Astronomically high PPM/EC with Lucas?

Pertinent details:
Plant Age: 21 days since sprout
pH meter: Apera PH60
Medium: Single DWC bucket w/6" netpot. Planted in rockwool with hydroton filler.
Water: I do not have a reliable source of good RO water. I live in a city, but only ONE of the 5 fkin grocery stores has RO water that measures <100 PPM and it's a Walmart that is not exactly near by. My tap is midwest hard and comes out at ~350 ppm/>7.5pH on a good day, therefor it doesn't get used for growing.
Nutes: Lucas Formula GH micro/bloom, Botanicare cal-mag+, Southern Ag GFF


I have a few soil grows under my belt but am new to DWC. I am only running one bucket just to get my feet wet, so I went cheap and easy trying out the "Lucas Method". When I am doing a water change, my PPM is actually PPT and is 1.8, so PPM would be 1800. When measuring EC, I get 2.5. Most of what I have read has been something like 500 to 1200 ppm. My pH/TDS meter is an Apera PH60 that is only a month old and is calibrated as far as I can tell (I calibrated it 3 times before I started using it). My nute measurement is 24 mL micro and 48 mL bloom based on 3 gallons of water in the bucket. Should I recalibrate the meter? Is this an expected level of TDS/PPM?

Secondly, when adding pH up/down, how long do you have to wait for the pH to settle before measuring again?

So, you are using the tap water, right? That's probably the source of your problems, being it's very alkaline to start, which means you are using a ton of PH down to keep it in range. All that PH down is adding PPMs. Also, you probably don't need any calmag with that water, I'd try it without the calmag, and then if you see symptoms, most likely it will be mag that you need, which you can use plain epsom salts for (get pure epsom, no scents). Calmag adds a lot of PPMs. Bottom line, you might have problems doing DWC with tap water, it's not a forgiving medium. As for you TDS pen, it's easy to double check PH, just dip it in calibration fluid and see if it matches. You can do the same for TDS if you have some fluid you know is a certain TDS. TDS pens should not require frequent calibration-you could always buy some distilled water at the store and check the pen against that too.

Rurumo said:

So, you are using the tap water, right?

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Negative. I am using the store bought "RO" which varies from legit RO with ~50ppm to ~200ppm, depending on which store I happen to be near when it is time to refill. I have 4x 4gallon culligan jugs that I refill a couple times a week. I don't even use the tap water for my organic grows. My biggest "worry" about growing with hydro is how wasteful and horrible for the environment it is, so I prefer not to make special trips for water. However, I've already invested this much time into this one chintzy ass plant that now I am going to have to do so.

Rurumo said:

TDS pens should not require frequent calibration-you could always buy some distilled water at the store and check the pen against that too.

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Yea, I have plenty of distilled on hand and make sure to rinse the meter before and after. It always reads 0 tds.

use half strength Lucas (maybe even less?) 4 micro/8bloom per gal
don't need cal/mg with lucas usually

i'd use RO no matter how big a pain it is

LawnXweeds said:

Negative. I am using the store bought "RO" which varies from legit RO with ~50ppm to ~200ppm, depending on which store I happen to be near when it is time to refill. I have 4x 4gallon culligan jugs that I refill a couple times a week. I don't even use the tap water for my organic grows. My biggest "worry" about growing with hydro is how wasteful and horrible for the environment it is, so I prefer not to make special trips for water. However, I've already invested this much time into this one chintzy ass plant that now I am going to have to do so.



Yea, I have plenty of distilled on hand and make sure to rinse the meter before and after. It always reads 0 tds.

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I hope you're not leaving the probe in RO or distilled water very long. It will leach the salts out of the glass ball and destroy the pH probe. Keep that sucker sitting in storage sol'n between uses.

Your Lucas mix seems right but a little high tho I'm not sure what 2ml/L Micro and 4ml/L Bloom should read at but I could go mix up a litre and see what my ppm pen tells me if you want. I have AN and REMO 3-part nutes. I use 1000ppm calibration sol'n to check mine and have 2 so I'm pretty sure I get accurate readings.

My old Hanna pen I bought in '82 and it still works but tends to drift down a little as the batteries get weaker. My newer one is calibrated at 20ppm for use in making colloidal silver so don't like to use it in high ppm sol'ns.

You should think of getting a small RO unit that can be attached to the tap and put away when not in use. A simple 3-stage unit would be fine with potable tap water and probably $100 or less.