Aquacheck Salt Strips way off?

[bluenoise]

Hi, gang-

I have a Goldline SWG with the T-15 cell and have been having ongoing problems with it reporting low salt. It will read 2300 ppm when the Aquacheck salt strips report 3360 ppm. I have tried cleaning the cell, done the dilute MA cleaning (no bubbles) and checked water flow and everything seems right. Recalibrating doesn't hold the expected reading. The folks at Goldline told me it sounds like a bad cell, so a tech came out today. Unfortunately, I wasn't home to talk to him, but my wife told me he checked everything out and the only thing he found wrong was the pool needs about 125 pounds of salt. I just reran the salt test now that I'm home and the strip read 3360 ppm again. Adding that much salt will push me up by about 1000 ppm, according to the Pool Calculator. My wife said he tested the water with some "fancy device" (her words) and it reported the salt to be low.

It certainly makes sense to me, assuming the test strips are off by 1000 ppm, but I have never heard of these strips being that far off. The expiration date on these strips is Aug, 2009 and they've always been kept dry with their desiccant packet in-place.

If I add the 1000 ppm and my pool is already at 3360 ppm, is that going to push my salt up too high? I don't want to have to replace a bunch of water if his test was wrong, but it does seem to fit the symptoms I was having (Low Salt indicator).

 

[MikeInTN]

I had an issue when I opened my pool with a bad bottle of Aquachek strips. Here's the thread on my troubles. I ended up getting a Taylor K-1722 salt test kit to use to figure out which bottle of strips was lying to me. Turns out it was the older ones . You may need some new test strips.

 

[bluenoise]

Thanks for the link, Mike. It seems you had a very similar experience to what I seem to be having. My wife is out and about right now and picking up salt on her way back, but I won't add it to the pool until I run a water sample down to my local pool store for them to test. The thought of over-salting the pool is worrying me.

 

[bluenoise]

I just returned from the pool store where I had them test my water with an electronic tester and brand new Aquacheck strips. From the same sample of water, here are the results:

- My strip: 3360
- Their strip: 2700
- Their electronic tester: 2400
- My SWG: 2400 (Instantaneous reading)

I've added 50 pounds of salt and will test again with a new strip (I bought a new bottle of strips while there).

The pool tech yesterday and the pool store guy both claim the electronic tester is far more accurate than the strips. By everything I've read so far, the strips are supposed to be very accurate, too. So, which is it? Would I be better off buying a tester for ~$100 or keep buying strips at $13/10 tests based on accuracy and cost?

 

[duraleigh]

The Aqua Chek strips, overall, seem very, very predictable and accurate.

It's one of the few items I sell in addition to the testkit and, to this point, we have had no complaints (I believe this is true.....not 100% certain it's zero)

We have sold enough of them to make me think they are pretty trustworthy.

Waterbear has tested pools as a profession and is a firm believer in the strips and not a firm believer in the electronic testers (affordable ones, anyway)

 

[Guest]

The strips are as dependable as the Taylor drop test and much more likely to be done correctly!
However, moisture and light are their enemy. Keep them inside in a dry place.
Electronic testers are fine IF (and it's a bit IF) you keep them calibrated. In just one week many of them will drift enough to give you results that are off. Also, many of them are very temperature dependant, even more so than some of the conductivity sensors in the SWGs!

With all testing materials a bad batch can come through. However, Taylor seems to be a bit better at quality control than either LaMotte or Hach (Aquachek). This is one of the main reasons that I recommend Taylor kits over LaMotte!

 

[frankgh]

I bring a bottle of water to my pool store when I have to go there for something else like a new skimmer net etc. They test salt with an electronic tester that was way off what my new test strips were reading. I asked when they had last calibrated their tester and they admitted it "had been some time ago". I was back the other day and their tester is now right on the money with my test strips, 3400.

My AquaRite will read 2800 and I can "recalibrate" it so it is back up to 33-3400 but it will drift down over a day or so. It is running at 40% 10 hours a day and FC is always 2.0 at the end of a blistering, sunny day so, I don't really care what the control unit says, it is putting out CL and the pool looks great! There are some AquaRite experts here who could explain why it is not a very accurate reading, just trust your up to date, stored properly test strips.

 

[jagfan]

It is running at 40% 10 hours a day and FC is always 2.0 at the end of a blistering, sunny day so, I don't really care what the control unit says, it is putting out CL and the pool looks great!

Wow, you're in FL and can keep your FC at 2 without problems? Wish I could keep my FC at a lower level. I have to keep mine at 6-7 or algae will take over. I recently added a SWG and last week my pool cage was completed so perhaps I'll be able to adjust my FC level as all that trash won't be getting into the pool.

 

[Brad S]

Someone will correct me if i'm wrong, but the SWG will make chlorine over a fairly large range of salt concentrations. My intellichlor will make chlorine from as low as 2500 ppm. It doesnt really matter if the salt meter on the unit "drifts". They will generate over a wide range. That being said, they tend to be more efficient i think right around 3300 ppm or so, depending on the brand and model, at least thats what i can read and hear. I still dont know exactly why. Mine has consistently measured low this year. My Aquacheck strips are right at 3200 ppm (i ckecked last night) and the SWG says 2650 ppm. Assuming a 300 -400 ppm error in the generator reading and a 200 ppm error range for the strips, im not sure you could get much closer. The check/add salt light has been on ever since i opened the pool, really, but as long as the red light indicating low salt doesnt come on, (the unit shut down if that happens) i think it's ok. I could add more salt and get the green "salt ok" light on, or field calibrate it back to green, but i think its ok the way it is. i run it 15-20% and keep ~5-6 ppm FC. The "on time" or percentage the generator is set on is really not dependent on the salt concentration as long as the salt is at or above the level for generator operation.

As for the strips, i never have gotten the color change on the yellow band to change like the directions say. The salt strips seem to be pretty close to the local pool store's meter, though. For whats the stores meter is worth.

 

[bluenoise]

I don't generally trust the SWG's reading as the tech at Goldline once told me that it can often be off by about 400 ppm or so. However, my issue was that it was reading below the unit's minimum so it was shutting down and not producing any chlorine.

Thank you all for the confirmation of the strips' accuracy. While they've always been stored and handled properly, I will use them up before getting so close to their expiration date.

 

[Brad S]

If it reads below the units minimum, there should be a way to calibrate it and tell the unit the salt is correct and make it come back on. The Pentair i have will do that. i'm sure the aquarite will too.

 

[bluenoise]

Yes, the Aquarite can do that. I was recalibrating every couple of days, but it was still drifting down below its minimum.

Ultimately, the issue was that my pool actually was low on salt, but the near-expired test strips were telling me the salt was nearly 1000 ppm higher than it actually was.

 

[Brad S]

Ah, gotcha. Ok, i get it now. The strips were giving you a bad reading. I'll have to look at the lot number on mine and compare. A few others here have reported potential problems with the aquacheck strips.

 

[Guest]

The aquaarite is not actually being calibrated, you are just resetting the instant salt level. After a few days it goes back to the average salt reading.

 

[waste]

Hi all, here's my take on this.

If the unit thinks the salt is too low, it will not generate Keep the unit happy and go by what it says, unless the true salinity is ~ 1000 ppm higher than what it says it is (when it get's to that point you have to have the unit checked and make sure that there isn't some other problem)

No one is going to notice that the salinity is 3500 ppm vs. 2800 ppm - what will be noticed is if the unit won't produce chlorine and the pool is unhealthy to swim in