Hydro ec/ppm clarification please?

Hello and hope everyone is having a great year thus far. Question to my experienced RDWC Hydro growers out there… I’m running a 4 (5 Gallon) Bucket RDWC system with one of the 4 buckets being used as the reservoir. Every 7-10 days I do complete water/nute change out even shop-vac-ing my buckets dry before adding brand new nutriet water. I set my EC to 2500 (I’m 2 weeks into flower) in my fresh nutrient water going in then monitor EC throughout the week each day. What I’m confused over is whether I’m supposed to keep adding nutrient water to keep the EC as close to 2500 as possible day after day or do I just add plain RO water with no nutrients each day until next water change?

Oh and let me add that it WAS 3 plants and 1 reservoir making the 4 bucket RDWC system. Then one of the plants wound up being a male and had to come out leaving me now with 2 plants and 2 reservoirs in the 4 bucket system if that matters for anything.

If you are running 2500 ppm then you are WAY over what the plants will tolerate long term. Vegging plants in RDWC should be around 900 ppm (1.8 EC) and flower would bump up to around 1200 ppm (2.2 EC).

Reservoir size will dictate in many cases how long your solution maintains status: if you could replace the bucket with a 29 gallon tote you can run for a couple of weeks or more with no real issues. Basically your entire nutrient reserve is something like 15 gallons, at best, right now. As root mass increases that will go down. You will also find that a small reservoir will need to be refilled after a couple of days.

No need to post both EC and ppm as they are the same thing.

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Thank you for your response. OK So I put my TDS Pen to EC mode at it reads 2500 when new nutrient water is made/goes into system. I assume then that it translates to 2.5 EC? And you’re telling me I should back that down to 2.2. And try to keep it at 2.2 all week or let it drop till next feeding water change?

An EC of 1 equals 500 ppm NACL scale (American). So, an EC of 2.2 equals 1,100 ppm. Most growers here us ppm to describe their salt levels. You can simply dilute down your nutrient solution with fresh water to the desired TDS (Total Dissolved Solids as expressed in ppm).

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EC if 2.5 is measured in microsiemens, 2500 is expressed in millisiemens. Millisiemens is more precise unit of a measurement and that is what I use.