0.44 sounds about right, my tapwater is around EC 0.4 although i use RO for an easy life.

kylle221,

Haven't you got any calibration liquid with your buy? If not, stick your meter in some demineralised (distilled) water and compare. I cannot say from here if you perhaps confuse standards instead.

>>Also is the ppm measurement usually not as accurate when using organic nutes?Depends on: first thing to know is that the maesured EC equals the total PPM of soluble ions (salts) there is in a liquid! This includes not only the NPK, but Mg, Ca and a lot of S(ulfur) too. Even some 5-10 PPM of trace elements Fe included. And of course the initial PPM of the water you use, which composition can vary a lot.

Actually, organic matter that is not decomposed yet, will not be included in the measurement, as only dissolved ions and salts are measured. Not sure about how different organic components could (in some case) influence or falsify the EC, though.

Then again, if your organic nutes include a lots of "real" organic matter, that isn't decomposed in ions yet (which I believe is often the case) your EC-Meter can't detect them at all and hence you can't measure them. In that case you must rely on the manufacturers instructions and trust them. Do not forget that with organic nutes you are a way better of if you use a system with lots of media, where microbic activity can take place. I wouldn't suggest deep water systems or any kind of bubblers (with no or little media).

PS: Do not expect bacterial activity and such natural decomposition to take place in a freshly disinfected and sterilised system either ;-)