you can compare the vials by doing a "test" using each with ro, no reagent. I've ran it a couple of times, different order and always get zero.

I always use a tissue to grab the vial. Finger prints are enough to throw the whole reading away. Alongside, one tiny floating particle in the vial is also enough to give you false reading. And the worst part is the 3 min shut down time. I don't know what the people at hanna was thinking? I guess according to them, its "cost effective" to throw away a dissolved solution than to change a battery for adding an extra minute to the shut off time, not to mention the dedication to pour the powder in and the two minutes shaking time. I really hate this photometer from the bottom of my heart but well, if I get everything 100% right, I know I am going to get a much more reliable reading than any other test kits. But reaching the 100% takes a lot of work and luck too.

so you zero with one vial and have the other mixed?

why else would they give us two lol?

Geez guys, it is really not that hard... I only use one vial, and always get it completely mixed every time. Like I said, just have to do it right as described above, and it is then very accurate and consistent.

+1

my readings sometimes vary so it's good conversation to me. if there's ways to make the process more accurate it's worth discussing.

when I started and was slow with the Hanna was using both vials. Now do the C1, add reagent, shake, hold the button to get the 3 minute timer started then done. Seen a video where you crease the packet to get a funnel helps to pour.

i wish hanna would sell a little canister with spoon similar to what elos does.

I wish they'd just increase the automatic off time to five or ten minutes. I also wish they'd use a method that isn't so finicky to tiny variables and would be more consistent.

Having said that the phosphorous ULR checker does seem to be pretty reliable for me. It uses the same process as the phosphate but measures phosphorous; then you do some simple math to estimate your phosphate concentrations.

Maybe I'm slow, but I cannot fill vial, add ALL the reagent in the pouch, and completely mix it in 3 min. At the end of 3 min I still have solid particles of reagent swirling in the vial. I don't want to measure it unless it's completely dissolved. That's why I use 2 vials.