Pool Water Tests - Conflicting Results

[homerlex]

I opened my pool last week and went to get my pool water tested today. I did not believe the results so I went right home got 2 more samples and went to 2 other pool places to see what they thought.

My Pool - 23,000gal Gunite/Plaster

Here are the results:

Before I went I took my own tests: Total Chlor: 3 Free Chlor: 3 pH: 7.4 Alkalinity: 80

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1st place I went: Saturation index: -1.5 TDS: 670 CYA: 99 Total Chlor: 1.4 Free Chlor: 1.4 pH: 6.8 Demand Drops: 10 Tot. Alkalinity: 56 Adj. Alkalinity: 26 Hardness: 146

They took the test and said your alkalinity is 26 you need to add 50lb of alkalinity up. Since I had just tested my self I did not believe the results. Besides this being low the wanted me to bring it up to 125 minimum. This is strange to me too as I have always been told 80-120 for my plaster pool. I questioned them and they stuck to their guns. After I left I noticed on the sheet they had something called Adjusted Alkalinity which is much lower than Alkalinity - I don't know where this adjusted value comes from but it was too late to ask. They use a system called "alex" by Bioguard.

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2nd Place I went: Total Chlor: 3.0 Free Chlor: 3.0 pH: 7.2 Total Alkalinity: 80 Total Hardness: 250 CYA: 50

They said my water was perfect - don't do a thing. They agreed that the alk should be in the 80-120 range.

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3rd place I went: Total Chlor: 2.0 Free Chlor: 2.0 pH: 7.6 Total Alkalinity: 90 Total Hardness: 170 CYA: 40

My own results seem to be more in line with the last two places. How could there be such a difference in opinion on pH, Alkalinity, CYA, and hardness?

Does the first place not know what they are doing or do they know something that the other do not know? I'm leaning tword the former.

Let me know what you think.

Regards

[Richard J Kinch]

Accurate and reliable testing is very expensive. It simply isn't available with methods like your home kit or the in-store testing. We may naively want to believe it works, but the cold truth is that it can't be trusted.

Most likely: (1) The first place is dangerously incompetent. (2) The others are just using colorimetric tests like you do at home, and these are necessarily very crude to start with, and often spoiled. Given the unknown condition of the reagents and the vagaries of reading subtle color changes in unknown light by uncritical persons, the figures agree within the expected error. This error is so large as to make the figures useless for anything but very crude prescriptions.

The water testing is just a gimmick to get you into the store and to sell you stuff. Your results how unreliable and inaccurate it can be, to the point of being utterly untrustworthy.

You have to do your own testing and learn to do it reliably. I like the big Pool Time test kits; they come (or used to) with coupons for several years of free annual refills via mail to keep the reagents fresh and accurate.

If you want to do testing right, see

and .

[Peabody]

I believe Adjusted Alkalinity refers to the idea that the cyanuric acid stabilizer in the water tests as alkalinity, but doesn't behave that way with respect to scaling or corrosion. They make an adjustment to remove the "false" part of the alkalinity.

This is a controversial interpretation, and in my experience since 1979, it just doesn't work in practice. The alkalinity test in my Taylor kit produces results which seem to work fine without making any adjustment. In other words, I keep the unadjusted TA within the 80-100 range, and over the years have had no scaling or corrosion. Also, pH tends to be stable in that range.

If I add the large amounts of sodium bicarbonate which would be called for by the adjusted number, it just makes the pH spike, and I end up having to add acid every day to bring it back down. Then when the ph has stabilized, I measure TA and find the unadjusted value to be 80-100. So in my experience, the whole exercise just encourages sales of bicarb, then acid, only to leave you right where you started.

If Alkalinity Up is really bicarb, as I suspect, then their recommended addition of 50 lbs is just silly. That would be

40 lbs in my 18.6K gallon pool, which is 10 big boxes of Arm & Hammer baking soda. If you really needed that, I think you would already be experiencing severe corrosion problems.

The other reading from store #1 that seems out of line is the CYA measurement. Even with Richard's warning about the accuracy of these tests, I don't see how they could get a CYA reading that is essentially double what the other stores get.

If I were in your shoes, I would not let store #1 measure my water in the future. It appears that all of their errors (if that's what they are) tend to produce larger sales of chemicals to you. Of course, that could be incompetence. Sure it could.

[Richard J Kinch]

The common CYA test is based on a precipitation reaction which is very difficult to read, and rapidly loses precision in the upper ranges.

[mark_digital]

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-------------------------------- I too have been down that full circle . But I'd like to add a different slant to this problem of inconsistant values from one dealer's test to another. Last night I shaved and splashed cologne on. A few minutes later I submerged my water bottle for the pool chemical test. The pH reading was way off from the day before. What was happening was the blue cap that covers the kit so it can be shaken was being contamenated when I touched it. It's happened before so it wasn't difficult to figure out. Cigarette fingers will contamenate the water too. So with this in mind, water for testing could be tainted by the pool owner or by the dealer's help, like in the case of smokers.

I suppose if your water gets tested by someone just coming off from a smoke break it could very well be quite different than your own test (unless you smoke too :)

mark_

[mark_digital]

Along the same lines, if the person doesn't wash their hands after a toilet break your TDS could be artificially high. Just kidding. mark_

[Oliver Costich]

I have found that the "free" water checking at most pool stores is completely unreliable. For example, yesterday I took a sample in and got a chlorine of 5.0 which they said was only as far as their scale goes so it was probably more. I used test strips and a chem test kit to check it myself and gor 2.0 on each. Another example: I can take samples in daily and the hardness result comes out somewhere between

250 and 400. The 250 and 400 were on consecutive days. The next day they got 320.

These places think (and do) hire just anyone can test. Evidently they are wrong. Get the right chemical tests kit and do it yourself. Nothing is really "free".

[Richard J Kinch]

It's not just the kid behind the counter. The tests themselves are inherently unreliable and imprecise, even if you do it yourself.

[Rein]

so, you're claiming test-strips are better ? Don't think so. Get a taylor kit, they work well enough. Never had a problem.

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[Lex]

Which Taylor kit do you use? There are a number of differnet kits

[Rein]

It's a basic taylor kit sold by leslie's It only checks chlorine and ph but does so well. I used to have a cheaper kit (brand-x) which works almost the same. Used it for a few years but was never happy with the colors on the glass that you have to match with your water. The taylor is better for sure. For all other tests (like stabilizer) I have an older kit which I really never use. I take a sample to leslie's and have them do it (maybe 3 times a year). I see them do it and know they do it correct. I have never had ANY problems. I only add chlorine and acid, that's it. Never had algae, never had cloudy water. Never had green hair or other discoloring/smelly water. This is in Arizona and in July the water goes up into the 90's , and if there's a place that algae likes to grow in it's in 90+ degree water. Never had algae. Best way to maintain a pool is test it regularly for ph and chlorine and keep those two up. I test it about once a week, sometimes I skip a week (depends also on usage). In winter I check less since there's not much chance of algae and the chlorine stays in the water much longer.

good luck. Pool maintenance is easy.

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[jlangdon]

Hi,

I just wanted to offer my thoughts for what ever they may be worth. work at a pool store owned by my grandparents. This is there 25th yea in business and I have been there 13 years of it. We are from a smal area they call us a maw & paw store but the business is growing b leaps and bounds we have in excess of 1000 customers which might not b lot to some but around here it is a lot! Anyways I agree with the on who says a lot of pool stores hire just anybody to work inside, som do, the other pool store around here hires a lot of high school girl to run the water test, they run it on the computer read the result (not knowing what they mean) and sell you the chemical to fix th problem. There is 2 problems with that: 1) the person hasn't a clu what they are telling you & 2) the computer program is meant to sel the chemicals. For insist in you alk is 50 & the safe ranges o chlorine is for it to be 80 to 120, the computer is going to sell yo the max to get you to the 120 mark, that way when you come in next the will have to sell you something to lower the alk. that where th experience counts, our pool store has 4 main girls in the office and w have all been there at least the 13 years all the way up to the 2 years, we do have a couple other girls who answer the phone, show th pools, and can even run the pool test but then passes it on to one o us who has been there longer. We also have the computer programing bu we don't use the computer part (the parts that tell us what you shoul do) we run the water in on our labs UDV in that means anything t anybody & we know what to tell them with out the computer, we woul sell you the least amount to get you into the safe range. I know som of you doubt what I am saying but it is true, if you are not happy wit us you may not come back and you definetly won't tell anybody about us the the other pool store went bankrupt last year I think we are doing good job. But anyways if you were to come into our store for say & w came up with that reading you got in pool store #1, & if you told u that isn't what you got, we would have reran the test (the vials can b wrong) we would probably have check it with strips too and if we wer still off that much we would told you to do nothing bring in anothe sample in a few days & if possible bring your tester so we could se what was going on. I personally think that is nuts telling you to ad

50lb of increaser, I don't ever recall selling that much to anybod even with ones with 0 alk. I know we have sold 24 lb before but the i the largest amount I ever remember & that isn't to often. We do offe the free water test for anybody that buys their chemicals thru us, eac test runs us $10 to run and they can come in once a day, once a week o as often as they need to be comfortable with their pool and I am no saying they have to buy each time they come just over all buy thei chemicals from us because there are plenty of times people don't nee anything or have it at home. We just usually say to bring in you water once a month to get it tested so the things that can't be teste at home are checked, I know some test check the alk but some don't & i the alk is truely low & not corrected in can pull plastcides out of you liner & cause pin holes. I am truely sorry for those of you who don' offer a good honest pool store. We strive hard to be one. Good luc to all and sorry I rambled on & on! ~Jessica [e-mail]

-- jlangdo

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[gfretwell]

That seems to be the main thrust of all in store pool testing. I never use as much chemical as they tell me on the first dose. It is a lot better to work up to the right level than to slam in a bunch and overshoot. Most of the time they tell me my water is OK but they still have some magic potion I could use to make it "better". Anyone with a pool should get the 5 bottle kit (as a minimum) and learn how to use it. Those strips are pretty much useless.

[Sacramento Dave]

I recently bought a house with an in ground pool, I did know a pool had a filter, pumps, water and ate some amount of Chlorine other than that I was lost. But after about 6 months I have got it under control. Most people said get a pool service. In my area the rate is about $60 to $75 a month and that's just to check the water and put chemicals in. One thing I found right off is find a decent pool supply that actually try's to help you. I went to the big pool chain store ( I don't want to say there name but there initials are L E S L I E 'S) they always had something I had to have. I do test my own water and also have the pool store test it. There some things you realy can't test yourself.

[Pop]

No, the stips are not useless: They are a good, cheap interim check for your pool, though NOT a replacement for a good testing kit. Eventually you catch onto the nuances, and the strips save money if you're testing correctly and on the right schedule. ANYONE that's surprised by anyhting in or about his pool isn't paying close enough attention to it.

Cheers,