Calculate total PPM

So I've been reading posts about nutrients (mostly for Hydro growing) and people saying they're at XXX ppm.

My question, where is that number coming from? Are you just using a meter and that's what it says your water is at?

Or is that the sum of all the individual nutrients all added together? N+P+K+Mg+SO4+Ca= XXX ppg?

I'm a homebrewer who knows a thing or two about water chemistry but this is still trippin' me up a bit.

Thanks.

When they are talking PPM (parts per million) refers to salts in the solution. Should be measured after you add fert/food to water. Keep in mind the water before you add anything is going to start somewhere. My tap is 500 ppm by itself and my RO water is 50.

Yep just using a meter that reads PPM, can be a simple TDS meter or something more advanced.

When people talk about ppm on pot forums, it's usually only an approximation based on EC (electric conductivity). TDS meters have a conversion factor which linearly relates EC to tds measured in PPM.

It is not the same as the ppm you're used to in chemistry which is actually mg/liter.

So if someone is making their own formula (like you and me), we will actually know the ppm of each element going in because we put it in there, but if you measure it with a TDS meter, it will probably tell you something completely different than the total of what you put in.

Mattbastard750 said:

So I've been reading posts about nutrients (mostly for Hydro growing) and people saying they're at XXX ppm.

My question, where is that number coming from? Are you just using a meter and that's what it says your water is at?

Or is that the sum of all the individual nutrients all added together? N+P+K+Mg+SO4+Ca= XXX ppg?

I'm a homebrewer who knows a thing or two about water chemistry but this is still trippin' me up a bit.

Thanks.

Click to expand...

This recipe, for example, adds up to around 640ppm of food, but the estimated EC is 1.3mS/cm. With a conversion factor of 0.7 , that EC works out to be 910ppm and with an CF of 0.5, it comes out to be 650ppm.

Oh that's pretty close! Use CF 0.5! for this recipe lol.

So, when people on here are saying they're at XXX ppm, that's the meter reading, but that's not an indication of where actual parts per million but more of a measurement of "shit in the water that supports electrical conductivity"?

If this is the case, is there anywhere I can research recommended actual PPM for specific elements during the various stages of growth?

FYI, I've had a water analysis done at Ward Labs back when I started All Grain brewing so I know where I'm starting, PPM wise, and since the buckets of Jack's say how much to add for certain PPM additions, I know exactly where I'm at on a per element basis.