Warrioreuel
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Any time the water is slightly acidic, it will cause concrete or cement to offgas, especially newer cement that takes a few years to fully cure. Salt will do the same as it dissolves cement slowly, as evidenced by sidewalk damage that happens when salt is applied, engraving the surface. A simple CO2 removal system that is dirt cheap to use is simply an air pump and a large 5-6 gallon or larger container, filled with water. Add a bunch of Calcium Hydroxide to the water. The water should turn clear. Pump the CO2 laden air thru the Alkaline water, and the CO2 will precipitate out as Calcium Carbonate, which is insoluble in an alkaline solution. The solution needs to be recharged every so often, but Calcium Hydroxide is pretty cheap and known as Caustic or pickling lime. The final product, known as Limewater, causes CO2 to precipitate out of the air when pumped thru it.Yes, the new concrete is looking more and more like the culprit. And yes, the concrete even though finished nice and smooth it seems very porous to water. I guess i could water it down and verify one last time the CO2 level shoots up. Long term fix, painting is in order. Short term i reluctantly will dismantle the equipment and put down plastic. It will take a week or two before i have (no pun intended) any concrete results but, i will let you guys know the verdict. In the mean time I still want to test removing CO2 from the air since i have the absorbent material on its way. Wonder how long the concrete would naturally stop off gassing or sinking CO2? If its porous, maybe never? Or maybe several years making it impractical to wait it out.
But they are respiringIn his book Ed Rosenthal mentions that at night plants release co2. This is why he recommends not adding co2 with an external system for the first hour or two of the lighter being on.
Edit: my 2 cents is that as long as it goes down during the day you are good. If the lights arent on the plants are not performing photosynthesis therefore not taking in co2.
Now that you mention it I think the problem was the opposite of what I thought and that makes more sense. With my timer starting and stopping that would mean during the day period I would have no CO2 at times and that was more likely the problem rather than the high night times. Those symptoms fit the bill. Here I thought it was the night time levels that caused it because that when I noticed. I kinda feel foolish now.In his book Ed Rosenthal mentions that at night plants release co2. This is why he recommends not adding co2 with an external system for the first hour or two of the lighter being on.
Edit: my 2 cents is that as long as it goes down during the day you are good. If the lights arent on the plants are not performing photosynthesis therefore not taking in co2.
I use a timer and controller but most controllers have a light sensor. I would make sure to run a controller for the simple reason if wasting CO2. Also you really only need to run it beginning of flower until about 2-3 weeks before harvest unless you are supplementing at which point 500-600 ppm is more than enough for the rest of the time.I am interested to hear if the co2 absorbent works out for you. What are symptoms of co2 poisoning? I am installing a sensor and co2 regulator in my grow. I will definitely be looking at the nightly number. I wonder if the co2 in my tents will raise that much.
You mentioned a timer so I'm guessing you have a tank and regulator right?
Concrete does capture co2 by a process called carbonation.Thank you for all replies. This is a metal building I had built. Poured the concrete slab 1 year ago to date. There is no controller or CO2 tank in the room at all, i removed it until i figure out what is going on here. It has 12 seedlings a few inches tall. However, there is 120 gallons of water circulating in a DWC setup with Cal-Mag, Aqua Flakes and nitric acid to keep the PH just under 6. It also get about 150 ml of UC roots once a week to keep away root rot. Since the seedlings are small my nutriet strength right runs approx 120 ppm. This is not my first setup but it is a new grow room in a new area so to speak. The RO water by itself is almost exactly PH 7 with 20 ppm, so its pretty clean. At this point my list of suspects (process eliminatus) is the concrete is off gassing CO2 (or poured on top of a CO2 source bubbline through the floor), the OSB walls, the paint and now possibly the nutrients in the water off gassing (had not thought of that before). So far i have left the door open now for a week with a floor fan and the levels are down to low 400's. If I close the door they will rise so as a stop gap measure i will simply leave the door open for now. CO2 absorbent media hopefully be here this week. When it gets here my intention is to route the air through it before it bubbles through the air stone. I am hoping that this will least scrub my water of CO2 which was most likely saturated with CO2 gas when the room was 3000 ppm. It would be nice to have a device to check to dissolved CO2 level in the water to see if I am actually having any impact with my corrective measures. I suppose recovered healthy plants will be the final indicator but I like to know really what is going on. I suppose if this were a dirt grow then the free CO2 would be fine. But, in hydro it is poisoning my water.
Here are some questions. Is an OSB walled painted with latex a true barrier for CO2 or does it pass through the wall as if it were nothing more than a bug screen? Does concrete retain CO2 like a sponge? In other words when my levels were over 3000 ppm, did the concrete absorb this and now slowly releasing it?
Bugs aren't bothered too much by high CO2 levels... they just sort of fall asleep and wake up as soon as the air is OK again. I had some bugs in a somewhat similar situation where I couldn't use any type of spray and the CO2 looked like a good idea. Dutifully, the bugs all fell over after the CO2 introduction and stayed that way for a few hours. As soon as I vented the stuff out, they yawned, rolled over, asked what time it was and got back to their destructive business. I thought cockroaches were hard to kill... Mites are so small that you don't even know you have them until the damage shows up... cockroaches are big enough to see and stomp on.I poisoned some planted a few years ago when i experimented with intentionally raising the CO2 level to 5000 ppm to try and kill mites. Side not, don't bother doing that, it is a waste of time and will injure your plants.
Yup I set mine to reach max ppm in an hour when the room is empty of plants. Allows for dispersal and equalization of CO2 so you don't get that creep after it shuts offLittle more side info while I am waiting on CO2 level results.Yes, i use tank CO2 with a standard little solenoid valve controlled by an Autopilot APCECOD CO2 controller. It turns itself off at night and works perfect. Key to getting good results - adjust your release rate on the tank regulator so the little green ball in the sight window is super slow. For the first year or so i thought this controller was a real waste of money. Turns out i was using is it wrong or more precisely had the release rate of the CO2 way way way too fast. Once you understand how this thing works it will make more sense to set the release rate to a real slow rate. This gives the CO2 time to disperse and equalize in the room rather than the blasting it out at full speed which drives the sensor crazy. As I mentioned before, right now the entire CO2 system controller and tank is completely removed from the room. Not able to test the media yet as one part did not come in yet. I could just pour it in a bowl, close the door and see how it does. But. what i want to do is actually run the air through the media just before bubbling it into my water. If the air bubbling through the water is void of CO2 this should help cleanse the water of any excess if there is any. Without being able to measure dissolved CO2 in water I am assuming that when i was bubbling 3000 ppm levels that the water could be CO2 laden. How fast the water releases this to the surrounding air i can only guess. The door to the room is still open, floor fan running. Todays level was 420, still higher than normal air. My meter works fine, took it outside in open space and it checked in at 379 ppm.
I use a timer and controller but most controllers have a light sensor. I would make sure to run a controller for the simple reason if wasting CO2. Also you really only need to run it beginning of flower until about 2-3 weeks before harvest unless you are supplementing at which point 500-600 ppm is more than enough for the rest of the time.
I use a timer and controller but most controllers have a light sensor. I would make sure to run a controller for the simple reason if wasting CO2. Also you really only need to run it beginning of flower until about 2-3 weeks before harvest unless you are supplementing at which point 500-600 ppm is more than enough for the rest of the time.
Digging deeper into the curing process, hydration is the chemical process that allows concrete to go from a plastic state to a hardened state while gaining strength over time. Hydration occurs at a faster rate in the early stages after concrete placement and slows down after a month or so goes by. Many cement pastes will cease hydration before one year, and some may continue to hydrate over the course of several years (4). Because of the variable length of the hydration process, the phrase “green concrete” is a purely subjective characterization.
It would also be interesting to know what the chemical composure of the lot/soil is under the slab. Even when concrete is fully cured it remains slightly porous. My theory is something under the slab, maybe vegetation going thru decomposition allowing it to rise thru the capillary matrix in the slab raising C02 levels. Along with the fact the slab is still so new.
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