I'm trying to cool my hydro system and max suspended O2. I have an O2 test kit on the way and will update what total disolved O2 is when I can. My roots are showing a bit of tan where exposed to air below the pots and I'm paranoid about root rot. Also I want to gain the full benefits of hydro which is new to me. What I did was take a 4" inline fan that wasn't helping as an exaust and turned it around. I now have air from the next room feeding the fan which runs down to a 4" bull head tee. From the tee I ran two 4" plenum adapters which are mated to regular net pots. I placed clay balls in bottoms of pots to act as ballast. Overnight the water temp dropped 3 degrees. I believe the airflow across the DWC surface will also improve O2 suspension. All in all the experiment cost about $25 since I already had the fan installed. The pics below should carify my rig. I hope this trick helps folks out. Should really be good with small tents and such.
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HYDRO Cooling water by direct air injection into DWC containers
- Thread starter KoolKat
- Start date
DW2
New member
Howdy KoolKat, What are the reservoir water temperatures with the air injection? I have been using four outlet air pumps with four, four inch by two inch air stones in six gallon reservoirs and have noticed some things to watch out for. Air is only around 21% O2 and about 72% nitrogen (CO2 and other gasses making up the rest) so one must watch for nitrogen toxicity in the plants. Air will not transfer a great amount of heat (or cold) when compared to a denser medium such as water or other fluids. Pushing enough air into the reservoir to lower the temperature could cause problems with the nitrogen and pH fluctuations due to dissolved CO2. The air pump that I use is listed at 254 GPH which calculates to .5659 CFM and this causes some 'clawing' and signs of nitrogen toxicity. I have been using 0.7 l bottles of ice to maintain the reservoir temperatures between 60° F and 70° F. The time between changes varies with the ambient room temperature, in cool weather the bottles can last up to 10-12 hours between changes. I also wrap the reservoir bases with bubble wrap to provide a small amount of insulation.
Nitrogen gas? Never thought of that. I'll watch for it. Everyone seems to think there's no such thing as too much air. I will be testing O2 levels. Supposedly about 9% is ideal and about all u can do without super saturation. I also just got a TDS, EC, TEMP meter. Hardness is 90, much better than I feared. I understand that EC will tell me about my N levels.
Obi-Wan
New member
Most DWC growers won’t see any negative results to the increased nitrogen that it added through air. Atmospheric nitrogen is not immediately available to most plants grown in DWC because the solution lacks the bacteria to complete the chemical bonds necessary for the plants to use it, rendering it unavailable. Products like Great White that contain mycorrhizae and other microbes will make some of this nitrogen available but a salt based nutrient solution will always hold back large enough colonies from ever being formed. More air is better for the roots preferably with good surface agitation
DW2
New member
Looks good! I once told someone that 'the only way to put too much air into the reservoir was when it blew out all of the water!' I feed the nutrients (GH Max series) at the maximum recommended levels, which mat account for the 'nitrogen toxicity' that I have encountered on past grows. You mat be onto something there, Turbo aeration!
Week 10 just begun. I cut back on air flow hours, now running off light timer. Had a cold snap and without AC humidity shot up to 70%. Water was evaporating fast too. Since air is being injected throughout light cycle I've seen no temp changes. Room air 73, supply room air 70, Water temp 68.7. Ph has remained rock solid at 6. Roots are looking cleaner and whiter as well. So far this experiment has been a success. Tent growers check this out, perfect for confined space and budget, maybe 100 bucks including fan and fittings.
FYI I'm using GH flora series with floralicious + and hydroguard - so there is some organics and microbial action present.
FYI I'm using GH flora series with floralicious + and hydroguard - so there is some organics and microbial action present.
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HappyDaze
New member
I've set up similar cooling for my DWC grows...3" 9V cooling fan from a computer fit to a 3" net pot sitting right below the canopy running 15 on / 15 off during lights on, works great. The heat generated from pumps is why I never bothered with any RDWC....DWC works as well or better if you have a big enough air supply and distribution to generate some surface spray in the rez. KIS
I agree about the KISS principal. I had issues throughout the 3 weeks or so that the water pumps ran, and with all those roots I'd probabbly kill my girls trying to get to them now. I'm going to bite the bullet and get a chiller soon. I'm paying at least $100 a month in extra A/C so it will pay for itself. Since I will have to have a pump for the chiller I'm planning on an external one and tapping off enough flow to ensure the pots stay wet during startup. Please note I am venting air from another room to the tanks, so it is cooler and fresher than the grow room air, still what you did ought to help your res temps. I also don't like the grow room so cool. 73 works but 75-80 has always worked best for me.