how reliable is store water testing?

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MikeInMo said:
WaterBear,

What is the proper development time on those tests? The system described sounds like what one of my pool stores uses. Little square vials with foil coverings that the tester punches thru with the ?pipette? [learn a new word every day]. The vials are probably somewhere bt an inch or two in height and the color of foil varies, assuming with the different test. I tink what my store does is just fill all the vials at once and then run them thru the meter one by one. I assume that the vials first filled are the first anlayzed but it doesn't appear that there is any set wait time.
Is that what you'd expect?


I just recently purchased the LaMotte ColorQ and am enjoying the geek factor but the directions never mentioned any wait times except for the CYA test. Based on your experience with other LaMotte products what special procedures would you recommend (i.e. wait time after adding drops before analyzing or wait time bt adding reagent 1 and reagent 2, etc.)

Thanks,
Mike
Click to expand...
The vials are arranged in this order left to right on the rack: FC, TC, pH, CH, TA, CYA, Copper, Iron, (and if they have the upgrade then Nitrate and Borates).
The blank is put in the colorimeter with pool water to calibrate it so any cloudiness or color in the water will be compensated for and the machine turned on. Then the vials are filled from right to left so the FC is filled last. EAch vial is inverted 3 times before reading and NOT shaken. If there are air bubbles or powder stuck to the vial it should be tapped on the counter and then inverted again before reading. The FC is read immediately(within 30 seconds of filling) for accurate results then the other vials are read in order. The TC is read once the readout on the unit stabilizes and then the other vials are read. This procedure allows proper development time for the different tests. FC is immediate, TC and pH need to be read after 1 minute up to 5 minutes, CH and TA read after 2 minutes and up to 5 minutes, the others read after 3 minutes and up to 5 minutes. If the machine is calibrated with the blank before the vials are filled. the vials filled from right to left, and read from left to right after inverting them three times then the timing is usually correct. BE aware that the Datamate software that is used with the unit, while one of the better software packages out there, has a tendency to overdose on TA adjustments because it is assuming the pool is using trichlor, which is acidic. Also if the pool has a SWG it will say the CYA is ok even if it is too low for a SWG because it doses to about 40 ppm. If the volume of the pool that is entered is not accurate then the dosing recommendations will not be either.

There are some known interferences with the tests. If the chlorine levels are high then TA will read low and pH can read high. I disregard any TA readings when the chlorine is above about 8 ppm. Their pH reagent generally is as good as the Taylor and seems to be accurate up to 10 ppm FC or TC. Also, if there are metals present, particularly copper, then the CH will read low. These interferences are not unique to the Lamotte chemistries but affect all test kits to one degree or another.
 
thanks everyone...for the stories about your local stores and testing...I've got a handle on home testing now (or at least I'm deluding myself into thinking that..lol) so I'm staying far away from that store for any info from now on. I did take a sample in today, just for ha-ha's, since I needed a solar reel there anyway. they were wrong yet again...told me my cya and ph were low--that I needed x # of lbs of stabilizer and ph increase HAHAHAA. my cya is at 30 and ph is 7.2, but not that off to require lbs of anything. I now believe that they read tests according to what they overorder each week :shock:
 
I will add to this.

I went to the closest pool store to me today. It is 35 miles away in another town.

The pool girl took my sample water and put some of it in some little apparently one time use vials.

She also did some tests with strips. :roll: I knew then that I would take her advice with a grain of salt, but decided to see what she came up with.

I have a vinyl lined pool. She said that my calcium was way too low and tried to tell me that I needed to add 20 lbs of calcium to my water. I told her that it was a vinyl pool and that calcium was not necessary for vinyl or fiberglass lined pools. She said that my water would get foamy if my calcium was too low.

The main reason that I wanted the test was for my CYA, which I have tested once, and it read 0. She showed it to be at 10 ppm. So, I bought some CYA from her. There was an unopened container of it in the shed when we bought the house, but obviously it is no good. I put 3 lbs of it in a sock a week ago, and it has been gone for 3 or 4 days, but it didn't help any.

She complimented me on the clarity of my water, my pH, and my free chlorine (0.4) and said that I was doing very well for a first time pool owner. She knew that I had a green slimy mess a few weeks ago.

She asked me what kind of chlorine source that I was using, and I told her that I was using pucks in the skimmer in the daytime, and using liquid at night. She said that liquid chlorine is against the law in Arkansas, and wondered what strength I was using and where I got it.

I told her that it was 6% and that I got it at Walmart for $2.24 per 174 oz bottle.

She figured out that I was using bleach. :lol: She warned me that I was going to fade my liner and that bleach would ruin my equipment.

I took that as my signal to leave her store. :roll:
 
I have seen 5 1/4% liquid shock at both WalMart and Target, so your story isn't so implausible. Even in areas where 10% and 12% are not allowed, they can still sell 5 1/4% and 6%.

Low calcium causing foam and bleach ruining your equipment are of course silly. Any kind of chlorine can fade a liner, so there is a tiny grain of truth to that one but the way they say it is misleading.
 
Actually, low calcium CAN cause foaming! Low calcium means soft water, high calcium means hard water. Soft water is does have more of a tendency to foam when soap like organics are in it than hard water and many of the organics that collect in the water do have this property. Anyone with a water softener will know what I am talking about. However, a calcium hardness slightly above 100 ppm usually enough to keep this from happening. This effect is more evident in a hot tub, with it's air jets and bubblers, then in a pool but if there are any water features present that 'churn' the water such as jets or waterfalls it can become noticable.
 
amieelynne said:
thanks everyone...for the stories about your local stores and testing...I've got a handle on home testing now (or at least I'm deluding myself into thinking that..lol) so I'm staying far away from that store for any info from now on. I did take a sample in today, just for ha-ha's, since I needed a solar reel there anyway. they were wrong yet again...told me my cya and ph were low--that I needed x # of lbs of stabilizer and ph increase HAHAHAA. my cya is at 30 and ph is 7.2, but not that off to require lbs of anything. I now believe that they read tests according to what they overorder each week :shock:
Click to expand...

Actually, many pool stores will try to get the CYA to about 40 ppm since it is in the middle of the recommended range. 30 just usually is a bit low if the sun receives any substantial amount of sunlight. Also, while a pH of 7.2 is within range it is on the low end. I personally tell people to keep the pH at 7.6 since it will result in better pH stability in most pools.
So you are right in saying that your numbers are fine but the store was also right in telling you that you needed to raise both of them.
 
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