When MegaCrop says "X PPM" is the right dose, do I subtract the PPM in the plain water first?

[Auto-Bud-Man]

I was checking my PPM of my nutes this morning and a question came to mind: when GreenLeaf says "500ppm" is a the correct dose at a given point, does that mean that I should add the 200ppm that my plain water has right out of the tap and add nutes until the measurement reads 700ppm instead?

 

[Proph]

You would substract the "plain water" ppm from the final mix ppm to get the true ppm of the nute solution. If your plain water ppm is high, you may want to use a different water source.

 

[Proph]

So your total ppm should be 700.. 500 recommend, plus the 200 from plain water

 

[Auto-Bud-Man]

So your total ppm should be 700.. 500 recommend, plus the 200 from plain water

Thanks...that clears it up.

 

[Qwin08]

@Greenleaf Nutrients are you and prophetiko really saying the same thing?
*EC is additive, so you measure your base water EC then add in the suggested amount.
For example: Base water EC .2, suggested dosage is 1.1, then final level will be 1.1 + .2 = 1.3