taylor kit. It uses the same reagents but you get larger bottles on some of the tests. You could order all your supplies and extra of some, the first time to save on shipping costs.
    Helpful links: Pool School; CYA/Chlorine Chart
    24' round AG pool, 52" high, Raypak heater; Waterway 2 spd Pump;
    150 Sq ft. Clearwater Cartridge Filter; Former and DISSATISFIED "Pool Frog" owner
    http://www.PerfectlyClearPoolService.com

  13. Back To Top    #13

    Re: Grey stains on bottom of pool

    Quote Originally Posted by frustratedpoolmom
    TFtestkits ships everywhere in the world except Canada - that might be a better price than the Taylor kit. It uses the same reagents but you get larger bottles on some of the tests. You could order all your supplies and extra of some, the first time to save on shipping costs.
    Thanks. something to consider.
    status: gone fishing :p

  14. Back To Top    #14

    2nd time shocking pool. I think the grey stains were algae

    Posts Merged by Moderator for Consistency

    as soon as I shocked the pool again the grey "stains" turned black. I got scared and though I had burnt the paint on the pool but I think that's the algae being killed. here are some photos of the black stuff. please tell me I haven't burnt the paint and it is indeed algae...
    Attached Images Attached Images
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  15. Back To Top    #15
    polyvue's Avatar
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    Re: 2nd time shocking pool. I think the grey stains were algae

    Quote Originally Posted by IslandPool
    as soon as I shocked the pool again the grey "stains" turned black. I got scared and though I had burnt the paint on the pool but I think that's the algae being killed. here are some photos of the black stuff. please tell me I haven't burnt the paint and it is indeed algae...
    Hi IslandPool,

    I don't think it's very likely that you "burnt the paint" by shocking. It looks like aglae... dead or dying, probably. You'll be familiar with these questions: what did you use to shock the pool? how much? and what is the volume of the pool water? Is it safe to assume that the main pump was on during the administration of whatever you used to shock? And, finally (you know this is coming! --) can you post the test results? Whatever you have at this point is good. Well, not good, but better than guessing!
    14,555 gal in-ground 16'x29' white plaster Pool w/spa (2007); Goldline Aqua Logic AQL-PS-8 control w/Aqua Cell 15 Salt Water Chlorination (SWCG); Hayward TriStar 1HP (1.85 SF) main / 1.5HP (1.60 SF) spa pumps; Hayward Swimclear cart filter C4025, ColorLogic LED lights; Tankless SP-18-4 electric heater; Polaris 280 cleaner.
    __
    View of spiral galaxy in Ursa Major NGC6217 - Hubble Telescope 2009

  16. Back To Top    #16

    Re: 2nd time shocking pool. I think the grey stains were algae

    Quote Originally Posted by polyvue
    Quote Originally Posted by IslandPool
    as soon as I shocked the pool again the grey "stains" turned black. I got scared and though I had burnt the paint on the pool but I think that's the algae being killed. here are some photos of the black stuff. please tell me I haven't burnt the paint and it is indeed algae...
    Hi IslandPool,

    I don't think it's very likely that you "burnt the paint" by shocking. It looks like aglae... dead or dying, probably. You'll be familiar with these questions: what did you use to shock the pool? how much? and what is the volume of the pool water? Is it safe to assume that the main pump was on during the administration of whatever you used to shock? And, finally (you know this is coming! --) can you post the test results? Whatever you have at this point is good. Well, not good, but better than guessing!
    Thanks for the reply its very much appreciated.

    ok the pool is one of my new clients. I met it with FC = 0 and a very low pH

    the pool is 10,000 to 12,000 gallons. the filter is a Hayward D.E. EC65. haven't checked the pump yet. got to remember to tomorrow.

    Fist thing I did was added 10 small scoops of stabilized Desert Granules which ended up turning a clear pool green.

    so a few days later I shocked the pool with 3 scoops of Cal Hypo sprinkled around the pool with the pump on and then brushed. This cleared the pool up nice and blue and the pH went to 7.4 were it has stayed since.

    I too think the grey stuff was dieing algae and shocking it today was a good idea. I sprinkled 2 scoops of Cal Hypo with the pump off then quickly brushed and put the pump back on when the grey turned black. I then mixed 1 scoop with water and spread it around the pool. so 3 scoops of Cal Hypo today to shock it again. I now remember mixing Cal Hypo in a bucket of water and pouring it around the edge of the pools when I used to do the chemicals for a pool company 20 years ago.

    I think the FC is off the chart for real now.
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  17. Back To Top    #17
    frustratedpoolmom's Avatar
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    Re: Grey stains on bottom of pool

    The kind of blind dosing of the pool chemistry that you are doing could cause you problems down the road. I highly recommend you order one of the recommended kits asap.

    I have read posts of metal staining when a pool is shocked, it's not uncommon for copper stains to deposit and turn black if the FC and PH rise suddenly. I'd be concerned that this isn't just an algae issue.

    You may want to invest in a stain i.d. kit.

    One way to tell if the black stains are algae is to rub a chlorine tablet on the stain. if it vanishes its organic/algae, if not, it could be metal.
    Helpful links: Pool School; CYA/Chlorine Chart
    24' round AG pool, 52" high, Raypak heater; Waterway 2 spd Pump;
    150 Sq ft. Clearwater Cartridge Filter; Former and DISSATISFIED "Pool Frog" owner
    http://www.PerfectlyClearPoolService.com

  18. Back To Top    #18

    Re: Grey stains on bottom of pool

    Quote Originally Posted by frustratedpoolmom
    The kind of blind dosing of the pool chemistry that you are doing could cause you problems down the road. I highly recommend you order one of the recommended kits asap.

    I have read posts of metal staining when a pool is shocked, it's not uncommon for copper stains to deposit and turn black if the FC and PH rise suddenly. I'd be concerned that this isn't just an algae issue.

    You may want to invest in a stain i.d. kit.

    One way to tell if the black stains are algae is to rub a chlorine tablet on the stain. if it vanishes its organic/algae, if not, it could be metal.
    Thanks.

    I did test a small area and it seems to be coming off with the granules but your suggestion of using a tablet is much better. I will try that tomorrow..actually from now on. thanks! I do need a better test kit. I will see if I can buy some extra tests from the pool supply store. especially the stain i.d. kit if they have it. or any extra tests would be good.
    status: gone fishing :p

  19. Back To Top    #19
    polyvue's Avatar
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    Re: Grey stains on bottom of pool

    Quote Originally Posted by IslandPool
    I too think the grey stuff was dieing algae and shocking it today was a good idea. I sprinkled 2 scoops of Cal Hypo with the pump off then quickly brushed and put the pump back on when the grey turned black. I then mixed 1 scoop with water and spread it around the pool. so 3 scoops of Cal Hypo today to shock it again. I now remember mixing Cal Hypo in a bucket of water and pouring it around the edge of the pools when I used to do the chemicals for a pool company 20 years ago.

    I think the FC is off the chart for real now.
    Perhaps they did things differently 20 years ago... but in the modern post-industrial age of communcation (translation: today) it's best to be more precise in your measurements. I have no idea what a scoop is, but even if I knew the exact shape, size and color that wouldn't help me to understand; the person doing the scooping determines how much it takes to fill the scoop. Much better to record additions of dry chemicals by weight and concentration: "Added 10 ounces of 48% Cal Hypo." Ditto with analysis of pool water. It's challenging enough to obtain precision and accuracy when using carefully designed tests to determine the parts per million (ppm) of a particular constituent in a sample solution. If your customer tells you that he thinks chlorine is "off the chart", you'll want to know, "how far?" and maybe "which chart?" The ability to accurately diagnose and treat problem pools begins with proper testing.

    Everyone around here has had to re-learn stuff they thought they already knew. I had an above-ground spa for many years, dutifully spooning in Dichlor granules whenever the water felt "icky" and when that failed, as it often did, I dumped the water. The chlorine level, according to my little test kit, would go up, up, up, and then --poof!!-- vanish completely. I thought that was a good thing! To my knowledge, no horrible diseases were communicated between guests sitting in that spa, but no one was paying me to manage it either!

    Go find that chart, then beg, borrow or steal a good test kit. You're really going to need it.
    14,555 gal in-ground 16'x29' white plaster Pool w/spa (2007); Goldline Aqua Logic AQL-PS-8 control w/Aqua Cell 15 Salt Water Chlorination (SWCG); Hayward TriStar 1HP (1.85 SF) main / 1.5HP (1.60 SF) spa pumps; Hayward Swimclear cart filter C4025, ColorLogic LED lights; Tankless SP-18-4 electric heater; Polaris 280 cleaner.
    __
    View of spiral galaxy in Ursa Major NGC6217 - Hubble Telescope 2009

  20. Back To Top    #20

    Re: Grey stains on bottom of pool

    Quote Originally Posted by polyvue
    Quote Originally Posted by IslandPool
    I too think the grey stuff was dieing algae and shocking it today was a good idea. I sprinkled 2 scoops of Cal Hypo with the pump off then quickly brushed and put the pump back on when the grey turned black. I then mixed 1 scoop with water and spread it around the pool. so 3 scoops of Cal Hypo today to shock it again. I now remember mixing Cal Hypo in a bucket of water and pouring it around the edge of the pools when I used to do the chemicals for a pool company 20 years ago.

    I think the FC is off the chart for real now.
    Perhaps they did things differently 20 years ago... but in the modern post-industrial age of communcation (translation: today) it's best to be more precise in your measurements. I have no idea what a scoop is, but even if I knew the exact shape, size and color that wouldn't help me to understand; the person doing the scooping determines how much it takes to fill the scoop. Much better to record additions of dry chemicals by weight and concentration: "Added 10 ounces of 48% Cal Hypo." Ditto with analysis of pool water. It's challenging enough to obtain precision and accuracy when using carefully designed tests to determine the parts per million (ppm) of a particular constituent in a sample solution. If your customer tells you that he thinks chlorine is "off the chart", you'll want to know, "how far?" and maybe "which chart?" The ability to accurately diagnose and treat problem pools begins with proper testing.

    Everyone around here has had to re-learn stuff they thought they already knew. I had an above-ground spa for many years, dutifully spooning in Dichlor granules whenever the water felt "icky" and when that failed, as it often did, I dumped the water. The chlorine level, according to my little test kit, would go up, up, up, and then --poof!!-- vanish completely. I thought that was a good thing! To my knowledge, no horrible diseases were communicated between guests sitting in that spa, but no one was paying me to manage it either!

    Go find that chart, then beg, borrow or steal a good test kit. You're really going to need it.
    will do. thanks.

    so you guys use a scale to weigh chemicals?
    status: gone fishing :p

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