CC and algae in test tube not pool!

[Pins]

Hi all. Have been SLAMing my pool for about 2 weeks and OCLT seemed to have settled but CC was well over 1.5. (SLAMing because we went away and someone forgot to turn the SWG back up before leaving!)
I noticed the test tube had black marks on it but thought it was just scuffing from the mixing button…even though none of my other tubes have this.
When I ran a test side by side in a tube without the black marks…hey presto, CC was zero!!! Crazy!
So it seems that perhaps algae had actually built up in the test tube and then CC was showing up.
The message is make sure tubes look squeaky clean when testing!
In the photo, exactly same pool water result testing for CC. Dirty tube on the right! Even the red colour looked really dark in the dirty tube compared to a cleaner red in the clean tube. Hope this helps anyone else out there getting strange test results.

 

[ajw22]

Cleaning Taylor test sample tubes

Any suggestions? I have 4 and some are getting gnarly

www.troublefreepool.com

Water Testing Errors - Further Reading

www.troublefreepool.com

 

[Mdragger88]

The dpd powder can/will stain the tube over time (and anything else it come into contact with that may get wet). It’s probably not algae. Cleaning it with alcohol & rinsing well will do the trick.
Cc interference can be a problem with a dirty test tube

 

[Pins]

The dpd powder can/will stain the tube over time (and anything else it come into contact with that may get wet). It’s probably not algae. Cleaning it with alcohol & rinsing well will do the trick.
Cc interference can be a problem with a dirty test tube

Squeaky clean test tubes is the moral of the story. I might try and buy one of those little tube brushes. Thanks for the extra thoughts.