View Full Version : API CA & Alk test experiment results--can you add multiple drops at one time?

02/07/2013, 07:02 PM
I ran an experiment today testing my water. With the API CA & Alk tests, the directions say you add drops individually and shake between drops to see when the water changes color.

I was curious if you can add a bunch of drops at a time (if you estimate that your CA or Alk is at least a certain amount) and then add one drop at a time until you get the color change.

Here's what I found, when I added 7 drops individually with shaking between the drops I got the color change for Alk. which was the same as adding 6 drops (then shaking a lot) and then one more for the change. Alk = 7 either way.

When I did this with CA, I got 17 drops (340) when done individually with shaking between but 21 (420) when I added 15 drops at one time, shook a lot, and then added drops individually.

There should NOT be a difference like this with the CA tests should there? OR is it important to slowly add the drops with shaking between?

I'm wondering if I lost a tiny amount of solution from the cap dripping between drops when I shake between individual drops.

What are your thoughts about whether multiple drops is just as accurate OR my quirky results???

02/07/2013, 07:16 PM
I used API a while ago, and I used to do multiple drops for Ca, putting something like 16 drops in at once, then I'd start doing one drop at a time when I was closer to my expected Ca level. This kit isn't terribly accurate, but I didn't have readings that were horribly off. For your alk, I'd only about 5 drops at once before switching to single drops.

02/07/2013, 09:38 PM
when i was young (lol) i used to use api cal. and i did add 5 drops at a time till 20 drops which is 400ppm as i knew my cal was always 440-460 range.
but if u do add a bunch of drops make sure u mix it well before continuing.

02/08/2013, 01:43 AM
I don't know enough about that particular test kit to say much, but you can add multiple drops for the Salifert kit, and likely most others, if you shake for long enough afterwards, and give the reagent some time to react.

02/08/2013, 02:10 AM
I see no difference in API tests when doing multiple drops, but I use a cuvette from a JBL test because the original canīt be shaked properly. API and JBL give me same results but I prefer the first because in the second one indicator doesīnt work after several months.

I think your problem is the cuvette.