Water analysis

[King_of_orchid_growing:)]

BTW I apologize for any badly written sentences and poor grammar, I wasn't checking.

[Corwin]

So if I understand you well, my GH is OK but my KH is not

I'll check the rainwater

[King_of_orchid_growing:)]

Not quite. Generally speaking you have hard water.

If the water from your tap water has a CARBONATE HARDNESS (dKH) of 8 dKH or 10 dKH, it ONLY measures the amount of CARBONATES AND BICARBONATES in the water.

HOWEVER...there're MORE dissolved matter in water than JUST CARBONATES AND BICARBONATES. Other minerals must be accounted for SUCH AS CALCIUM and MAGNESIUM. All the other dissoved minerals and salts are accounted for in a measurement of GENERAL HARDNESS (GH).

So...

If your water has a CARBONATE HARDNESS of 8 dKH, it's very likely that your GENERAL HARDNESS IS HIGHER, say for example 10 dGH.

[King_of_orchid_growing:)]

ppm stands for parts per million. For example, a measurement of 142 ppm of food coloring in your water is saying...

For every million drops of water, there's 142 drops of food coloring in it.

[King_of_orchid_growing:)]

I made a small mistake about the general hardness. General hardness apparently is measured in parts per million (ppm) not dGH. Oops...

[Corwin]

I just read that KH is removed by boiling the water (?)

I'll give it a try

[harrywitmore]

The test strips I have measure bot GH and KH in ppm. This is a very good thread!

[buckie]

I sorry I didn't know that your tap water quality over there was that bad, here in Australia the water is treated to a set standard, yes there is differences from state to state but not by enough to worry most people.

Warren

[Corwin]

Well I did mention that it was water + nutrients in my first post... I guess I forgot about that

I just did the test for the third time and it looks like the KH of the water (without nutrient) is 6. Is it possible for an 3-4-5 NPK orchid fertilizer to change the KH that way? Or are my strips just changing color because of moon activity?

By the way... the pH is up to 7,6

I think I'll buy demineralised water (or at least boil my tap water)... I've only got 2 orchids so far so it shouldn't be too expensive

[King_of_orchid_growing:)]

I can't tell you how adding a fertilizer would affect the hardness of your water. It probably won't make the water softer. Then again, that's a guess. I don't know the specifics of the chemistry behind that, (I never bothered to understand this because it wasn't ever an issue). Again, I'm assuming that adding the fertilizer won't soften the water up.

However...adding the fertilizer will most likely affect the pH of your water. It's likely it will lower the pH of the water because of the nitrogenous compounds in it.

pH is actually relatively easy to change. Like I said, the pH of water can change pretty often throughout the course of a day. This is why when you speak to advanced tropical fish hobbyists they will often tell you to not test so frequently for pH.

I will also note this...

Let's say you have a beaker half filled with water that has a pH of 8.2, and you add an acid (let's say one third a cup of lemon juice), then stir...

You cannot take a sample of water from this beaker right away and test for any changes in pH. The chemical reaction needs time to occur.

Remember that link you posted about KH, GH, and pH? There's a formula in there that shows you how pH works, (the problem is it's a math equation with numbers and most people don't understand what this means).

Basically pH is a logarithmic function, (a base 10 function to be more specific). What this means, is that any kind of change that happens will not be linear.

This is what I mean by linear:

1+1=2+2=4+3=7

or

7-5=2-4=-2-3=-5

Logarithms work differently... We're talking about exponential growth and decline here. The simplest way to understand how this works is bacterial proliferation.

Assuming that each bacteria will split into two bacterium (an exponential power of 2), the following is a simple illustration of a logarithmic function and therefore exponential growth is this:

1 bacteria splits into 2 bacterium

2 bacterium splits into 4 bacterium

4 bacterium splits into 16 bacterium

Now, it's been a while since I've learned chemistry so I can't go into too much detail as to the specific workings of pH unless...someone here in the forum is better versed at it than I am (please chime in, please, oh please, I think I'm starting to get in way over my head on this one). But practically speaking, back to basic understanding of pH testing...

Because of this logarithmic function of pH, it will go from an initial gradual change and spike enormously. pH will then start changing again until it settles. Without the ability to draw a graph I can't demonstrate the actual changes of pH.

Suffice it to say, if you did graph it, it will look like how a graph for the stock market would be (it's not exact, but somewhat similar).

For this reason, it's not advised to keep testing for pH too closely between testing intervals and too soon after a physical change in pH (like the example of adding lemon juice to water). It'll drive you crazy.

BTW, this is what those pH meters do. They test for a sample in time. If you did an experiment and tested the pH of water over a period of 1 hour using the meters, for every 5 minutes within that hour and graphed it, you'll see what I mean.