How exact do you have to be with water tests?

[phalcon51]

I'm pretty finicky about doing my water tests; I use exactly the number of drops called for, hold the bottle vertically instead of at an angle and generally follow the instructions to a "T". I occasionally take a water sample to my local Leslie's just to see how well their results agree with mine. Of the three employees that work there on different days all three have a different way of doing the tests. The worst one typically overfills the sample vials, puts in 8 or 9 drops of reagent when it calls for five, shakes the sample to mix instead of inverting, etc. Just wondering how sensitive these tests are to following the instructions exactly vs. just getting it sorta close. What's your experience?

Gary

 

[JohnT]

Some can be pretty touchy. Not holding the bottles vertically can lead to variation in drop size, and missing the mark on the vial can change the concentration as well. Most measurements of any kind are the worst when you combine errors such as small drop size and an overfilled vial.

 

[JesseJames]

I gave up on the pool store tests. Around here the employees are mostly college kids who couldn't care less about my swimming pool. I decided it was a waste of time.

 

[Bama Rambler]

Accurate testing is one of the major tenants of this site. I, like you make sure I do the tests as accurately as possible. I figure there's enough inaccuracy in the tests themselves that I don't need to be adding any due to my sloppiness.

By the way, I've noticed the same thing at the local pool stores around here to. They just don't seem to get it.

 

[benavidescj]

I don't see the point in doing the test if not done correctly. If done incorrectly you will get a result and may even take action based on that result which in itself might be inaccurate. I too do it accurately because I want to know exactly what I have. I am anal though and love my pool.

 

[JasonLion]

With a little attention it is easy to do the tests the way they were designed to be done, which will keep your errors under 10% (for the most part). When you are more casual about things like filling the vial too high or adding the wrong number of drops it is easy for errors to mount to over 40%, and possibly much more, depending on what you actually did. At that point you risk having a wide range of problems and losing control over your chemistry.

Many of the methods we teach here depend on maintaining reasonable accuracy/precision in your test results. Some errors are unavoidable and some of the tests are less precise than others. We try to take those issues into account in our recommendations. But when you start adding other mistakes on top of the inherent challenges, things can easily go beyond acceptable limits and cause problems.