How to keep your reservoir cool

Discussion in 'Hydroponics / Aeroponics' started by mogie, Mar 21, 2007.


    mogie Well-Known Member

    Maintaining a highly aerated root zone at optimum temperature is key to achieving high yields and problem-free grows. This FAQ focuses on indoor hydroponic reservoir cooling options.

    Why do I need cool root temperatures?

    High root zone temperatures often plague indoor growers running water culture (aero/bubbler/dwc/hydro) systems. These systems are subject to rapid heating by intense HID lighting, which increases root zone temperatures, which decreases dissolved oxygen (DO) levels. Rapid plant growth, combined with low DO levels, can cause oxygen deprivation which in turn can result in infection by opportunistic pathogens such as pythium.

    The key to maximum growth is to keep the air temperature at 75-80F, but the root zone at 68F or less. Note: the reservoir should be kept slightly cooler than the rootzone - irrigation and system heating will warm the water by the time it reaches the roots.

    Optimum root growth occurs at 70-75F; however, destructive root diseases also grow and reproduce rapidly at these root temperatures. Maintaining nutrient temperatures at or under 68F maximizes root growth and DO, and inhibits pythium.

    Reservoir cooling options:

    Warm summer temps often require aggressive cooling measures. Bubblers and dwc are difficult systems to temperature regulate due to their (usually) small volumes and lack of external reservoir.

    Note: spray / drip / mist / circulate nutrients on a frequent basis to equalize reservoir and root zone temperatures. Intermittent spraying may require a slightly lower tank temp, to compensate for system heating occurring during "off" spray cycle. (ie. Keep tank temp around 64F for intermittent spray cycles, 68F for continuous spraying).

    Note: submersible pumps add heat. Use an external/inline pump to minimize heat transfer. High quality digital thermometers are recommended.
    • Add cold water when topping up.
      Note: abrupt changes in temperature may shock roots.
    • Frozen pop bottles/milk jugs.
      Fill to ¾. Keep extras in the freezer to replace thawed bottles with new frozen ones, replace as necessary. Note: "Freezy packs" tend to crack and leak.
    • Increase size of reservoir
      Larger volumes are slower to warm up, pH/ppm is more stable and tank changes are less frequent.
    • Put reservoir/bubbling buckets onto floor, or set on concrete blocks to conduct heat away from the water.
    • Insulate
      Paint all exposed system surfaces white or use reflective material (such as mylar or reflectix). Wrap insulation around tank. Use a camping cooler for a reservoir (pre-insulated and comes with a drain!).
    • Swamp cooler
      Blow a fan directly across the surface of reservoir for excellent evaporative cooling. This method works well (expect a 10F drop in res. temp), but humidity and tds will increase, and more frequent topping up will be required.

      [SIZE=-2]430 scrog[/SIZE] "?add a computer fan to a duct blowing into your tank (cut air exit holes). You can run it on a timer (1 hr on, 1 hr off). I run a float valve to keep it topped up."
      Make sure lid and reservoir can be easily removed.
    • Blow air through the root zone
      Divert small amounts of cool intake air directly into the root zone.
    • Remote reservoir
      In-room reservoirs will quickly heat up to room temp. Put the reservoir (and ballasts) outside of the grow room to minimize tank heating.
    • Airstone / Power head / Venturi air supply should be drawn from a cool source (ie. Cool outside air).
    • Peltier coil (Thermoelectric chillers).
      [SIZE=-2](Bayou grower)[/SIZE] "I use an Ice Probe ($125) and it works well. It uses 50 watts and pulls the temp down 4 degrees under ambient. Cools 10 gal or less." (see for more models)
    • Reservoir chillers
      These are electric A/C units made specifically for cooling water. (Search for "Aquarium chillers")
      [SIZE=-2](smokin fl)[/SIZE] "?a heavy box with fan and compressor coils, with a 5 foot refrigeration line with a titanium coil at the end. All you do is plug it in, set the controller and put the coil in the res. Circulate nutes for the best cooling. Get a bigger model than you need."
    • Cooling coil
    [​IMG] A coil of stainless steel is put into the reservoir, cold tap water is trickled through the coil and the overflow runs down the drain. A circulation pump in thte rez makes the cooling more efficient. Adjust tap flow as necessary (Water use can reasonable). No power, unlimited cooling, quiet.

    Making your own cooling coil:

    Scrap yards and appliance repair shops are full of A/C and fridge coils: 4-20 loops (more surface area is better), with male garden hose connectors welded to each end (Don't use copper or nickel coils). Available in Hydro stores (around $100 cdn).

    Note: Cooling coils may not be useful for those on metered water.

    DIY heat exchangers: try hot tub suppliers, home brew stores.

    stucklikechuck Well-Known Member

    awesome thread! i have a built in resevoir under my table. what is the best way to chill the res? should i just put frozen water bottles on the table and let the bottles cool the water while having a fan blow on top of the table? my current water temp is 77 degrees and i am a little worried. will this shock the roots? thanks!

    GypsyBush Well-Known Member

    How cool is too cool???

    Say... water at 58F to 62F... root zone at 66F to 68F.... plants at 70F to 72F...

    Is it just slowing growth? or are there other detriments?


    Guilt Active Member

    Good aquarium chillers are $400+ ... there is a better solution.

    Craigslist :) Go on craigslist, find a water cooler... you know the ones you put jugs in, push the button, and you get water to drink ....

    I see them for under $30 all the time. Rip it apart, and make use of the coils =)
    Aeroman14 likes this.

    mrbuzzsaw Well-Known Member

    i have been pulling my hair out trying to find a good way to diy a cooling unit
    i think i have finally found a cheap way to do it. i will test it out and let ya all know what i come up with
    Stay tuned!

    Guilt Active Member

    Let us know how it turns out!

    TengokuCannabis Well-Known Member

    Anyone using a ebb & flow system have any problems with water temp rising?

    Bullethead21 Well-Known Member

    What about converting a PC water cooling kit? I have already used PC fans that I pulled off these mini radiators that the water passes through and get cooled by the radiator and the fan attached to the radiator. Its all a 12 volt DC system and very easy to convert both the fan and water pump which could be mounted right on the side of the outside of the tank....a couple of 12v DC adapters for power to fan and pump and your all set.

    It should circulated the water from inside the tank through the cooling resevoir and bump back in cold water into the tank.

    Just thinking aloud here...I just remember how easy it was to convert a 4 1/2 inch PC cooling fan mounted on the back of a PC cooling radiator for the PC cooling unit and splicing to power to 12v DC adapter I had layng around and then using that for a exhust fan. All else needed was a 10 foot piece of dryer hose to make the exhaust vent.
    GypsyBush likes this.

    Bullethead21 Well-Known Member

    Well so far the plans are looking good. One can actually do this without drilling any holes in the tank which is no big deal for the tubing for the inlet side. The outlet side after water has been run through cooling radiator can also be layed over top with the power power to the submeged pump or you could drill another small hole at the top of the tank somewhere for your return water thats nice and chilly......

    Only obstacle I ran into so far is matching up the tubing and fitting size. Seems I got 2 or 3 different type PC water cooling kits around and they all dont use the same size tubing. SO once I get some more cheap tubing I should be all set. This is all gonna be mounted externally either directly mounted on the outside of the tank, or a nearby shelf will work nicely also.

    Ill ppost some pics after I get the tubing I need.

    BTW- just in case any are interested, Im using parts prom a thermaltech and Bigwater PC water cooling kits. The fan on the radiator is 4.5 inch fan size...standard 12v DC.....I can give you more specs if you have specific questions.

    Bullethead21 Well-Known Member

    Could someone explain in detail how you would go about running a fan to blow air across the water thats inside the tank? In one of these post that was suggested as a way to keep res temps down...just wondering exactly how that would work....

    Thank You!

    GypsyBush Well-Known Member

    That was me...

    And by the way... SUPER PROPS FOR THE PC CHILLER!!!! YOU ARE THE MAN:clap::clap::clap:

    I kept a big ass fan, like a house fan... in front of my babies... and as soon as I noticed the the temps climbing, I would crack open the lid to the res.... allowing the fan's wind to blow across the water..

    Very crude, but it worked by about 10F at least...

    Please take pictures and do a DIY post on this chiller you are working on...

    I know several people here that would greatly benefit...

    Thanks a million.... and +rep all the way Bro....

    mjg132 Active Member

    The trouble with the pc water cooler setup is the rad ,being brass/copper adding 'nasties' to your nutes,another is the reliabilty of the 12v pump, especially on timers.
    The best 'delta-t' you could achieve is 4*C above ambient,remember,the pump you use will be a source of heat.

    Bullethead21 Well-Known Member

    Very true mjg132, but A- we are talking very small amounts of heat, very small, and B- dont really care that its a small heat source because in either instalation its NOT inside the tank like a submersed water pump is, so the heat is NOT warming the water in your tank.

    mjg132 Active Member

    Yes it will heat the water,the pump has water flowing through it and therefore will heat the water ,its part of the 'bottleneck'.

    Bullethead21 Well-Known Member

    I over clock CPU's all the time and heat is our main factor to deal with. I assure there would be no heat genertated by this pump, plus, thats wat the radiator is for silly, to chill the water so what goes back into the tank in nice chilled water.

    ANd the raditor I use which I will picture later will not get anthything nasty that will harm your tank, not if you use good equipment anyhow. I dont want anything nasty in my cpu cooling system going through my very expensive bigwater tank and res., everything is very clean and filtered.

    Here is a small pic of a demo test run Im about to do just to see what the temp coming out will be like...the radiator is not pictured here but will be in the bext one after I get the tubing installed correctly.

    AS you can see first off the type of pump is made to be mounted inside a PC case so its tested not to put off any heat to heat up the inside of your PC case, Ive tested it, it puts off vertually no heat at all, pluse its a external mount and not even touching the tank, its about 8 inches away at where the pump is currently mounted. This is just one of many ways to mount the pump and radiator....

    Attached Files:


    mjg132 Active Member

    I understand PC watercooling too,i have it,and im not being silly. :)
    Yes the rad/fans will cool the water,but during that process the elements that combine together that produce heat are part of the equation,an equilibrium is achieved whereas the hot begins to cool and the cool becomes the hot,what's left is the compromise and the final temp. You wont get lower than at least 4*C above room temp.

    justsmoking Active Member

    Yes I'm using the ebb n grow system and need a chiiler if you keep it under your HID :-)

    GranolaGumbo Member

    I live in a very warm and humid climate and I tried to do hydro in an outdoor shed. I tried everthing from simple fan systems to a complicated homemade water cooler circulation setup.
    I'd suggest saving your pennies and getting a real water cooling unit for your res. I think you'll end up at the same conclusion, but it should be fun to watch.

    Good Luck!

    CDXX Active Member

    For my dwc res with 15 gallons of water, I use the CoolWorks Ice Probe. It works VERY well, Chills the water to 10 degrees below the air temp (the air is about 80, and the water is just under 70). It is cheap, efficient, and easy to install. I was able to augment the unit's cooling ability to taking an additional clip fan, and pointing it at the heat sync. This additional airflow helps the unti chill more effectively. I'm planning on insulating my tub, and that should further increase the chilling effect. Here are some pictures:
    iceprobe2.jpg iceprobe1.jpg
    Dr.funkenstien likes this.

    fatman7574 New Member

    Some good info here but the thread starter began the thread out with lots of bad info that pretty much makes almost all the other information moot. A properly set up and run system does not need cool reservoir temperatures so as to have reservoir water with a higher DO. Nutrients are actually taken up better at warmer temps about equal to the plants temperature. Plants roots really do not need a lot of DO, so the temp is not an issue. The issue is large masses of roots suspended in water (DWC) or laying thick in the bottom of a tube or a through can not get access to enough water with DO as most water never comes into contact with the center of the large root masses in ost sysytems. Indreasing staurated oxygen by lowering the ten mps still dies nor bring the root masses center roots into contact with more water so the whole issue of temps and higher DO therefore is entirely moot. The difference in bacterial growth between 68 degrees F and 90 degrees F is pretty negligible. Build and operate better systems and quit thinking lower temps and higher DO is the answer to bacterial problems such as root rot. It is not the naswer. syatems such as samll y tube aeros, NTF am nd poorly circulated DWC with too many plants can easily develop root ri ot even with low temps and g high DO. Poor designs and poor operation is the problem not reservoir temp and reservoir DO. If the DO all around a root mass is high but the DO of the water in the center of the root mass is zero or near to zero there will be root rot. Lowering the temp and thereby possibly raisng the DO around the rooyts does not mean the center of the root mass receives any more watercirculation than before so it wil still have zero or near to zero DO water there, so root rot will develop. This hold true for DWC, NTF, and small tube aero systems.

    Simple as that. Yes there are things that can be done to help those systems but no one asked for that information they just wasted time talking about needlessly lowering reservoir water temps. Go figure.
    bgmike8 likes this.

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