Poolstore water testing. Who should I trust?

[peterl1365]

First, let it be known that I have color vision impairment, so I don't trust myself to do my own testing.

That said, I have been using two pool stores to do my testing. One of them is Leslie's, and the other is an independent called Cal-West that primarily sells spas. I have also been using an Aquachek TruTest digital tester to do my day-to-day FC and pH measurements.

The problem is that the two pool stores have been getting different results for certain key tests.

Leslies: CYA 25ppm
TA 130 ppm

Calwest: CYA 40 ppm
TA 60 ppm

Leslie's uses their standard reagent testing, while Cal-West uses an automated test strip reader made by Hach. In each case, I've had the water tested within 20 minutes of each other.

I like the idea of taking the (possibly poorly-trained) human tester out of the equation, but I'm concerned about the accuracy of the automated tester.

Which set of results should I trust? Any opinions?


BTW:

~13,000 gallon pool (no spa)
520 SF cartridge filter
white quartz plaster
Pentair IC40 SWG

 

[JohnT]

Even with your vision, I'd still consider getting a liquid reagent kit and doing it yourself, with a little help if needed.

The CYA test is subject to quite a bit of interpretation, but luckily for you doesn't require color.

TA testing with liquid reagents is pretty straightforward and not subject to interpretation. You just count drops and look for a color change from green to red. In your case, that's not as simple as it sounds to many of us, but if you can find someone who will do the dropwise test you should get an accurate reading. Normally you don't need the TA test done very often, so even though you may not be able to do it, it wouldn't be too big of an imposition to get somebody else to tell you when the color changes.

 

[The Mermaid Queen]

Take it to WaterBear's store!!

Seriously, you don't have to see the color the same as folks with regular vision, you just need to be able to compare the two colors, and in my experience with DH, who is also color impaired, he is the BEST at matching colors.

So get a good kit, or even get a cheapy OTO/pH test, and see how you do with that. Have a family member or friend double check your results the first couple of times to be sure.

Personally, I would trust DH's color-impaired results before I would trust most pool stores

 

[Guest]

Hach is also the company that owns AquaCheK. IMHO, strip readers just are not that accurate. A colorimeter that uses liquid reagents or UDV's (unit dose vials) of dry reagents is going to give the most accurate results but they can cost quite a bit of money! (into the thousands!) although Hach does have one model will test FC, TC and pH using liquid reagents for under $400 and LaMotte makes a range of pocket testers and handheld colorimeters that can test a variety of water parameters. IF you keep them calibrated they work well (But from my experience with them they need frequent calibration). Their pocket colorimeters come in 2 models, One tests FC, TC, pH and CYA and the other tests FC, TC, pH and ALK.
Now, it is said that even colorblind people can read the FAS-DPD titration test for chlorine (changes from vivid pink to colorless) and if you can differentiate between green and red the TA test is not problem. It is a titration test with a definite color change from green to red. CYA is a turbidity test that does not rely on color recognition. pH drop tests depend on being able to differentiate between yellow, orange, red, and purple shades (here is a test that a meter might be useful for BUT you NEED to keep it calibrated with standard solutions!) , and the calcium hardness test is a titration test with a color change from pink to blue, Once again even colorblind people are supposed to be able to differentiate the endpoint of this test.

EDIT: Taylor has a demo slideshow on their website which shows the color changes in the FAS-DPD test for chlorine. You might want to view it to see if you can tell the endpoint of the test.
http://www.taylortechnologies.com/slide_shows/FASDPD/index.html

And a stillshot
http://www.taylortechnologies.com/ChemistryTopicsCM.ASP?ContentID=11

 

[medvampire]

peterl1365
I am color blind my self and have found that a white backgrund behind my test vial helps to read the liquid reagent testing. The white gives me a way of seeing changes in contrast and hue of the few colors I can see. I second watebears FAS-DPD method for chlorene testing. I have found by adding acid or base demand drops to my pH test allows me to zero in on the pH. The CYA test is no problem for me to read. I had my wife read with me the first few times to give me end points on CH and ALK.
Later
Steve

 

[DavidD]

peterl1365

I would also recommend finding a way to do your own testing as I've also seen the variances the pool stores give. My own experience is that they are manned by teenagers or employees that really believe what they are saying, but lack the knowledge to actually know exactly what they are saying. Unfortunately, we cant all have an Evan (Waterbear) at our local Pool Store . Trust no-one!

Dave

 

[duraleigh]

I'm gonna' "glom" on to Evan's post and encourage you not to trust test strips and/or pool store testing. From years on PF, there was constant discussion (and examples) of innacurate testing from strips and, generally, from pool stores. The results of a test are no better than the tester and, it seems, pool store testers, whether human or computer, can't provide results as accurate as you can provide for yourself. Work around the color-blind issue....it's worth it.

 

[peterl1365]

Thanks for all the advice. For the time being, my TruTest strip reader "gets me in the ballpark" with regard to FC. The poolstore testing has pretty much confirmed the Trutest in this regard (within about 1.0 ppm). I think this is accurate enough. As for pH, the TruTest seems to read consistently about 0.2 to 0.3 pH high. I have a digital pH meter that I borrow from work occasionally, and it is supposed to be accurate to within .01 pH. It's only been calibrated with pH 4.0 buffer, so I suppose I should get some pH 7.0 buffer to really calibrate it.

As for CYA, I don't see any need to test for it on a regular basis. Once it's in the range of what I want, I'll probably ignore it for several months. I just want to build it up without overshooting my target of 50ppm (this is a brand new pool). If it truly is a turbidity test, then I'm leaning towards trusting the results from Leslie's rather than the strip reader.

TA is the same thing. There is such a broad range of "acceptable" values that I just want it somewhere near 100 ppm.

That all said, I'm going to look into the wonderful advice all of you offered. Thanks again.

 

[Guest]

TA is the same thing. There is such a broad range of "acceptable" values that I just want it somewhere near 100 ppm.

Actually that's not quite true. The range for TA is quite broad but where you want to put it really depends a lot on the type of chlorine you are using. If you are using one of the acidic stabilized chlorines you want it at the higher end of the range because dichlor and trichlor will eat up your TA and cause you pH to fall. If you are using a nontabilzied chlorine or a SWG you will get much better pH stability and less acid use if you put your TA at the low end of the scale or even lower than is commonly recommened!

 

[giulietta1]

Nor is there universal agreement on the "right" TA level. The local pool store mainly sells a particular brand and uses their testing analysis software. It generates a printout with the tested levels and recommended levels, recommending 125-150 for TA!

My pool's TA has been running around 110 and I have been having to add acid at least once a week. Doesn't sound like a low TA to me!!

 

[Guest]

While it is generally accepted that you can run a higher TA in vinyl and fiberglass pools since their surfaces are non reactive, once again I say that HOW high you run yo TA depends on the type of chlorine you are using. Acidic chlorine sources (trichlor and diclor) cause your pH to constantly drop and deplete

the TA. By running the TA around 100 or above your pool will have a tendancy to keep rising in pH so it will counteract the effects of the acidic chlorine source (same applies if you use MPS to shock, which is also acidic or if you use tablet bromine).
If you are using liquid chlorine or one of the unstablized dry chlorines (lithium hypochlorite or cal hypo) or you have a SWG then you will find much better pH stability and less acid use to maintain pH if you run your TA below 90 ppm and possibly as low as 60 ppm before stabililzer correction.

Be aware that most of the software for pools is 'dumb' and does not take into account the type of chlorine source nor the surface of the pool. Also, many times the software is set up to sell chemicals. The printouts can provide valuable information if you know what you are reading so they do have some value.

I suspect that your pool store is a bioguard store that uses the ALEX system with test strips and a strip reader. This is one of the worst, IMHO. LaMotte has a system with a colorimeter for reading what is essentially a reagent test. They used vials of dry reagents (Unit Dose Vials) and produce accurate results. The Datemate software that goes with it is a bit brain dead but not that bad. It has a lot of optons on how it can be set up but be aware that the store is the one who sets up what is on the printout so if their goal is to sell you chemicals that is what the printout will try and do.

IMHO, I would be suspect of any testing method that is produced by a product company! Taylor, LaMotte, Hach (AquaChek) are not in the product market. They only sell testing kits and equipment so they don't have a vested interest in trying to sell product.

 

[giulietta1]

It's an Omni dealer. She's not too pushy about selling the products, tho.

My pool's TA was about 90 last time I tested it. The pH has been pretty close to perfect, around 7.4-7.5, and the water looks beautiful. Once the water temp is above 80 I'm sure we'll be in it a LOT!

 

[Guest]

Omni is one of the Bioguard lines. Your pool store is most likely testing with the ALEX system (strips, a reader, and a computer print out designed to sell chemicals!) My advice is to run and don't walk to a different pool store! Find one that tests with Taylor or LaMotte reagents.

 

[CarlD]

Better still, do your own testing.

Again, only the pH test requires color tint matching. FC, CC, T/A, CH all have a VERY dramatic change which even colorblind folks should see (I don't know if those with total colorblind-ness--monochrome vision can see it, but they might). I'd get someone to help on the pH test.

CYA doesn't require color perception at all--it's strictly a monochrome B&W test.

I've never had a pool store test my water. I'd only suggest it if someone needs to test RIGHT NOW and doesn't have a proper test kit.

 

[TheOne]

Just to add about questionable pool store testing...

I thought I needed a different test kit to test FC over 5ppm. So I went to Leslies and another local pool store to ask if they have a kit that tests for chlorine over 5ppm. They both said no dont have them and they were sure they didnt exist.

I went home and actually looked at my Taylor Kit and it says right there on the box how to test for FC over 5ppm.

* If color is off-scale: Repeat test using 4.5 mL sample diluted to 9 mL mark with tap water. Multiply reading by 2 to obtain approximate sanitizer level. If color is still off-scale: Repeat test using 1.8 mL sample diluted to 9 mL mark with tap water. Multiply reading by 5 to obtain approximate sanitizer level.

What concerns me is why a pool store that sells taylor kits did/does not know that. I have about a weeks worth of pool chemistry knowledge and figured it out.

 

[giulietta1]

There isn't another pool store in town. I do my own testing and I buy most of my pool stuff elsewhere, online if it's pool-specific or at the grocery store or WalMart if it's bleach or something like that.

Jules

 

[CarlD]

What concerns me is why a pool store that sells taylor kits did/does not know that. I have about a weeks worth of pool chemistry knowledge and figured it out.

Concerned? It's typical. I actually had one Leslie's employee GIVE me the jar of FAS-DPD powder because he had no idea what it was or how to price it! The other day a Leslie's emp explained to me how Liquid Chlorine is bad because it builds up the Total Dissolved Solids and that TDSs are a MAJOR problem. I "Uh-Huh" 'd him since he clearly didn't know a cave bat from a baseball bat!

The kicker is that Lesllie's is one of the BETTER chains. Staff in pool stores rarely know anything, and most of what they DO know is usually wrong.

If I worked in a pool store I'd be fired because I'd be telling people not to buy the BioGuard Total Alk Raiser at $12/ 4 lbs since you can buy 12 lbs at Costco for $3.50! (about 1/8 the price).

 

[medvampire]

Just to add about questionable pool store testing...


* If color is off-scale: Repeat test using 4.5 mL sample diluted to 9 mL mark with tap water. Multiply reading by 2 to obtain approximate sanitizer level. If color is still off-scale: Repeat test using 1.8 mL sample diluted to 9 mL mark with tap water. Multiply reading by 5 to obtain approximate sanitizer level.

Be cautious when doing dilutions. You extend the test range but will loose in resouliton. Also dont use tap water if you have a civic water supply due to the chlorene in the city water. I would recomend getting a jug of distilled water for doing your dilutions.
Steve

 

[CarlD]

Just to add about questionable pool store testing...


* If color is off-scale: Repeat test using 4.5 mL sample diluted to 9 mL mark with tap water. Multiply reading by 2 to obtain approximate sanitizer level. If color is still off-scale: Repeat test using 1.8 mL sample diluted to 9 mL mark with tap water. Multiply reading by 5 to obtain approximate sanitizer level.

Be cautious when doing dilutions. You extend the test range but will loose in resouliton. Also dont use tap water if you have a civic water supply due to the chlorene in the city water. I would recomend getting a jug of distilled water for doing your dilutions.
Steve

I agree. Steam distilled water is available at any supermarket for a buck or two.

 

[peterl1365]

Just to add about questionable pool store testing...

I thought I needed a different test kit to test FC over 5ppm. So I went to Leslies and another local pool store to ask if they have a kit that tests for chlorine over 5ppm. They both said no dont have them and they were sure they didnt exist.

The funny thing is that Leslie's actually has a kit (with the Leslie's brand name) that is designed to test up to 20 ppm. I'm pretty sure that it's just the Taylor FAS/DPD test, but the label clearly stated that it was for high-range testing. I presume that this is part of the standard inventory in every Leslie's store.