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Thread: testing with strips

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    testing with strips

    I personally use test strips. After having done hundreds of strip tests and probably hundreds of drop tests with our Lamotte Colour Q at the store, strips are not as evil as pretty much everyone on here makes them out to be.
    How much fun is it to use your Taylor test kit everyday, awfully time consuming i would imagine and tiresome after awhile.
    I use strips daily and having a good idea of exactly where my pool and hot tub are 'at' i can make quick changes in under 5 minutes, of course if I need to really nail it down i use the Colour Q.

    I dont get why everyone here has got a hate on for test strips. Do I use them exclusively? no. Do they have their place in water chemistry? I think so.
    I believe in 'balance', i cant honestly tell someone that the ONLY way to test their water is by using one of these test kits, they would shop elsewhere guaranteed. I tell our customers that if they are having problems balancing their water then to bring in a sample and we will test it and get them back on track.

    I always have a hard time believing anything or anyone that says their is only one way to do things properly.

    This just seems to be one of those things that forums in general always have, one way of thinking, regardless of anything else.

    There I said it.
    Blessed is the man who can laugh at himself for he will never cease to be amused.
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    Re: testing with strips

    Most people who come on here for the first time are either new pool owners or they have some sort of problem with their water chemistry, or have algea. The great majority of them also have a CYA level that is very high due to over use of pucks. Another issue is a pH that is not stable. This can be an issue with the TA, especially if they have a SWCG where the TA needs to be adjusted to 70-80 ppm. This adjustment requires a more sensitive test. Test strips are not accurate enough to measure the CYA, TA, etc in such a way as to help fix the problems that new, or even long time pool owners encounter when switchng to the BBB methods. In addition, proper shock procedures of a pool require the accurate measurement of the FC and FC loss during the process. This can only be accomplished by using a FAS-DPD test, not strips.
    The the Colour Q kit only goes to 10 ppm on the FC test, so it's pretty limited when trying to shock. The CYA test is a little tricky too (more so than the "dot" test in the Taylor or TF100 kit). The CH test is not as accurate either.

    I suppose if you want a quick and dirty reading, strips would be ok, but then again, pH and FC are fairly easy and quick to do. I can do a pH and a FAS-DPD test in less than 5 minutes and I know exactly what my numbers are. As far as the CYA, TA, and CH test, those dont get run as much. I test those once a month, TA maybe 2 times a month, but thats it. IMO, strips are pretty useless. If someone really wants to take care of their water and ditch the pool store, then a good test kit is a good investment and can actually save someone the price of the kit over the course of half a swim season.

    Quote Originally Posted by thecanuck22
    I tell our customers that if they are having problems balancing their water then to bring in a sample and we will test it and get them back on track.

    .
    With all due respect, thats the idea of BBB and testing with a good kit. If people did that, they wouldnt need the pool store to get them "back on track". In fact, they wouldnt need the pool store at all!
    14,000 gallon IG, Vinyl. Hayward 3/4 hp superpump, Penatair IC40 SWCG, Pentair automation, Hayward sand filter, Aqua Comfort heat pump, Hayward 400k Lo-Nox LP heater.

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    Re: testing with strips

    I hear ya, I personally have a Taylor 2005 kit myself which does everything I need it to do. I have been thinking of getting some strips and do some comparisons back to back so I know what I am looking at when I use the strips. I've got my pool down to a science and test once a week at best, I add the same amount of bleach everyday (sometimes double it for every two days when I am on the road) and the same amount of MA every week and its always bang on. I've learned what lots of rain will do and how less FC I lose when the cover is kept on and recently learnt how much less FC I lose when I let the pool cool down during the week and only start heating on Friday for the weekend. I can almost tell how much chlorine is in the pool by how it smells when I remove the cover.

    I'm giving the evil strips a try too, got any good recommendations for a mfg?
    55 Kilolitre in-ground 18'X36' vinyl lined kidney shape, 1HP pump, Jacuzzi 250lb sand filter, RayPak Delta T 200K BTU natural gas heater. New PoolWerks "Blue Diffusion" liner on May 26th-2011
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    Re: testing with strips

    I guess i never thought that when using the taylor kit that you dont do a full test all the time, sometimes pH sometimes other things.
    I do understand the difficulties that are there when people first learn about the information from sites like this and doing a complete and very accurate test is the best way to really understand what is truly going on. Past that though when you have a firm grasp on your chemistry, using a test strip is a very fast and accurate enough method until your next drop test. Strips are consistent I find and once you get the color readings down by also using the drop test, ie. this shade of orange is 'around' 7.6-7.8, that you know to add some acid to bring it down and so on.

    As far as a mfg 4Jaw, it really doesnt matter as long as it is a quality strip usually only available at a PS. I have used two different mfg's strips for long periods of time. One before i worked at a PS and then I switched to our stores brand, it took some getting used to because its a different strip but I got used to the readings.
    I currently use the Lamotte brand and am happy, but i was happy with the other brand as well.
    Blessed is the man who can laugh at himself for he will never cease to be amused.
    To teach is to learn twice.
    My Pool. 20 x 40 120,000 litres (about 30k gal) sand filter, a pump of some type...lol & a bunch of neighbourhood kids.

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    Re: testing with strips

    Quote Originally Posted by thecanuck22
    Past that though when you have a firm grasp on your chemistry, using a test strip is a very fast and accurate .
    They may be fast, but I would not describe them as in any way accurate. Proper testing of pool water is the only way to have pool thats trouble free and freedom from the pool store. I'll reiterate. With a proper test kit, the pool store becomes irrelevent.
    14,000 gallon IG, Vinyl. Hayward 3/4 hp superpump, Penatair IC40 SWCG, Pentair automation, Hayward sand filter, Aqua Comfort heat pump, Hayward 400k Lo-Nox LP heater.

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    Re: testing with strips

    Simply browsing this forum should give you a clear idea of the stunning inferiority of test strips over drops based testing. To argue that well-documented issue in favor of strips is, well, almost irrelevant.

    The vast majority of members here on the forum are residential pool owners.......convenience and profitability are not a consideration. Cannuck, your use of strips and charging people for that information is not allowing you to put your best foot forward. As a professional, you should be concerned about providing professional results.
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

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    Re: testing with strips

    Just looking at the sheer number of posts that post strip results and then drop kit results and seeing the difference between the two is enough to shy me away from using strips.

    My own experience with striips is classic. One example is my CH and CYA numbers. The strips showed my CH as 250 and when I got the TF-100 I found that it was less than 20ppm. I got an assay on the water here and it confirmed the llower number. The strips showed my CYA being 20-50 before I ever added any to the pool.
    Dave J. TFP Moderator
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    Re: testing with strips

    Maybe a month after I moved in to my house I was buying some stuff at Lowes and stopped by the pool section to get a brush. All that was left here was a pole and a leaf skimmer. I saw the test strips and bought them.

    The most natural thing to do is to dip the strip then lay it on the plastic color chart to match colors. But then the water tends to move around via surface tension, and the different sections bleed together and the colors are all wrong.

    It also make a difference how long one waits to take the reading. Do you use a stopwatch or count? Counting is inaccurate, even using one-alligator, two-alligator. The colors can change during the count. And after the 15 seconds, the colors start to fade again.

    Then there's the limit. Knowing that CH is at the end of the scale is not accurate. Is it right at the end, or twice that number, or ten times that number?

    Some days I'd test three times and not get the same readings and these are from the same batch of strips!

    Finally, the pool service that was taking care of things used strips. Which is probably why it took 10 lbs of dry acid and a gallon of MA to move pH down below 8. Which is probably why my two-year old plaster has calcium scale.

    With my TF100 and my speedstir, I can run all the tests in 10-15 minutes. I don't mind the time; I sit at the patio table with my coffee and cigarettes and relax. Things are pretty stable, so I don't run all the tests all the time, and then it takes even less time. And there's no anxiety because some number suddenly jumped - which it didn't, but the test strip indicates it did.
    16K freeform gunite with spa; Pentair 4000 DE filter; Century Whisperflow 1 HP; Pentair Minimax heater.
    Troublefree does not mean Maintenancefree. It's like brushing your teeth: You can spend a couple minutes a day and pennies a week or go to the dentist once a year and spend several thousand dollars.
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    Re: testing with strips

    I sand and prime before I paint. I warm up the car before I change the oil. I edge the lawn before I mow. I skim my pool before I go in, and I take a shower before I go to bed!

    To me, it is all about doing the best job that I can and taking pride in what you do. Short cuts never produce prideful work, in my opinion. I'd rather have hard facts than guessing what I have to deal with.

    I don't have such a busy day that cutting corners is going to make up time! I'll take the extra couple of minutes to do the job right, and know I did my best. Helps me to sleep at night after that shower!

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    4JawChuck's Avatar
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    Re: testing with strips

    In my job test strips are a fact of daily life, solution testing for medical equipment cleanliness is standard across the industry for many solutions. My customers use them daily and trust them to provide accurate results, most of the issues I have seen are due to incorrect reading or storage in a humid location or simple operator error. If you have ever had a medical procedure the equipment sterility was tested with a test strip, these people don't have time for drops and judgement errors from reading colors by different personnel.

    I see Lamotte has a wide range test strip which would be perfect for me (since I usually only test PH and FC daily), I'm going to check them out and test them back to back with my Taylor kit.



    Stay tuned.
    55 Kilolitre in-ground 18'X36' vinyl lined kidney shape, 1HP pump, Jacuzzi 250lb sand filter, RayPak Delta T 200K BTU natural gas heater. New PoolWerks "Blue Diffusion" liner on May 26th-2011
    Avatar is my pool!

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    Re: testing with strips

    As far as I know, there are no test strips available to consumers for pools/spas that test for Calcium Hardness (CH). Test strips can only test for Total Hardness (TH) which includes magnesium in addition to calcium and is irrelevant with regard to the saturation index since scaling occurs with calcium carbonate, not with magnesium (at levels found in natural water) and it is saturation with calcium carbonate that protects dissolving/pitting of plaster.

    In addition to the lack of a CH test, the CYA test strip seems to be the most problematic and inconsistent. Also, the resolution and accuracy of test strips compared to the drop-based test isn't even close as you can see below (though LaMotte has added some wider range chlorine tests recently that I also describe after the table):

    ....................................... <---------------------------------- TEST STRIPS -------------------------------------> . <--------------- DROP-BASED ---------------->
    ........................................ LaMotte Insta-Test 6 .......... Taylor sureTrack 6 ....... AquaChek Select/7-way ........ Taylor K-2006 .............. TFTestkits TF-100
    Free Chlorine (FC) .......... 0, 0.5, 1.0, 3.0, 5.0, 10 ........ 0, 1, 2, 3, 5, 10 ........... 0, 0.5, 1.0, 3.0, 5.0, 10.0 ....... every 0.2 ppm* ............. every 0.2 ppm*
    Combined Chlorine (CC) ..... calculate from TC-FC ......... not available ................ calculate from TC-FC .......... every 0.2 ppm* ............. every 0.2 ppm*
    Total Chlorine (TC) ......... 0, 0.5, 1.0, 3.0, 5.0, 10 .......... not available ............. 0, 0.5, 1.0, 3.0, 5.0, 10.0 ...... calc. from FC+CC .......... calc. from FC+CC
    pH ................................. 6.2, 6.8, 7.2, 7.8, 8.4 ... 6.4, 6.8, 7.2, 7.5, 7.8, 8.4 ..... 6.2, 6.8, 7.2, 7.8, 8.4 .... 7.0, 7.2, 7.4, 7.6, 7.8, 8.0 .. 6.8, 7.2, 7.5, 7.8, 8.2
    Total Alkalinity (TA) ...... 0, 40, 80, 120, 180, 240 .... 0, 40, 80, 120, 180, 240 .. 0, 40, 80, 120, 180, 240 ...... every 10 ppm ................ every 10 ppm
    Calcium Hardness (CH) ......... not available .................... not available .................... not available .................... every 10 ppm ................ every 10 ppm
    Total Hardness (TH) ......... 50, 100, 250, 450, 800 ..... 0, 100, 200, 400, 800 .... 0, 100, 250, 500, 1000 ... not available (or needed) .. not available (or needed)
    Cyanuric Acid (CYA) .......... 0, 40, 100, 150, 250 ..... 0, 30-50, 100, 200, 300 ... 0, 30-50, 100, 150, 300 .... 30-100 every 10 ppm ... 20-100 every 10 ppm

    *The resolution is dependent on sample size where a 10 ml sample has 0.5 ppm, a 25 ml sample has 0.2 ppm.

    The newer wide-range test strips (Wide Range Total Chlorine & pH - click on Specialty Test Strips tab) measure 0, 1, 5, 10, 20, 50 ppm Total Chlorine (not Free Chlorine) and 4, 5, 6, 7, 8, 9, 10 for pH.

    A doubling of Total Alkalinity (TA) from 40 to 80 ppm (at a CYA level of 30 ppm) increases the saturation index by 0.37 which is large and not insignificant. A doubling of Calcium Hardness increases the saturation index by 0.3, though you can't even measure this with test strips (you can only measure Total Hardness which prevents you from calculating a real saturation index). A change in pH on the test strips of 0.4 is twice as large as that measured in the drop-based test of 0.2 and affects the saturation index by these same amounts. A misreading on test strips of a pH of 7.8 as 7.2, a TA of 80 as 40, and a CH of 250 as 100 (assuming you could even measure CH with test strips, which you can't), is an error in the saturation index of over 1.3 -- even a half-way misread would still be an error of nearly 0.6. A misreading with drop-based tests of the pH of 7.8 as 7.6, a TA of 80 as 70, and a CH of 250 as 240 is an error in the saturation index of under 0.3. If one has a vinyl pool with no need for calcium carbonate saturation and the CH is known to be low, then this error is not a problem.

    Since the active chlorine level is roughly proportional to the FC/CYA ratio, with test strips a misreading of an FC of 3.0 as 5.0 and a CYA of 100 as 40 misreads an FC/CYA ratio of 0.03 as 0.125 which is a huge error that can lead to algae growth. With drop-based tests even using the 10 ml sample size, a misreading of an FC of 3.0 as 3.5 and a CYA of 100 as 80 misreads an FC/CYA ratio of 0.03 as 0.044 which is not that much of an error and would alert one to too low an FC relative to the CYA level.

    One cannot do an accurate overnight chlorine loss test with test strips, especially when shocking the pool.

    The drop-based test kits are easier to see as well since the FAS-DPD chlorine test goes from pink/red to clear as you add drops. The TA test transition from green to red is easy to see. The CH transition from red to blue is more difficult. The CYA turbidity test can also take a little getting used to.

    Once you know your pool you usually test mostly chlorine and possibly pH so I can see that once you get to that point you can use test strips for a quick check if you've calibrated such measurements against a more accurate test, but should still probably do a more accurate verification (of chlorine and pH) once a week or so just to be sure. However, if you are keeping your pool on the edge of a minimum FC relative to the CYA level, the test strips could throw you off.

    Richard
    16,000 gallon outdoor in-ground 16'x32' plaster pool; Pentair Intelliflo VF pump; Pentair IntelliTouch i9+3s control system; Jandy CL-340 square foot cartridge filter
    12 Fafco solar panels; Purex Triton PowerMax 250 natural gas heater (200,000 BTU/hr output); automatic electric pool safety cover; 4-wheel pressure-side "The Pool Cleaner"

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    Re: testing with strips

    Quote Originally Posted by Richard320
    Maybe a month after I moved in to my house I was buying some stuff at Lowes and stopped by the pool section to get a brush. All that was left here was a pole and a leaf skimmer. I saw the test strips and bought them.

    The most natural thing to do is to dip the strip then lay it on the plastic color chart to match colors. But then the water tends to move around via surface tension, and the different sections bleed together and the colors are all wrong.

    It also make a difference how long one waits to take the reading. Do you use a stopwatch or count? Counting is inaccurate, even using one-alligator, two-alligator. The colors can change during the count. And after the 15 seconds, the colors start to fade again.

    Then there's the limit. Knowing that CH is at the end of the scale is not accurate. Is it right at the end, or twice that number, or ten times that number?

    Some days I'd test three times and not get the same readings and these are from the same batch of strips!

    Finally, the pool service that was taking care of things used strips. Which is probably why it took 10 lbs of dry acid and a gallon of MA to move pH down below 8. Which is probably why my two-year old plaster has calcium scale.

    With my TF100 and my speedstir, I can run all the tests in 10-15 minutes. I don't mind the time; I sit at the patio table with my coffee and cigarettes and relax. Things are pretty stable, so I don't run all the tests all the time, and then it takes even less time. And there's no anxiety because some number suddenly jumped - which it didn't, but the test strip indicates it did.
    I wish the TF100 came with better instructions!
    4' X 6' depth 10.3 k IG Gunite w/blue diamond brite interior finish. Pentair 1.5 HP pump, Goldline salt system, 300,000 btu Pentair gas heater, Pentair FNS DE filter, blower for in pool bench spa jets, floor sweep/cleaning system, bird cage covering, highly filtered well water.

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    Re: testing with strips

    Quote Originally Posted by Fastsporty77
    I wish the TF100 came with better instructions!
    Anything in particular giving you an issue? Below is a link to the TF intructions

    http://tftestkits.net/Test-Kit-Instructions-10.html
    24'x52" AGP (13,500 Gallons), Intex SWG, (2)Solar Bear 4x20 panels, Hayward S220T Filter, 1/2hp Pentair Superflo

    Pool School, TFTestKits, Pool Calculator

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    Re: testing with strips

    Quote Originally Posted by Fastsporty77
    Quote Originally Posted by Richard320
    Maybe a month after I moved in to my house I was buying some stuff at Lowes and stopped by the pool section to get a brush. All that was left here was a pole and a leaf skimmer. I saw the test strips and bought them.

    The most natural thing to do is to dip the strip then lay it on the plastic color chart to match colors. But then the water tends to move around via surface tension, and the different sections bleed together and the colors are all wrong.

    It also make a difference how long one waits to take the reading. Do you use a stopwatch or count? Counting is inaccurate, even using one-alligator, two-alligator. The colors can change during the count. And after the 15 seconds, the colors start to fade again.

    Then there's the limit. Knowing that CH is at the end of the scale is not accurate. Is it right at the end, or twice that number, or ten times that number?

    Some days I'd test three times and not get the same readings and these are from the same batch of strips!

    Finally, the pool service that was taking care of things used strips. Which is probably why it took 10 lbs of dry acid and a gallon of MA to move pH down below 8. Which is probably why my two-year old plaster has calcium scale.

    With my TF100 and my speedstir, I can run all the tests in 10-15 minutes. I don't mind the time; I sit at the patio table with my coffee and cigarettes and relax. Things are pretty stable, so I don't run all the tests all the time, and then it takes even less time. And there's no anxiety because some number suddenly jumped - which it didn't, but the test strip indicates it did.
    I wish the TF100 came with better instructions!
    What do you feel is missing, Fastsporty77? I use the TF100 every day, and find it easy (I even have most customers follow along as I do my tests) to understand and use (honestly, unlike the Taylor kit-I have a K2006 also). I'm sure we can get you some help here with any problems you might be having.

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    Re: testing with strips

    Quote Originally Posted by Fastsporty77
    I wish the TF100 came with better instructions!
    There's Water Testing Instructions on One Page as well as Extended Test Kit Directions.
    16,000 gallon outdoor in-ground 16'x32' plaster pool; Pentair Intelliflo VF pump; Pentair IntelliTouch i9+3s control system; Jandy CL-340 square foot cartridge filter
    12 Fafco solar panels; Purex Triton PowerMax 250 natural gas heater (200,000 BTU/hr output); automatic electric pool safety cover; 4-wheel pressure-side "The Pool Cleaner"

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    Re: testing with strips

    Quote Originally Posted by chem geek
    Quote Originally Posted by Fastsporty77
    I wish the TF100 came with better instructions!
    There's Water Testing Instructions on One Page as well as Extended Test Kit Directions.
    Thanks I'm a novice to this stuff (not a chemist)and that really helps.
    4' X 6' depth 10.3 k IG Gunite w/blue diamond brite interior finish. Pentair 1.5 HP pump, Goldline salt system, 300,000 btu Pentair gas heater, Pentair FNS DE filter, blower for in pool bench spa jets, floor sweep/cleaning system, bird cage covering, highly filtered well water.

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    Re: testing with strips

    Quote Originally Posted by simicrintz
    Quote Originally Posted by Fastsporty77
    Quote Originally Posted by Richard320
    I wish the TF100 came with better instructions!
    What do you feel is missing, Fastsporty77? I use the TF100 every day, and find it easy (I even have most customers follow along as I do my tests) to understand and use (honestly, unlike the Taylor kit-I have a K2006 also). I'm sure we can get you some help here with any problems you might be having.
    Thanks. Really I opened the box the kits came in and went "Holy J's" as I hate complicated stuff.
    I'll figure it out and ask here when I cannot. Never realised how hard a pool can be to keep stable.
    4' X 6' depth 10.3 k IG Gunite w/blue diamond brite interior finish. Pentair 1.5 HP pump, Goldline salt system, 300,000 btu Pentair gas heater, Pentair FNS DE filter, blower for in pool bench spa jets, floor sweep/cleaning system, bird cage covering, highly filtered well water.

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    Re: testing with strips

    Most of the tests you don't do very frequently and the ones you do regularly get very easy once you've done them a few times. You'll get the hang of it in no time.
    16,000 gallon outdoor in-ground 16'x32' plaster pool; Pentair Intelliflo VF pump; Pentair IntelliTouch i9+3s control system; Jandy CL-340 square foot cartridge filter
    12 Fafco solar panels; Purex Triton PowerMax 250 natural gas heater (200,000 BTU/hr output); automatic electric pool safety cover; 4-wheel pressure-side "The Pool Cleaner"

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    Re: testing with strips

    Quote Originally Posted by simicrintz
    I sand and prime before I paint. I warm up the car before I change the oil. I edge the lawn before I mow. I skim my pool before I go in, and I take a shower before I go to bed!

    To me, it is all about doing the best job that I can and taking pride in what you do. Short cuts never produce prideful work, in my opinion. I'd rather have hard facts than guessing what I have to deal with.

    I don't have such a busy day that cutting corners is going to make up time! I'll take the extra couple of minutes to do the job right, and know I did my best. Helps me to sleep at night after that shower!
    lol yeah i eat my breakfast on my way into work, I listen to my other industries podcasts when i run, i brush my teeth in the shower often and i Edited for politeness. Butterfly. Its also about efficiency. I am proud of the job i do (except for once last week), the education i provide to customers and i too sleep well at night.

    I dont rely on the strips for cya or ch or anything like that, its more of a guidline, but for things like pH Cl and to an extent TA i trust my ability to properly read the strip and make adjustments. I do take water samples back to the store, I am not often wrong in my readings with the strip.

    Its about doing the test in the exact same manner everytime, it does take some getting good at. Many of you dont want to spend the time energy or money to do that, and thats your right. The thing is that people here just label strips as this big evil thing that should never be used and look down the nose at anyone who uses them. I would guess 90% of current spa owners use them, and a large majority of those with no problems.

    The rest of the world uses them. I do too. I use them responsibly.
    Blessed is the man who can laugh at himself for he will never cease to be amused.
    To teach is to learn twice.
    My Pool. 20 x 40 120,000 litres (about 30k gal) sand filter, a pump of some type...lol & a bunch of neighbourhood kids.

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    Re: testing with strips

    Quote Originally Posted by chem geek
    As far as I know, there are no test strips available to consumers for pools/spas that test for Calcium Hardness (CH). Test strips can only test for Total Hardness (TH) which includes magnesium in addition to calcium and is irrelevant with regard to the saturation index since scaling occurs with calcium carbonate, not with magnesium (at levels found in natural water) and it is saturation with calcium carbonate that protects dissolving/pitting of plaster.

    In addition to the lack of a CH test, the CYA test strip seems to be the most problematic and inconsistent. Also, the resolution and accuracy of test strips compared to the drop-based test isn't even close as you can see below (though LaMotte has added some wider range chlorine tests recently that I also describe after the table):

    ....................................... <--------------- TEST STRIPS --------------> .. <------------ DROP-BASED ------------->
    ........................................ LaMotte Insta-Test 6 .......... Taylor sureTrack 6 ........ Taylor K-2006 .............. TFTestkits TF-100
    Free Chlorine (FC) .......... 0, 0.50, 1.0, 3.0, 5.0, 10 ........ 0, 1, 2, 3, 5, 10 ........... every 0.2 ppm* ............. every 0.2 ppm*
    Combined Chlorine (CC) ..... calculate from TC-FC ............ not available ............. every 0.2 ppm* ............. every 0.2 ppm*
    Total Chlorine (TC) ......... 0, 0.50, 1.0, 3.0, 5.0, 10 ........ not available ............. calc. from FC+CC ........... calc. from FC+CC
    pH ................................. 6.2, 6.8, 7.2, 7.8, 8.4 ... 6.4, 6.8, 7.2, 7.5, 7.8, 8.4 .. 7.0, 7.2, 7.4, 7.6, 7.8, 8.0 .. 6.8, 7.2, 7.5, 7.8, 8.2
    Total Alkalinity (TA) ........ 0, 40, 80, 120, 180, 240 .... 0, 40, 80, 120, 180, 240 ... every 10 ppm ............. every 10 ppm
    Calcium Hardness (CH) ......... not available ................... not available ................... every 10 ppm ............. every 10 ppm
    Total Hardness (TH) ......... 50, 100, 250, 450, 800 ..... 0, 100, 200, 400, 800 .... not available (or needed) .. not available (or needed)
    Cyanuric Acid (CYA) .......... 0, 40, 100, 150, 250 ....... 0, 30-50, 100, 200, 300 ... 30-100 every 10 ppm .. 20-100 every 10 ppm

    *The resolution is dependent on sample size where a 10 ml sample has 0.5 ppm, a 25 ml sample has 0.2 ppm.

    The newer wide-range test strips (Insta-Test Wide Range Total Chlorine & pH) measure 0, 1, 5, 10, 20, 50 ppm Total Chlorine (not Free Chlorine) and 4, 5, 6, 7, 8, 9, 10 for pH.

    A doubling of Total Alkalinity (TA) from 40 to 80 ppm (at a CYA level of 30 ppm) increases the saturation index by 0.37 which is large and not insignificant. A doubling of Calcium Hardness from 50 to 100 ppm increases the saturation index by 0.3, though you can't even measure this with test strips (you can only measure Total Hardness which prevents you from calculating a real saturation index). A change in pH on the test strips of 0.4 is twice as large as that measured in the drop-based test of 0.2 and affects the saturation index by these same amounts. A misreading on test strips of a pH of 7.8 as 7.2, a TA of 80 as 40, and a CH of 250 as 100 (assuming you could even measure CH with test strips, which you can't), is an error in the saturation index of over 1.3 -- even a half-way misread would still be an error of nearly 0.6. A misreading with drop-based tests of the pH of 7.8 as 7.6, a TA of 80 as 70, and a CH of 250 as 240 is an error in the saturation index of under 0.3. If one has a vinyl pool with no need for calcium carbonate saturation and the CH is known to be low, then this error is not a problem.

    Since the active chlorine level is roughly proportional to the FC/CYA ratio, with test strips a misreading of an FC of 3.0 as 5.0 and a CYA of 100 as 40 misreads an FC/CYA ratio of 0.03 as 0.125 which is a huge error that can lead to algae growth. With drop-based tests even using the 10 ml sample size, a misreading of an FC of 3.0 as 3.5 and a CYA of 100 as 80 misreads an FC/CYA ratio of 0.03 as 0.044 which is not that much of an error and would alert one to too low an FC relative to the CYA level.

    One cannot do an accurate overnight chlorine loss test with test strips, especially when shocking the pool.

    The drop-based test kits are easier to see as well since the FAS-DPD chlorine test goes from pink/red to clear as you add drops. The TA test transition from green to red is easy to see. The CH transition from red to blue is more difficult. The CYA turbidity test can also take a little getting used to.

    Once you know your pool you usually test mostly chlorine and possibly pH so I can see that once you get to that point you can use test strips for a quick check if you've calibrated such measurements against a more accurate test, but should still probably do a more accurate verification (of chlorine and pH) once a week or so just to be sure. However, if you are keeping your pool on the edge of a minimum FC relative to the CYA level, the test strips could throw you off.

    Richard
    dude you love to complicate things eh? I wish i had the energy to read that post. Do you just cut and paste from a word file or do you actually spend that much time writing out a very complicated response? i see long replies like this one all the time from you, just wondering.
    Blessed is the man who can laugh at himself for he will never cease to be amused.
    To teach is to learn twice.
    My Pool. 20 x 40 120,000 litres (about 30k gal) sand filter, a pump of some type...lol & a bunch of neighbourhood kids.

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