CYA test with Hach DR/850 Colorimeter

hamop78

LifeTime Supporter
Mar 29, 2007
18
Central PA USA
As everyone knows the CYA test in the Taylor kits leaves a lot to be desired. Recently I found a Hach DR/850 Colorimeter ($20.00 at a public auction --- Local lab went belly up) . I bought the appropriate reagent from Hach ($17.00 for 50 powder pillows) and ran my first test using both methods. I was amazed at the differences in the results.

I have both the Taylor kit and the Rainbow lifeguard, both showed <20 PPM but the Hach colorimeter result was 35 PPM. I ran a standard using the method in the Hach procedure manual and zeroed the instrument.

Which result should I believe.

This instrument is way over kill for the pool but I wonder what other tests (Pool related) it might be good for.
 

JasonLion

TFP Expert
Platinum Supporter
LifeTime Supporter
May 7, 2007
37,880
Silver Spring, MD
The Hach Colorimeter claims that it can measure CYA from 7 to 55 and is +-1.2 at 25. They don't mention this, but they would obviously be less precise near the ends of the range. The Taylor test measures CYA from 20 to 100 and is +-10 through most of that range, though novice users are often more like +-15 or even +-20 because of difficulty in interpreting the test results. Palintest makes meters that claim a test range for CYA of 0 to 200, though they don't appear to make a precision claim.

The range on the Hach test is rather narrow. Also, colorimeters typically have trouble with turbidity tests and I find their precision claim difficult to believe. The ColorQ is based on similar technology and it is far less precise than the Taylor test.
 
G

Guest

The LaMotte waterlink express colorimeter has a range of 0 to 150 ppm with an accuracy of +10/-25 ppm. My experience with this unit is that it consistantly measures low compared to the Taylor test. I tend to beleve the Taylor test.
 
G

Guest

Hach and LaMotte both make excellent colorimeters if you want to spend about a thousand dollars or more. Not really sure on Palintest's pricing.
 

hamop78

LifeTime Supporter
Mar 29, 2007
18
Central PA USA
Thanks for the input

The accuracy range of meter is where I like to keep my pool 25-35 so I'll do some further testing to see how it goes.

None of the pool stores in the area can produce acceptable results and have even detected up to 20 ppm in a sample of distilled water I took them :twisted:

I have reagents for 50 tests so.......could be an Ebay item in the future. I'm certain I can get my 20 bucks back.
 

mchristisen

Member
Apr 14, 2008
5
Austin, Texas
I purchased my Lamote ColorQ Colorimeter for about $250.00. While most test results mirror the Taylor, the
CYA is way off. Just today Taylor gave me a CYA of 60 while the ColorQ gave me 13.
 

Sabot

LifeTime Supporter
Aug 2, 2007
343
Austin, TX
The ColorQ CYA testing on my unit is just as bad as the Pool Store reading. Weekly, I test using the ColorQ vs TF100. Friday's CYA reading on the ColorQ was 6 and TF100 was 40. The week prior I took samples to two differant pool stores and my CYA was about 50 on average. (Both store reading where off...)