Measuring EC / PPM in a flood and drain system

subwax

Well-Known Member
I run a flood and drain setup with a res, one control pot and 4 grow pots. For the most part, it really is a walk in the park. Easy as you like. The exception for me is the measuring of the EC. I have both a Blue Lab PH Controller as well as a Blue Lab Guardian, so I am always closely monitoring and recording my statistics. The one thing I struggle with is EC, and the reason is - it is always rising. I try and try to get that magic sweet spot, where the PH and ED is static, with water level dropping. For the most part, the EC is usually rising. Take now, for instance - I am at week 7 of a 4 plant 7 week grow. My EC is down to 1.4 / PPM is 1000. currently. My tap water EC, once filtered is around 400 ppm / EC 0.6. I flushed a few weeks ago, and the continued its rise, even with clean water. I change my res every 7 days.

I haver read that with static water uptake, and figures rising, an increase in EC would be needed. In all other cases, increasing EC means a drop is needed. My water levels are dropping, so if anything, I'm supposed to drop the EC.

The plants are growing well - might have been a bit heavy handed with PK earlier in the grow, but plants showed me to back off.

Anyone else have issues like this?
 

SofaKingHigh_

Well-Known Member
I run a flood and drain setup with a res, one control pot and 4 grow pots. For the most part, it really is a walk in the park. Easy as you like. The exception for me is the measuring of the EC. I have both a Blue Lab PH Controller as well as a Blue Lab Guardian, so I am always closely monitoring and recording my statistics. The one thing I struggle with is EC, and the reason is - it is always rising. I try and try to get that magic sweet spot, where the PH and ED is static, with water level dropping. For the most part, the EC is usually rising. Take now, for instance - I am at week 7 of a 4 plant 7 week grow. My EC is down to 1.4 / PPM is 1000. currently. My tap water EC, once filtered is around 400 ppm / EC 0.6. I flushed a few weeks ago, and the continued its rise, even with clean water. I change my res every 7 days.

I haver read that with static water uptake, and figures rising, an increase in EC would be needed. In all other cases, increasing EC means a drop is needed. My water levels are dropping, so if anything, I'm supposed to drop the EC.

The plants are growing well - might have been a bit heavy handed with PK earlier in the grow, but plants showed me to back off.

Anyone else have issues like this?
It possibly could have to do with how you mix your nutrients and what you are using to bring your ph down. Look into different solutions for lowering or raising your ph. Most have to ph down I’m assuming that’s what you do.
 

Thundercat

Well-Known Member
I found running 7-800 ppm made most of my plants much happier in my flood and drain then trying to feed heavier. I've had genetics that could take heavier feeds, but not everything needs it.
 

ComputerSaysNo

Well-Known Member
I don't quite understand what the problem is (especially since the plants are growing fine, as you say).

The plants will never use the nutrients at exactly the same rate as the water evaporates. So your EC (= nutrient concentration) has to change over time. If the water is used up more quickly than (some) of the nutrients in it, the EC will naturally rise.

If you ran a setup with no plants in it, you would end up with close to 100% nutrient concentration just before the last drop of water has evaporated.

Change the reservoir occasionally, and do not top up with full-strength nutrient solution. That is pretty much all you can do to counter this effect.

The plants will definitely not use all the minerals at the same rate, so the longer you recycle the nutrient solution in the system, the more imbalanced it will become.
 
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