Test Kit Duel

[mattman44]

Hello everyone. I've been stalking this site for a little while and you guys put out some really good information.

I manage a seasonal beach club business in New Jersey with two pools (100,000 and 5,000 gallons respectively) that see pretty heavy use. Unfortunately I also have about 14-16 high school and college aged guards doing hourly FC TC pH tests for me. Earlier in the summer after double checking some questionable readings with our standard Taylor kit I wanted to try and take the subjectivity out of the results (obviously I, as our CPO, am modifying chemical distribution based on those readings). What looks like a FC 2 to one person is apparently a 4-5 to another. Anyway we invested in a Lamotte Colorq Pro 7-Plus. After a brief show and tell with the guards for proper operation we were off and running. Things seemed rather normal at first. Then a week later there would be multiple times we would get a crazy difference in both FC and PH in an hour's time (and I'm talking like 4.6 FC to 1.4 or just this morning we had a PH from 7.6 to a 7.0 in the big pool with little use). I compared a Lamotte reading with a Taylor reading (one right after the other) this morning and the results were -

Lamotte - FC 1.44 <did this twice and readings were similar>
pH 7.0

Taylor - FC 5
pH 7.8

All of the reagents are new and the batteries are brand new in the Lamotte kit. Does anyone have this kit or know of any problems with it? As of now it's shelved in favor of the old drops and color chart until I can figure out what's going on. It makes sense that the Lamotte kit is off because we use an automatic sodium hypochrlorite chrlorinator in the big pool and the pH readings are never such that I've had to add much of any muriatic acid this summer (which is unusual). Of course, then the taylor kit indicates pH is running high, which makes sense. Any help, insight or advice would greatly be appreciated.

Thanks!

 

[PoolGuyNJ]

Are you using an ORP sensor for the feeder? Has your hypochlorite usage varied much? Are you using more than usual?

I am willing to bet the Lamotte is out of calibration. A TF-100 or Taylor K2006 kit will give much more accurate readings when used properly. Since they are using DPD-FAS for chlorine testing, the local board of health will be happy.

If you're in Monmouth or Ocean County, I can show you my TF-100. I think you'll like what you see.

Scott

 

[anonapersona]

When I had lots of aquariums and hung out in an aquarium forum, several people had the Lamotte pH meters and they said it had to be recalibrated FREQUENTLY. The consensus seemed to be that with all the effort at calibration, that it lost a lot of the convenience that they had invested in.

 

[JasonLion]

The ColorQ recalibrates during each use.

I've seen them be off, but not like that. The main thing to watch out for is the test vials getting dirty. If the outside of one of the vials gets dirt/grease on it your readings can be way off when you are using that vial.

 

[mattman44]

Thanks everyone. Calibration makes sense it just surprises me it needs to happen so soon I guess. It's only a little over a month old.

Pool Guy - Yeah I'm in Sea Bright, central Monmouth County. We have been using more Sodium Hypochlorite this year for sure (as have other clubs along our strip in talking to them). I think we mainly chalked that up to the rather sunny/hot summer. Cyanuric levels have been ok (although we've added some extra of that this summer too). We do use an ORP sensor in our systems for both pools that were both recently replaced a few weeks ago due to age. The system works pretty well, we've mainly been very happy with it. The only issues we had were some off the wall pH readings at the box which is why we had the sensors replaced. Even then they can vary up to a few tenths with the drops test. The chlorinator machines have a recalibration option on them though.

Jason, I tried to tell my employees to wipe off the vial before a test knowing the sunscreen/sweat and other fun oils their hands are exposed to. These we have now are plastic and don't smudge too bad. I'm used to cleaning them off in that type of system anyway because in college at the pool I worked at we had glass vials. So if you didn't wipe them down you were almost guarateed horrible readings.

I'm just bummed we spent a few hundred bucks on a product that was supposed to solve a common problem and ended up creating more hassle and costing the club in extra chemicals to boot. Since there are only a few weeks left of the season I think we'll probably just ride it out. Then we'll go to either the TF-100 or Taylor K2006 kit for next year. Thanks everyone.

 

[tim_pool_newbie]

You haven't been letting Snooki in the pool, have you? That would certainly explain it!! (ah come on....it had to be said!! LOL)

 

[loop_pea]

One possible reason for a big difference in FC readings is that the vials aren't clean on the inside. If they contain even a tiny bit of DPD3 it releases the CC and you end up measuring TC rather than free. Then you appear to have a wild swing in FC level from one test to the next, when in fact one reading was artifically high. (You didn't say what your CC level was but I doubt that it's zero in a heavily used pool). Just a thought.

We use photometer testing (different make of instrument though), and I keep discovering new ways that it's possible to reduce the accuracy of the test. The most repeatable test seems to be CYA, while the most iffy test is pH. We're sending our photometer back to the manufacturer after just a couple months since the last calibration because we're getting wacky results, even though we've tightened up or test procedure (in our case calibration is guaranteed for six months).