Chlorine drop test - questions

[pfitz4]

I ordered a refill this morning for my TF-100 kit. My DPD powder is about a year old - it is clumpy and hard to scoop. Will this be at all accurate when I am starting my SLAM today? Need some way to monitor my levels until refill arrives.

 

[mknauss]

If it has been wet it will not be any good. You can try breaking up the clumps and see if it measures the FC you expect from adding LC using PoolMath.

 

[pfitz4]

I’ve been using the old DPD powder until my refill arrives. It seems to work fairly accurately based on my chlorine additions, but repeat tests aren’t measuring exactly the same. Question 1 - Does the size of the “heaping scoop” of powder affect the FC reading?

Question 2 - there is black residue in my test beaker. Does this affect the test, and if so is there a way to clean it out?

 

[mknauss]

You should be using a heaping scoop of powder.

You can usually clean out the test vials with some soap or something. Mine are a mess but I still use them!

 

[cfherrman]

Use more powder, two heaping scoops

 

[pfitz4]

I got the test kit refill today. Did two chlorine drop tests. The first time, I used a heaping scoop of powder, just enough to fill the little scoop with a rounded top. Result was 14 drops (7 FC). I did a second test with a larger heaping scoop and got 17 drops (8.5 FC). I read that you can’t use “too much” powder...is this true? Or is there this much margin of error in the test? Looking forward to your advice to make sure I’m doing this accurately for OCLT purposes. Thanks!

 

[cfherrman]

If you don't have a bit if solid powder in the bottom you didn't use enough.

My 10 g package lasted for 1 oz of reagent from my tf 50 with around 1/2 left to spare

 

[JoeSelf]

^^ What he said. Dave always said to have powder in the bottom. I always check for this.