I bought a GH and KH test kit today. It is the API test kit. I put one drop in at a time and neither solution changed colors after 12 drops. I know I have really hard water but should I have seen some kind of change? I did the test on just tap water.

My API GH test kit stopped working after about 18 months, so it could be that you just have a bad kit. My KH kit still works, or it did a few weeks ago when I last used it. The first drop of reagent should give you one color, and the next drops eventually change that to another color. As you add drops the first color usually gets a bit more easy to see, before it changes. Did yours act anything like that?

I got the one color but it never changed colors. I think if I had kept adding drops it would have eventually changed I guess I should have kept adding drops

You probably just have high GH and KH. When my GH kit quit, I didn't get much of any color with the first drop, and it never did intensify with additional drops, nor did it ever change color. A new kit worked as advertised.

Okay thanks. I wonder if my local utility would do the test using their equipment if I took a sample in. LoL Guess I will call and see.

Make sure that you are looking for the right color change. Since my tap water is so soft, it never changes either; because the first drop brings it right to the second color. 0GH and 0KH. A trick to remember which is which: The second color will be similar to the color of the drop before it actually hits the water.

Yea I am sure I was looking for the right color. I just did the KH test again and it took 17 drops to get it to change color. Just some really hard water. Okay so I understand KH as the amount of Carbonate HCO3. What is the GH then? General Hardness yes I understand that but what is its chemical structure or what is it measuring?

Ca and Mg ions.