Comparator vs drop test results

[OWSwimmer]

My chlorine comparator test results are different from my drop test results. Is this normal or am I doing something wrong? Chlorine comparator routinely shows off the scale yellow while my drop test results show a chlorine of 4.5ppm.

I’m finding this also true with the ph comparator when I use a meter or Leslie’s for test results.
what could be wrong or what should I be doing differently?

 

[PoolStored]

Trust the drop test.

• The precision of the measurement varies depending on the level being read. At 0.5, or 1 the precision is around +-0.5. At 2 it is around +-1. Above 2 accurate readings become difficult and the precision is very low

OTO Chlorine Test

This test is the most reliable way to check for the presence of chlorine. If … Read more…

www.troublefreepool.com

 

[Texas Splash]

That's a big reason why the FAS-DPD is so important. The comparator is not as specific. Plus, it shows you "total" chlorine, so any CC's are included. Lighting and background colors can also influence the comparator viewing, at least it does for me. When it comes to FC viewing, take it as quick glance to ensure you have chlorine. Not too specific.

On the pH side, it can be tricky for the same reasons. PH meters and pool store testing can always vary. Do your best to be consistent and stick with your own testing results.

 

[Bperry]

My chlorine comparator test results are different from my drop test results. Is this normal or am I doing something wrong? Chlorine comparator routinely shows off the scale yellow while my drop test results show a chlorine of 4.5ppm.

I’m finding this also true with the ph comparator when I use a meter or Leslie’s for test results.
what could be wrong or what should I be doing differently?

The comparator isn’t all that accurate (neither is Leslie’s testing). It’s more for a “do I have any chlorine at all” kind of test.

So you aren’t doing anything wrong other than wasting the time using the comparator test or taking anything to Leslie’s.

 

[reggiehammond]

I pitched the OTO test reagent into the trash after first use. FAS-DPD is the only usable test, in my experience.

 

[dfwnoob]

Yep, tossed the OTO and DPD-only reagent out of my case and threw the salt stuff in instead. The FAS-DPD is the only test I've ever done.

 

[duraleigh]

I pitched the OTO test reagent into the trash after first use.

Of course, you perform the tests any way you like but I find the OTO test VERY helpful for daily use. For the most part it is quite dependable and repeatable.

If you are testing using the FAS/DPD on a daily basis, that's probably overkill but your call.

Probably 80% of my chlorine testing is with OTO.......it works with my regimen

 

[Saturn94]

I pitched the OTO test reagent into the trash after first use. FAS-DPD is the only usable test, in my experience.

Same here. The color matching is difficult for me, so the FAS-DPD is MUCH easier for me to read.

 

[Newdude]

I pitched the OTO test reagent into the trash after first use. FAS-DPD is the only usable test, in my experience.

I started using the OTO for spot checks last year.

The actual # is really pretty irrelevant. The key is knowing you have enough FC to remain clear of minimum tomorrow. My OTO goes from yellow to orange around 9 PPM. At 8 it is a canary / taxi yellow. Running hot as I do, any of the lighter oranges was great. It meant the SWG was doing its thing and if it was 10 or a 12 was a moot point.

For LC, taxi yellow is good enough for today.

*10+ FC invalidates the PH test so I'd make it drift below 10 to do so.

 

[Toxophilite]

I too use OTO on the back porch way more often than bring in water for drop test. I add the chlorine, so just know I need to be above that upper color. But, also, when I periodically shock my well and tank, I run the outside hose and use my trusty OTO until I see a safe level before turning on the house. Here's just today's maintenance after 15 minutes flush.