Nutrient question already searched Google

OK this might have been asked before but it seems like a answer is no where to be found. You always hear people talk about pppms and what's ppm range they use. Are these numbers before or after they add in what ever extra stuff they might use like orca or rhiztonic or anything that is not a nutrient? I have yet to find a good breakdown just a lot of this many ml per gallon of this and that

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In general, readings should include everything in solution (so after everything is added) because most additives will have an effect on the total nutrient strength.

TDS or ppm's are such a bad metric to use however, because they just results in a lot of confusion due to not being exactly accurate. Since TDS (ppm's) is based upon EC (electrical conductivity) and different places in the world use different conversions for guessing what the ppm's are based upon an EC reading... and people rarely state what conversion factor they are using or other important information you might need to know like what the starting EC/TDS of the water they started with is. Or in other words, TDS is mainly just a ball-park thing anyway (arguably even less useful than just using a universal metric like milliliters when sharing information).

Wish more people would just stick to using EC though - not sure why the whole TDS thing became popular with hydroponics.

Ok because this is my line up in Veg right now and I'm at a1.0 ec and a 6.0 pH. The Dyna I use 3 ml in a 5 gal bucket and cal mag at 2ml in a 5 gal bucket.
Forb someone reason I can't post pics right now

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SableZen I have a under sink filter which takes water from the same source as the faucet, when I read the filtered water it shows 10 ppm over he faucet 155 to 165 after running both for 30 min. it reads 125 to 135 same 10 points above. The meter zero's out in distilled water and all three filter cartridges are new The filtered water taste better so something is working in the filter. Does the charcoal filter add ppm to the water? I'm asking you because you seem to have the questions of water down Denris

jallen156 said:

Ok because this is my line up in Veg right now and I'm at a1.0 ec and a 6.0 pH. The Dyna I use 3 ml in a 5 gal bucket and cal mag at 2ml in a 5 gal bucket.
Forb someone reason I can't post pics right now

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That's a sane EC and pH for hydroponics - a lot of people stay around 1.0 EC with mature plants. Some push the limit with nutrients/additives, some don't - depends on your setup and process (like how often, or if, you change the reservoir out throughout the grow or if you do any sort of add-back as EC drops, different strains uptake more than others, stage of plant growth, etc).

You could drop the pH just a hair - say like to 5.8 or so (again depending on variables like whether your reservoir pH tends to trend up or down) - but 5.8 is a good pH to shoot for in general and 6.0 isn't bad at all.

denris said:

SableZen I have a under sink filter which takes water from the same source as the faucet, when I read the filtered water it shows 10 ppm over he faucet 155 to 165 after running both for 30 min. it reads 125 to 135 same 10 points above. The meter zero's out in distilled water and all three filter cartridges are new The filtered water taste better so something is working in the filter. Does the charcoal filter add ppm to the water? I'm asking you because you seem to have the questions of water down Denris

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I use a carbon filter as well and yes, washed out carbon from the filter will increase the EC/TDS at first (especially if you don't rinse the carbon filter well before use). Additionally though, I've also read that carbon filters also tend to leave the water positively charged which would slightly increase EC/TDS readings. I'd bet if you checked with the manufacturer (or the website) of the carbon filters you own they would be able to confirm that.

Im only a newb on here but after some extensive reading, i must admit, this whole ppm thing is doing my head in!!!

im a pool cleaner and a aquarist so deal with water ALOT! its quite annoying to see people throwing around terms like ppm without really knowing what that is. as far as i can tell, on this forum people seem to use the term "ppm" (parts per million) in place of the term "TDS" (total dissolved solids)

Now, TDS is measured in ppm, so theryre actually correct but it might be a bit confusing for some newbs when they read these posts and dont realise what particular parameter people are measuring. i found myself asking "ppm of what?!?!?, TA?, KH?, GH?, TDS?, N?, P?, K?,...etc etc " a few times


Denris- as for your readings, the only thing i can think is that carbon dust is contributing to the higher reading, and will stop doing so once its been thouroughly flushed. ive never heard of carbon adding anything to water unless its "full" then it does start to dump the contaminants back into the water its meant to be filtering! so its wise to change them when reccomended.

Here's a chart I'm copying/pasting:


It kind of explains things without going into the math: Your meter starts by measuring the EC of the solution, it then mathematically applies either a NaCl or 442 conversion (N. American meters tend to use one conversion and Europe tends to use the other for some reason) to guess at what the parts per million of anything in solution is.

My question would be why we bother with TDS at all though? Why not just go with using the EC since there is a significant difference between both the NaCl and 442 conversions and hydroponic solutions aren't going to be completely similar to either NaCl or a 442 solution... so the results in ppm aren't going to be accurate in parts per million anyway. And besides, it's unnecessarily confusing.

Thanks; It made no sense, I thought I was wasting my time with the filter Denris

SableZen said:

My question would be why we bother with TDS at all though? Why not just go with using the EC since there is a significant difference between both the NaCl and 442 conversions and hydroponic solutions aren't going to be completely similar to either NaCl or a 442 solution... so the results in ppm aren't going to be accurate in parts per million anyway. And besides, it's unnecessarily confusing.

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exactly!

like i said im new to growing but arnt we primarrilly concerned with concentrations of N, P, K and trace elements when we do these tests? none of which have got anythuing to do with NaCl!!!

there are test kits for these individual elements if you wanted to be uber-precise with your dosing. dont people just buy ferts at a specified ratio eg 30-10-10 etc, then mix it with however much water it says to, and voila! why do we need to test at all?

please let me know if ive got the wrong end of the stick here...

crete said:

exactly!

like i said im new to growing but arnt we primarrilly concerned with concentrations of N, P, K and trace elements when we do these tests? none of which have got anythuing to do with NaCl!!!

there are test kits for these individual elements if you wanted to be uber-precise with your dosing. dont people just buy ferts at a specified ratio eg 30-10-10 etc, then mix it with however much water it says to, and voila! why do we need to test at all?

please let me know if ive got the wrong end of the stick here...

Click to expand...

Yeah exactly - it would be a different story if there was a universal conversion that hydroponic meters used to guess the ppm's based upon some sort of ratio of NPK in solution. But what we have instead is a conversion based upon NaCl or 422 solutions to guess at total TDS/ppm in general. So as it is, it just makes more sense for us, mixing up parts of pre-made nutrient solutions and additives, to use the more universal EC metric when sharing info with others (in order to be more accurate and avoid confusion arising from different conversions).

I mean EC/TDS is still important to an individual to understand what's going on in the reservoir and how much a plant may (or may not) be uptaking from the solution - it's just not as great of a tool for sharing information except for ball-parking things since there are so many variables between growers, plants, setups, etc on top of not exactly being very accurate in the first place.