Oxidation Reduction Potential -- HELP

[hamop78]

[Full original thread moved to the China Shop -- PoolDoc]

I've been watching this and other forums for a while and I finally found the need to register and "ask the experts"

Here's the deal --- I got an instrument to read pH, which had ORP as an additional capability. After 3 different instruments all Extech PH220-C (2 bad ones) I have one that appears to read something in mV.

My pool is crystal clear, here's the specs as of tonight.
Temp 85F
pH 7.54 (calibrated electronic & titration)
FC 7.0 ppm (FAS-DPD)
TC 7.0 ppm (FAS-DPD)
CC 0 ppm (FAS-DPD)
TA 90 ppm (by titration)
CH 230 ppm (by titration)
Phosphates <100 ppm (titration)
CYA 60 ppm (25ml sample using 0013 reagent)

I am using a modified BBB (using up a bucket of Cal Hypo substituting 12 oz Cal hypo per recommended gallon of bleach)
I haven't had any pucks in for well over a month.
I used a small amount (2lb) of Potassium Monopersulfate a couple of weeks ago (more stock to use up)

Here comes the question ----
My ORP is reading negative 19mV

With my pool being nearly perfect (IMHO) how can that be??? I figured I should be in the 650 - 750 mV area. I have not used any reducing agents, and from everything I have read (many internet pages)--- my treatments should not be affecting the ability to display a proper mV reading.

Any help -- Ben, ChemGeek, Waterbear, ANYBODY!!!!!

[waterbear]

First,
Welcome to, IMHO, the BEST pool board on the net! I saw your post on another board about your ORP meter and I have to agree with the answer given there. Your meter or electrode is probably defective. This is one of the main reasons that I do not like electronic testers....they tend to be delicate and the probes can be expen$ive to replace! Also, pool chemistry ain't rocket science! Your numbers look great, the pool is clear! I have a question....why aren't you in it swimming and enjoying it instead of stressing over a strange reading from an ORP meter that is obviously broken! The fact that you are on your third meter with 2 known defectives says something!
My advice is ditch the meter and enjoy your pool!

[hamop78]

Thanks Evan,
I was doing both just this evening ---- Swimming back and forth looking at the @#%* meter --- the mfg said to let the probe in the pool for a while (30 minutes) to see if it would change. Since it shuts off automatically after 15 min of inactivity -- every third lap I'd punch the mode button. After an hour and a half of back and forth and punching the button (it never changed), I said the &^%@ with it, and swam until dark.

I have a Hanna probe coming tomorrow. We'll see how that reacts.

As I said on the other forum I'm a Techno-Geek. Your right --- it's not rocket science ---- but I believe technology can help us even when the masses think we don't need it. After all if the big guys use the technology to treat the community pool or treat our drinking water supply. Why shouldn't we, especially when we can get the instrumentation for a hundred bucks!!

I'll let you know how the Hanna reacts --- but I really think this meter is reading correctly (I compared this one with a thousand dollar meter at our water treatment plant where I work and a standardized solution --- It was dead on!!), which begs the original question --- How can it be that my pool water is -19??

[hamop78]

OK ---- Evan ---- Time for me to eat a big slice of humble pie .

More investigation at a community pool led me to question the tests of yesterday. Seems that the guy from work told me that he discovered a problem with his equipment and that the "Standard" may have been contaminated. So Much for "dead on". OH WELL!!

Anyway ---The meter is definitely toast--



[post trimmed by PoolDoc]



Edit: I did a 2 point pH calibration of the Hanna meter with NEW standardized solutions --- 7.00 & 4.01 --- Hanna now recommends frequent calibration for accuracy

[hamop78]

Well 4 down --- ??? to go. Yesterday the Hanna showed an ORP of 550 --- I'm getting closer --- FC was 7.5. Other results about the same. This morning FC 6.5 ORP 534. Went to give better half instructions on how to get the readings ----- DEAD!!! ----- Won't even turn on. Does anybody make something that works???? DISGUSTED!!!


[PoolDoc note: This is exactly the sort of problem I had with Hanna products years ago!]

[Jakebear]

[SNIP! PoolDoc]


Would love to get a running dialog about ORP started somewhere. Perhaps in China Shoppe. I am a believer in the science but lack experience. I will be upgrading my ORP Instrument because sample rate is tooooooo slooooooow! Takes an hour to stabilize if I move it to a different location.

( PoolDoc Note: This is typical of ORP electrodes. )


[SNIP! PoolDoc]

[PoolDoc]

I have a Hanna probe coming tomorrow. We'll see how that reacts.

As Waterbear noted, I don't care for Hanna products. I have a box full of old, useless portable ORP, pH and TDS meters made by Hanna! At the time I bought them, I was still listening to the siren call of "better pool water through high technology". Hanna's products then (15 years ago) worked when new, but were very poorly made, and broke or failed promptly! I don't *know* that they are still making their products the same way . . . but the cases are still the same! (I should note, in all fairness, that I had pretty good success for the price with their electrodes.)

As I said on the other forum I'm a Techno-Geek. Your right --- it's not rocket science ---- but I believe technology can help us even when the masses think we don't need it. After all if the big guys use the technology to treat the community pool or treat our drinking water supply. Why shouldn't we, especially when we can get the instrumentation for a hundred bucks!!

The reason to avoid meters in testing your pool is the same reason test strips should usually be avoided: they don't work well for the purpose!

Strips are inherently not very accurate.

Some meters are capable of giving extremely accurate readings, depending on construction and quality . . . but only if calibrated frequently and used properly. That "if" is a very big one.

In addition, only pH meters directly measure something of importance to pool owners. In spite of their complexity, they have a place in pool treatment, simply because thousands of pool owners have impaired color perception, making it difficult to use phenol red color-match tests reliably. One of my projects for this winter is to find a portable pH meter reliable enough to be built up in to a add-on replacement component for the pH test in my kit. However, it will NOT be recommended for everyone with an extra $110 or so to spend!

But, the other meters -- ORP and TDS -- measure something that's essentially useless to pool owners. Both measure something you DON'T need to know (redox potential OR aqueous conductivity) and then use it to guess at (infer) something you do need to know (chlorine level OR overall water condition).

Using a $2,000 Orion mV meter and ORP probe to measure your pool's chlorine is sort of like using a $500,000 X-ray machine to take family photos. It's certainly high tech, but it's still pretty useless for the purpose!

Using a $100 Hanna ORP meter to measure your pool's chlorine is more like using trying to use a TV-advertised "Ronco Miracle Slice & Dice Stamp and Serve Food Chopper" to fix fish for supper -- it not only doesn't work well for YOUR purpose, it doesn't work well for ANY purpose!

High technology doesn't help when it delivers results that aren't what's needed!

But the real secret here is that, apart from the LCD readouts, both ORP and TDS instruments are "old-tech", having been around for more than 50 years! What's more, they usually are often NOT used in water treatment, for the same reasons that they aren't useful in pool treatment: they simply don't measure what water treatment plant operators need to know. And, where they are used, the are monitored and calibrated frequently. The reason they have to be calibrated so often is that there's no consistent relationship between ORP and chlorine levels, or between conductivity and TDS, much less overall water quality.

Calibration just means that the machine's guesstimate is adjusted so that it's right. But, just guess what's used to calibrate the expensive high technology ORP based chlorine meters? Yep, it's the inexpensive DPD-FAS test used here for pool chlorine measurement!

The conclusion is simple: high technology pool measurement equipment is NOT a means to better management.

Rather, the gadgets (with the single exception of pH meters for those with impaired color perception) are the goal themselves. All of us Y-chromosone-types have an inbred, genetically driven, tendency to fixate on electronic gadgets and female chests. Jeri Ryan exploited this perfectly as Star Trek's Seven of Nine. No, I'm not saying that's all bad. I like my Y-chromosone, thank you very much. What's more, both my wife and I both enjoyed Star Trek - Next Generation, though she didn't find Jeri Ryan's character quite as fascinating as I did. But I am saying that gadget-envy does not lead to better pool management, and consequently, doesn't really belong in the general PoolForum areas.

I put it on my winter to-do list, and promise I'll try to add a gadget-lovers section to the forum by next year (2007). But, meanwhile, I'm moving most of this thread to the China Shop!

Best wishes,

Ben
"PoolDoc"

NOTE for MODS: I'm leaving thread unlocked for the moment, but if it veers back into 'gadget-tech', it should be locked. Until I can create a 'Gadget-tech' section, such threads belong in the China Shop.

[hamop78]

Ben,
Thanks for your input and moving the techno-speak to China Shop. As for me -- it's computer control on my solar system, GPS in the car, Ham Radio Cell phones & PDAs --- Automated Pool Control --- Maybe some day.

In the mean time I'll look forward to your Gadget Lovers section next year!!

As for this thread ---- I'll let my "FURBY" tell you ---- "Me Done".