Acuracy of Salt Test Strips

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J

JookyDFW

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Jun 17, 2010
29
Hello all,

I just finished adding 600lbs of salt to my pool in preparation for hooking up my SWG. I calculated I would need around 720lbs to get my pool up to the 3500ppm salt level needed for the SWG. I used an accutest strip to test the salt level after the salt had disolved into the water and got a result of 4.6 which equalls 1480ppm. give the amount of salt and my estimated pool volume of 25k gallons I was expecting a number about twice that. The salt I used was 10 bags of blue bag water softener salt from Home Depot and 5 white bags of pool salt from Home Depot. All bags were 40lbs for a total fo 600lbs. My readings as of Friday (7/22) evening are:

FC: 4.5
TC: 4.5
PH: 7.8
ALK: 100

CYA has been hovering around 50 and I have not had to add much water so I expect it hasn't changed much. These numbers are a little off from the pool schooll ideal numbers so I was wondering if they can affect the test strip reading. Or can these test strips have inaccurate results?

Roland
 
I didn't have a way to isolate my main drain so one problem is that the salt is heavier than the water and so the salinity of the bottom of the pool is higher and won't get pulled up by skimmers. Just hooked up my pool vac and left it on the bottom overnight which improved my readings significantly. You can test this by measuring the "instant salinity" when you put the pool vac in if you have your SWG hooked up already. Mine jumped about 1000 ppm.
 
First I would brush the pool to ensure the salt has dissolved and mixes.

Second, the salt test strips are easy to mis-read. You want to read the tip of the white mark. I use a magnifying glass to ensure that I do not underestimate the height of the white line. My readings of the test strips have been within +- 200 of the salt level indicated by my SWG.
 
@JasonLion:

Thanks for the quick response. I think I may have tested it too early as you suggested. I tested again this morning without having added any salt and it was up to around 5.8 (2400ppm). A 1000ppm improvement. I had some guests over yesterday who might have helped stir up the water a little too. I just got another 240lbs of salt which should be enough to get me where I need to be. Based on my calculations (4ppm per lb) I will need 300lbs to get me to 3600ppm.

@Gaidal:

Thanks for the suggestion to shut off the skimmer. I'll give it a try and see if that helps.

RTS
 
So I finally got the salt generator up and running. After adding about 840lbs of salt total and waiting two days after the last bages were disolved I took a test reading. The strip read 4.8 which corresponds to about 1920ppm. I started up the Compupool CPSC24 and got it going. This unit tests for salt level and is giving a reading of 5100-5200ppm. So I 'm not sure which reading to believe. I'm inclined to believe the salt generateor because the water tastes real salty. I've heard that if salt levels are above optimal (3500ppm for this unit) that I should drain and refill to get the correct levels. What is the down side to leaving the level higher?
 
My experiance with the Compupool has been that it reads very high, however adding 840 # to a pool that I expect to be less than 2000 gals. would raise the salt level pretty high. How old are your salt strips? At the moment I am using the Taylor drop test but when I was using salt strips they both read pretty close. I would get another batch of strips or the Taylor drop test and see which reading is closer.
 
840 pounds of salt added to a 25,000 gallon pool will increase the salt level by 4,000 ppm. Most fill water already has some salt, so you're going to be above 4,000 ppm.

You should take a sample of your pool water and your fill water to a pool store to have them tested with a salt meter.
 

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I have an update on this issue. When I got home last night I checked the SWG and the "over salt" light had come on. I think there are two problems. First, I think the salt test strips are bad. Thanks Leslies. Second I think my pool may not be as big as I think it is.

To make things worse, the city has just announced stage 2 water restrictions. I think this is more for the people with sprinkler systems. In 2007 there were water restrictions and I had to refill the pool after the liner was replaced. I had to get approval by the city before getting any work done. A person with the city told me that the 20k+ water it would take to fill my pool was nothing compared to the amount of water used by sprinkler systems. Maybe I could divert my return line to water my lawn for a few days.
 
franke said:
My experiance with the Compupool has been that it reads very high, however adding 840 # to a pool that I expect to be less than 2000 gals. would raise the salt level pretty high. How old are your salt strips? At the moment I am using the Taylor drop test but when I was using salt strips they both read pretty close. I would get another batch of strips or the Taylor drop test and see which reading is closer.
Click to expand...

Test strips are a couple weeks old. No telling how long they were sitting on Leslie's shelf. I guess I should check for an expiration date.
 
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