algae that doesn't go away no matter how high the chlorine

Chaya

Well-known member
Jul 28, 2019
50
Lakewood, New Jersey
Hello! I’m no expert and have owned a pool for only a year now. Just tossing out an idea as I can sense it’s been a frustrating experience for you.

Reading through your thread, it seems you’ve maintained some really high chlorine levels for some time. I also notice that your location is listed as New Jersey.

I’ve got a friend in NJ who said that ragweed pollen is really bad there now. It started at the end of August, which roughly tracks with your statement that you’ve been seeing the yellow streaks on your pool floor for about a month.

Given that it doesn’t seem to be responding to chlorine, and apparently isn’t clinging to the walls of the pool, is there a chance this is ragweed pollen in your pool? Do you see it on other surfaces (like your car) or perhaps floating on the pool surface at all?

I don’t have enough experience to tell you how to test that theory, but I’m sure others here do. Just wanted to share that thought since I had just talked to my friend about the pollen problem in your area.
i appreciate the suggestion, but its not sounding right to me. i don't see anything on any other surfaces and i think i do recognize this as algae.
 

aeh0603

Well-known member
Apr 6, 2016
237
San Diego, CA
I'm going to preface this by saying I didn't re-read your entire thread, but I did glance over it again.

If I'm understanding correctly, you have been slamming for algae for about a week and are not understanding why the algae is not completely dead and gone yet. In the past you have used typical pool store methods and they have worked well for you, but this time it didn't work as anticipated so you are now trying a TFP SLAM Process for the first time. You are now very familiar with the SLAM article, but have made a few modifications (targeting FC above SLAM level and using Cal Hypo instead of liquid chlorine).

In my experience reading lots of these threads, there are a few things that can make a SLAM take a longer time.
  1. Starting with a swamp (super green water, can't see the bottom, unknown solids on the bottom, etc.) - this does not seem apply to you.
  2. Not brushing every surface in your pool (walls, floor, steps, etc.) at least once per day
  3. Not testing and adding FC often enough - the minimum is twice a day, but the process will go faster if you test 3-4 times per day. This is hard if you work, but a schedule that seems to work for most is first thing in the morning, as soon as you get home from work, after dinner, and before you go to bed.
  4. The CYA test was performed incorrectly (proper lighting and test method are critical) leading to a false lower CYA reading (and therefore a lower than necessary FC target)
  5. Algae is hiding somewhere and you just haven't found it yet... this can sometimes be a tricky one, and might be the problem you are having.
    • If you have any features like a waterfall, fountains, solar, etc., make sure you are running the SLAM level FC water through them once or twice a day.
    • Check you skimmer and wear door carefully for signs of algae. The wear door has nooks and crannies algae can hide in, including the tube where the foam goes to keep the top of the door floating at the surface.
    • If you have a removable pool light with a niche behind it, make sure to remove the light and make sure there is no algae hiding in the niche behind it.
    • I've seen once or twice that someone with an above ground, or in ground liner pool had algae on the other side of the liner that was somehow getting through... they didn't find it until they replaced their liner (I don't remember what pool surface you have but I think you mentioned vinyl liner)
Some other questions and comments specific to your situation
  • Have you been noticing progress at all during your SLAM? Has there been a reduction in the amount of algae you see or an improvement in water clarity?
  • Targeting slightly above your SLAM level is fine (i.e. 30, when your target is 28), but too much higher is really just a waste of money because the FC will burn off in the sun faster than it kills the algae because your CYA is no longer protecting it. The people targeting FC levels much higher than their SLAM level are usually the people complaining that they are spending excessive amounts of money on chlorine and not clearing the algae any faster. It's ok if your FC level dips a bit below SLAM target while you are at work, just bring it back up as soon as you get home.
  • With the TFP method it's better if you measure your chemical additions, yes this may mean you are only using a partial bag. I use plastic measuring cups for wet and dry chemicals, other people use a kitchen scale for dry and plastic measuring cup for wet, other people approximate based on % of the container (i.e. if pool math says you need 0.5 pounds of Cal Hypo and it comes in 1 pound bags, adding about half the bag is close enough)
  • Not related to your SLAM, but I believe you said you have a vinyl liner pool and do not test CH because it's not relevant to a vinyl pool. While this is partially true I do want to clarify this. For vinyl pools, there is no minimum CH, so areas with low CH in their fill water often don't test CH very often. That said, high CH levels can cause scaling problems in any pool type. Since you are using Cal Hypo as your FC source and Cal Hypo adds Calcium along with the FC, I do recommend that you test CH (Calcium Hardness) periodically to make sure it does not get too high. Testing CH once every couple weeks, or once a month is probably plenty, but you should have a general idea what it is to prevent scaling.
  • I think you also mentioned your CC has been testing at 0.2 or less... This tells me that you are using the 25ml test for FC. You can save money on test chemicals and still retain plenty of accuracy by using a 10ml water sample and a single scoop of powder when testing FC/CC. Doing it this way, each drop is 0.5, so count the drops to clear then divide by 2 to get your FC level. With a target of 28 FC for your slam this will likely improve your testing accuracy since you will be using fewer drops to achieve your result (and therefore reducing testing error)
 
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Chaya

Well-known member
Jul 28, 2019
50
Lakewood, New Jersey
I'm going to preface this by saying I didn't re-read your entire thread, but I did glance over it again.

If I'm understanding correctly, you have been slamming for algae for about a week and are not understanding why the algae is not completely dead and gone yet. In the past you have used typical pool store methods and they have worked well for you, but this time it didn't work as anticipated so you are now trying a TFP SLAM Process for the first time. You are now very familiar with the SLAM article, but have made a few modifications (targeting FC above SLAM level and using Cal Hypo instead of liquid chlorine).

In my experience reading lots of these threads, there are a few things that can make a SLAM take a longer time.
  1. Starting with a swamp (super green water, can't see the bottom, unknown solids on the bottom, etc.) - this does not seem apply to you.
  2. Not brushing every surface in your pool (walls, floor, steps, etc.) at least once per day
  3. Not testing and adding FC often enough - the minimum is twice a day, but the process will go faster if you test 3-4 times per day. This is hard if you work, but a schedule that seems to work for most is first thing in the morning, as soon as you get home from work, after dinner, and before you go to bed.
  4. The CYA test was performed incorrectly (proper lighting and test method are critical) leading to a false lower CYA reading (and therefore a lower than necessary FC target)
  5. Algae is hiding somewhere and you just haven't found it yet... this can sometimes be a tricky one, and might be the problem you are having.
    • If you have any features like a waterfall, fountains, solar, etc., make sure you are running the SLAM level FC water through them once or twice a day.
    • Check you skimmer and wear door carefully for signs of algae. The wear door has nooks and crannies algae can hide in, including the tube where the foam goes to keep the top of the door floating at the surface.
    • If you have a removable pool light with a niche behind it, make sure to remove the light and make sure there is no algae hiding in the niche behind it.
    • I've seen once or twice that someone with an above ground, or in ground liner pool had algae on the other side of the liner that was somehow getting through... they didn't find it until they replaced their liner (I don't remember what pool surface you have but I think you mentioned vinyl liner)
Some other questions and comments specific to your situation
  • Have you been noticing progress at all during your SLAM? Has there been a reduction in the amount of algae you see or an improvement in water clarity?
  • Targeting slightly above your SLAM level is fine (i.e. 30, when your target is 28), but too much higher is really just a waste of money because the FC will burn off in the sun faster than it kills the algae because your CYA is no longer protecting it. The people targeting FC levels much higher than their SLAM level are usually the people complaining that they are spending excessive amounts of money on chlorine and not clearing the algae any faster. It's ok if your FC level dips a bit below SLAM target while you are at work, just bring it back up as soon as you get home.
  • With the TFP method it's better if you measure your chemical additions, yes this may mean you are only using a partial bag. I use plastic measuring cups for wet and dry chemicals, other people use a kitchen scale for dry and plastic measuring cup for wet, other people approximate based on % of the container (i.e. if pool math says you need 0.5 pounds of Cal Hypo and it comes in 1 pound bags, adding about half the bag is close enough)
  • Not related to your SLAM, but I believe you said you have a vinyl liner pool and do not test CH because it's not relevant to a vinyl pool. While this is partially true I do want to clarify this. For vinyl pools, there is no minimum CH, so areas with low CH in their fill water often don't test CH very often. That said, high CH levels can cause scaling problems in any pool type. Since you are using Cal Hypo as your FC source and Cal Hypo adds Calcium along with the FC, I do recommend that you test CH (Calcium Hardness) periodically to make sure it does not get too high. Testing CH once every couple weeks, or once a month is probably plenty, but you should have a general idea what it is to prevent scaling.
  • I think you also mentioned your CC has been testing at 0.2 or less... This tells me that you are using the 25ml test for FC. You can save money on test chemicals and still retain plenty of accuracy by using a 10ml water sample and a single scoop of powder when testing FC/CC. Doing it this way, each drop is 0.5, so count the drops to clear then divide by 2 to get your FC level. With a target of 28 FC for your slam this will likely improve your testing accuracy since you will be using fewer drops to achieve your result (and therefore reducing testing error)
wow! thanks for all the info - which i will have to go through in more detail. but i want to very briefly respond to your ask about progress in water clarity etc.
actually my water is crystal clear and i notice nothing on the bottom visually right now. Only when i brush do i see a little bit cloud up. its that final bit of algae i'm having trouble getting rid of. (Waiting to go home and vacuum once more....)

its just that in past cycles of this nightmare it seemed that the minute i left the pool's side... the tiny bit of algae at the bottom (which was not even visible without brushing), spread and grew till there were visible areas of light yellow on the floor of pool after a couple of days.
 

aeh0603

Well-known member
Apr 6, 2016
237
San Diego, CA
wow! thanks for all the info - which i will have to go through in more detail. but i want to very briefly respond to your ask about progress in water clarity etc.
actually my water is crystal clear and i notice nothing on the bottom visually right now. Only when i brush do i see a little bit cloud up. its that final bit of algae i'm having trouble getting rid of. (Waiting to go home and vacuum once more....)

its just that in past cycles of this nightmare it seemed that the minute i left the pool's side... the tiny bit of algae at the bottom (which was not even visible without brushing), spread and grew till there were visible areas of light yellow on the floor of pool after a couple of days.
Oh good, you are at the last part of the slam then. I would focus on #2 and #5 from my post above, brushing everything and looking for sources of hidden algae... that said if it's only been a week, it may just be a matter of POP (pool owner patience) :). In that case you need to just keep doing what your doing and let the process work. I promise you, if you stick with TFP it will work. Good luck!

Oh and feel free to keep asking questions if you have them :)
 

HSBigDaddy

Member
Aug 25, 2012
6
i see that your mustard algae description IS different than what i have. "as a layer of silt" and "nickel sized spots" sounds different that the layer of yellowish streaking on bottom or slope of pool that i see. i sure so after years of thinking i had mustard algae (because a tech told me so over the phone...) i think i am coming to realize that i really don't have it after all and am instead struggling with plain old algae. I really do hope you are finished you battle!

Please advise - why are you closing tomorrow, wouldn't the temp of the water go down to about 60 in just another 2-3 wks? my pool was 65 degrees today and i thought that was the whole point in waiting for long to close (so that we could open cleaner). Also, i'm wondering why you would want to lower the chlorine content of the water. please advise, because i wanted to make sure there was plenty of chlorine in it when i closed. is that wrong?

Lastly, thank you for the advice on the liquid chlorine. My issue is the extra trip to the store and the weight of the item and the quantity i have been using. Sounds like an awful lot of work. Can you explain why you found it superior? Also, did you find it difficult to have to add the chlorine daily (instead of putting 3" tabs into a chlorinator and then being done for the week)? I really would like to hear because i see that liquid is the recommended chlorine again and again, but i have only used it in limited amounts and never thought it was very practical.
Ok, so the pool is closed as of last Sunday. The reason I wanted it closed now is because the leaves are starting to fall and it becomes unproductive if multiple leaves are at the bottom of the pool using up the chlorine. As I said, I'm not sure now that my problem is MA or pollen so I'm thinking it's pollen. As for lowering the chlorine level, all advice I see says before closing, to properly balance the water. Closing with my level at 25ppm isn't properly balanced. Also, the winter kit I use has a chemical (don't remember which one) that requires the chlorine to be lower than what mine was before adding it. As for the liquid chlorine, the main reason is because using 3 inch tabs in my chlorinator adds Cyanuric Acid to the pool water. I use tabs at the beginning of the season to help get my CYA up to level, then I switch to liquid chlorine. Also, I used to shock with calcium hypochlorite and I found that using the cheaper powder, it would seemingly not fully dissolve and I would get cloudy water or grainy material on the pool bottom. I only use liquid now and my work has been a lot less. I don't have to add it daily, more like twice or three times weekly to keep my level good. I never got a reply about the chlorine lowering chemical though so I closed the pool with a high level. Don't think it will do any harm but who knows what the pools going to look like when I open it.
 

Chaya

Well-known member
Jul 28, 2019
50
Lakewood, New Jersey
Oh good, you are at the last part of the slam then. I would focus on #2 and #5 from my post above, brushing everything and looking for sources of hidden algae... that said if it's only been a week, it may just be a matter of POP (pool owner patience) :). In that case you need to just keep doing what your doing and let the process work. I promise you, if you stick with TFP it will work. Good luck!

Oh and feel free to keep asking questions if you have them :)
The good news is that I vacuumed Friday afternoon and brushed. i didn't notice any yellow clouding up when i brushed, only a bit of brown/grey. So i am cautiously optimistic that i am done...
 

Chaya

Well-known member
Jul 28, 2019
50
Lakewood, New Jersey
I'm going to preface this by saying I didn't re-read your entire thread, but I did glance over it again.

If I'm understanding correctly, you have been slamming for algae for about a week and are not understanding why the algae is not completely dead and gone yet. In the past you have used typical pool store methods and they have worked well for you, but this time it didn't work as anticipated so you are now trying a TFP SLAM Process for the first time. You are now very familiar with the SLAM article, but have made a few modifications (targeting FC above SLAM level and using Cal Hypo instead of liquid chlorine).

In my experience reading lots of these threads, there are a few things that can make a SLAM take a longer time.
  1. Starting with a swamp (super green water, can't see the bottom, unknown solids on the bottom, etc.) - this does not seem apply to you.
  2. Not brushing every surface in your pool (walls, floor, steps, etc.) at least once per day
  3. Not testing and adding FC often enough - the minimum is twice a day, but the process will go faster if you test 3-4 times per day. This is hard if you work, but a schedule that seems to work for most is first thing in the morning, as soon as you get home from work, after dinner, and before you go to bed.
  4. The CYA test was performed incorrectly (proper lighting and test method are critical) leading to a false lower CYA reading (and therefore a lower than necessary FC target)
  5. Algae is hiding somewhere and you just haven't found it yet... this can sometimes be a tricky one, and might be the problem you are having.
    • If you have any features like a waterfall, fountains, solar, etc., make sure you are running the SLAM level FC water through them once or twice a day.
    • Check you skimmer and wear door carefully for signs of algae. The wear door has nooks and crannies algae can hide in, including the tube where the foam goes to keep the top of the door floating at the surface.
    • If you have a removable pool light with a niche behind it, make sure to remove the light and make sure there is no algae hiding in the niche behind it.
    • I've seen once or twice that someone with an above ground, or in ground liner pool had algae on the other side of the liner that was somehow getting through... they didn't find it until they replaced their liner (I don't remember what pool surface you have but I think you mentioned vinyl liner)
Some other questions and comments specific to your situation
  • Have you been noticing progress at all during your SLAM? Has there been a reduction in the amount of algae you see or an improvement in water clarity?
  • Targeting slightly above your SLAM level is fine (i.e. 30, when your target is 28), but too much higher is really just a waste of money because the FC will burn off in the sun faster than it kills the algae because your CYA is no longer protecting it. The people targeting FC levels much higher than their SLAM level are usually the people complaining that they are spending excessive amounts of money on chlorine and not clearing the algae any faster. It's ok if your FC level dips a bit below SLAM target while you are at work, just bring it back up as soon as you get home.
  • With the TFP method it's better if you measure your chemical additions, yes this may mean you are only using a partial bag. I use plastic measuring cups for wet and dry chemicals, other people use a kitchen scale for dry and plastic measuring cup for wet, other people approximate based on % of the container (i.e. if pool math says you need 0.5 pounds of Cal Hypo and it comes in 1 pound bags, adding about half the bag is close enough)
  • Not related to your SLAM, but I believe you said you have a vinyl liner pool and do not test CH because it's not relevant to a vinyl pool. While this is partially true I do want to clarify this. For vinyl pools, there is no minimum CH, so areas with low CH in their fill water often don't test CH very often. That said, high CH levels can cause scaling problems in any pool type. Since you are using Cal Hypo as your FC source and Cal Hypo adds Calcium along with the FC, I do recommend that you test CH (Calcium Hardness) periodically to make sure it does not get too high. Testing CH once every couple weeks, or once a month is probably plenty, but you should have a general idea what it is to prevent scaling.
  • I think you also mentioned your CC has been testing at 0.2 or less... This tells me that you are using the 25ml test for FC. You can save money on test chemicals and still retain plenty of accuracy by using a 10ml water sample and a single scoop of powder when testing FC/CC. Doing it this way, each drop is 0.5, so count the drops to clear then divide by 2 to get your FC level. With a target of 28 FC for your slam this will likely improve your testing accuracy since you will be using fewer drops to achieve your result (and therefore reducing testing error)
Thank you for this thorough review. Even after reading the SLAM article, all this discussion has really helped me understand all the points better. What was totally new to me was the need to test for CH and a better understanding of FC needed to SLAM, which i understood as a minimum and i thought that chlorine should not fall BELOW that number. I am still a little puzzled because my starting post said that i could not get rid of my algae although maintaining a very high FC level and i was told that if i did not SLAM i was not really killing the algae:

"You’re never really killing the algae completely, you just knock it back and then it regrows."

but later, when i said, i was keeping the FC a bit higher than recommended so it didnt slip below the target amount during the day,
i got the following advice from Donldson:

"Algae is killed at any chlorine level, SLAM is just the optimal level above which there is diminishing returns on kill rates and increased risk to liners and equipment. I'm not sure where the misconception that algae doesn't die below SLAM level came from, if that were the case we couldn't maintain clear water at normal target FC/CYA ratios..."

So, i am still a bit confused as to why the algae never dies completely if a lower FC level should work.

I will try the liquid chlorine next season and see how it goes.

Thank you everyone for your time and patience. Hoping to see with an OCLT is the algae really is dead.

One problem remains - which no one responded to is - how can i tell if i have chlorine loss overnight if i am having so much trouble getting an accurate reading:

as i said in a previous post: "I cannot see if i pass an overnight Chlorine loss test because since my chlorine is so high, when i test the same water sample in succession i get different results. i called taylor and asked what is wrong with their kit - i keep getting different results and he told me that a 10% difference is normal. So with chlorine over 30ppm, i may have a reading once of 33 and then next of 36ppm etc. So its really hard to know if i am losing a bit of chlorine overnight. But otherwise pool is clear, no combined chlorine (or .2cc) and the issue continues to be that when i brush a see a bit of yellow dust cloud into the water and i want it GONE. from past experience, if i let go for a day or two it will spread and spread..."
 

Chaya

Well-known member
Jul 28, 2019
50
Lakewood, New Jersey
Ok, so the pool is closed as of last Sunday. The reason I wanted it closed now is because the leaves are starting to fall and it becomes unproductive if multiple leaves are at the bottom of the pool using up the chlorine. As I said, I'm not sure now that my problem is MA or pollen so I'm thinking it's pollen. As for lowering the chlorine level, all advice I see says before closing, to properly balance the water. Closing with my level at 25ppm isn't properly balanced. Also, the winter kit I use has a chemical (don't remember which one) that requires the chlorine to be lower than what mine was before adding it. As for the liquid chlorine, the main reason is because using 3 inch tabs in my chlorinator adds Cyanuric Acid to the pool water. I use tabs at the beginning of the season to help get my CYA up to level, then I switch to liquid chlorine. Also, I used to shock with calcium hypochlorite and I found that using the cheaper powder, it would seemingly not fully dissolve and I would get cloudy water or grainy material on the pool bottom. I only use liquid now and my work has been a lot less. I don't have to add it daily, more like twice or three times weekly to keep my level good. I never got a reply about the chlorine lowering chemical though so I closed the pool with a high level. Don't think it will do any harm but who knows what the pools going to look like when I open it.
Thanks for all the input. i hope to try liquid chlorine next season. please let me know how the pool looks when you open it. when it says to have balanced water, i was not thinking of FC that was too high - i thought it meant proper TA, PH and FC at least target, no CC.
 

aeh0603

Well-known member
Apr 6, 2016
237
San Diego, CA
"You’re never really killing the algae completely, you just knock it back and then it regrows."

but later, when i said, i was keeping the FC a bit higher than recommended so it didnt slip below the target amount during the day,
i got the following advice from Donldson:

"Algae is killed at any chlorine level, SLAM is just the optimal level above which there is diminishing returns on kill rates and increased risk to liners and equipment. I'm not sure where the misconception that algae doesn't die below SLAM level came from, if that were the case we couldn't maintain clear water at normal target FC/CYA ratios..."

So, i am still a bit confused as to why the algae never dies completely if a lower FC level should work.
I went back and re-read your first post and I believe the comment about never really killing the algae and needing to SLAM to kill it was in reference to the process you used to use of throwing some shock in and the water was clear the next day. This old process (frequently advised by pool stores) does not ensure the algae is fully killed and simply knocks it back a bit only to reappear later. The key to a proper SLAM is the M... maintaining the proper FC per your CYA until all 3 criteria are met. This is what ensures you actually kill all the algae. Yes, in your first post you also mentioned your FC was above 30, but I do not think it was understood by everyone that you were currently using the SLAM Process.

One problem remains - which no one responded to is - how can i tell if i have chlorine loss overnight if i am having so much trouble getting an accurate reading:

as i said in a previous post: "I cannot see if i pass an overnight Chlorine loss test because since my chlorine is so high, when i test the same water sample in succession i get different results. i called taylor and asked what is wrong with their kit - i keep getting different results and he told me that a 10% difference is normal. So with chlorine over 30ppm, i may have a reading once of 33 and then next of 36ppm etc. So its really hard to know if i am losing a bit of chlorine overnight. But otherwise pool is clear, no combined chlorine (or .2cc) and the issue continues to be that when i brush a see a bit of yellow dust cloud into the water and i want it GONE. from past experience, if i let go for a day or two it will spread and spread..."
I guess I wasn't super clear, but I was trying to address part of this question when I said the following (the point I was trying to make is that the variance in your test results is most likely caused by technique since you are still learning. Improving your technique when testing will make your results more consistent):

I think you also mentioned your CC has been testing at 0.2 or less... This tells me that you are using the 25ml test for FC. You can save money on test chemicals and still retain plenty of accuracy by using a 10ml water sample and a single scoop of powder when testing FC/CC. Doing it this way, each drop is 0.5, so count the drops to clear then divide by 2 to get your FC level. With a target of 28 FC for your slam this will likely improve your testing accuracy since you will be using fewer drops to achieve your result (and therefore reducing testing error)
When you are testing FC in the 20-30 range using the 25 ml sample that means you are counting 100-150 drops.
When you are testing FC in the 20-30 range using the 10 ml sample that means you are counting 40-60 drops.

One of the easiest ways to get a more accurate result is to minimize your sources of error... you are much less likely to make a mistake counting 60 drops than you are counting 150 drops, any variation in drop size will not impact your results as much, and you will also use less reagent thus saving you money too. I recommend switching to using a 10ml sample size for your FC test. Even at lower FC levels, the 10 ml test is plenty accurate for balancing your pool water. Also, make sure you are holding the reagent bottle vertical (not at an angle) and make sure you let the drops fully form on the tip when dispensing. This will help keep your drop sizes the same and reduce variance in your testing.
 
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aehaas

Member
Sep 30, 2019
8
Sarasota, FL
More people here should invest in a photometer for accurate readings. If you are at this web site then you are clearly more interested in doing it right. As a biochemist I prefer as accurate a reading as possible. I use : Pool eXact® EZ Photometer
It is available as a kit with all the reagent strips for a hundred more dollars or so. Although it only reads chlorine to a level of 12.0 you can read any level by dilution. A 3:1 dilution with distilled water will give you a range of 36 and it will be very consistent in my experience. Just use, clean and maintain the test cell as directed.

AEHaas
 

Donldson

TFP Expert
LifeTime Supporter
In The Industry
Jun 12, 2009
3,943
NW Ohio
More people here should invest in a photometer for accurate readings. If you are at this web site then you are clearly more interested in doing it right. As a biochemist I prefer as accurate a reading as possible. I use : Pool eXact® EZ Photometer
Digital meters in that price range are certainly not very accurate. I would hate to think you are confusing precision for accuracy, that it shows a number to the hundredths place does not mean it actually measures to such a place. Nor is it ever necessary to obtain such specific numbers in a swimming pool. There are many examples on this site of people struggling with inaccurate digital meters, I would recommend you look in to these threads. We do not recommend testing supplies blindly, we do so because they are reliably accurate and precise at a price that makes sense. I can't imagine why anyone would suggest spending 4 times more on a less reliable testing method...
 
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aehaas

Member
Sep 30, 2019
8
Sarasota, FL
My photometer as listed above is accurate at the L1 level, for example, as documented below, for chlorine levels as shown. The meter comes with a standard that can be used to calibrate at any time. I tested the calibration months ago when I purchased the meter and again, after hundreds of tests, last week. Both tested at 1.8 so I am thinking the meter is very stable, accurate and precise.

I have spent hundreds of hours on this and other web sites to learn as much as I can about pools. It's hard to master. I learned a great many things experimenting with my meter and my pool. I enjoyed it. I do these sort of things. 'A new hobby perhaps?

As a biochemist I am picky about testing and measurement. I also do electronics. This meter seems to work well enough for me.

AEHaas

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