RDWC success - without a chiller

Hey all. I’m curious to know about those of you that have built/ran RDWC setups and did not have a water chiller, yet were still able to have successful grows.

Also, what arrangements did you make to keep your reservoir water temperatures cool in lieu of having a chiller? The idea of throwing in frozen water bottles seems like a pain but if I must I must.

I am in the final stages of building a one site (yes, it’s a little ridiculous) RDWC system, and apart from having the res outside my tent, I will be using insulation around my one container and painting it white.

This is a basement grow where the ambient temp is ~67F in the summer (I live in the “north”). Thanks in advance!

Sounds like you don't need a chiller.

Get good led lights and a dc pump and put your sites on the floor and you'd likely be fine without one with that low of an ambient temp as long as you have a large enough water volume. The more water you have the easier it is to keep under control.
Maybe insulate the sites and lids a bit if you want to go the extra mile.

When I used to do RDWC and DWC I poked a 1/4 inch hole in my wall to the outside and ran an aquarium line from the air pump to the outside using a DIY filter I made out of a old vitamin plastic bottle that the line ran into stuffed with cotton. I did this starting in October until April and used the frigid cold air to cool down the reservoir. It got so cold that I had to use an aquarium heater to keep it at 68 degrees and it worked perfect.

fragileassassin said:

Get good led lights and a dc pump and put your sites on the floor and you'd likely be fine without one with that low of an ambient temp as long as you have a large enough water volume. The more water you have the easier it is to keep under control.
Maybe insulate the sites and lids a bit if you want to go the extra mile.

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Thanks for the suggestions. I decided to go ahead and use some reflective insulation for the grow sites, as well as paint my tops white. Much appreciated!

DarthVaper84 said:

Thanks for the suggestions. I decided to go ahead and use some reflective insulation for the grow sites, as well as paint my tops white. Much appreciated!

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Oh and, I already had an LED because I figured HPS/MH would be crazy hot. I’ll lost some pictures of the whole setup soon

twistedwords said:

When I used to do RDWC and DWC I poked a 1/4 inch hole in my wall to the outside and ran an aquarium line from the air pump to the outside using a DIY filter I made out of a old vitamin plastic bottle that the line ran into stuffed with cotton. I did this starting in October until April and used the frigid cold air to cool down the reservoir. It got so cold that I had to use an aquarium heater to keep it at 68 degrees and it worked perfect.

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Could you elaborate a bit more on exactly how you pulled this off. I’m definitely intrigued

You can get a successful RDWC grow without chillers, it's just more difficult to avoid pathogens. In my opinion, definitely go sterile if you choose the no chiller option and push a fair amount of air through micro pore diffusers to ensure adequate DO levels.

DarthVaper84 said:

Could you elaborate a bit more on exactly how you pulled this off. I’m definitely intrigued

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Sure

Simple plan:

Drill 1/4 inch hole into your wall to the exterior of your residence.

Buy 1/4 inch drip line from your hardware store. Black drip line is important as it keeps out the light and is excellent for hiding.

Get a old pill or vitamin bottle (8 oz) or so not too big and stuff it with cotton as the cotton acts as a filter so when it pulls air from the outside it captures any dust or dirt. Drill two 1/4 inch hole in the top and bottom of the bottle. The 1/4 inch drip line in the bottle will be cut one for intake and for out.

Place an exterior Aquarium pump to the reservoir with the 1/4 inch drip line. It is best to use exterior pumps in case they fail you can tell as you will either hear them working or not and easily replaced on the outside of your reservoir. Plus the heat they generate is far less on the outside.

On the intake of the pump connect the 1/4 inch drip line to the bottle you made on the bottom. On the top of the bottle run the 1/4 inch drip line through the hole you made to the outside of your residence. Leave it dangling on the outside of your house with a good length but not on the ground. It will look like a old coax cable for hiding purposes.

added bonus on top of above if you do RDWC instead of using the pump for the air agitation get a venturi as this combines oxygen with water and agitates at he same time. Only use the above too cool.

Thank you for the detailed explanation! Do you have a model recommendation that has an intake line? Most of the ones I’ve seen have what you might call an “internal inlet” and then just an outlet

If you’re going over 72-75F you really are asking for problems. I’ve pulled off 78-80F before but it’s really not a proper practice.

Most people will tell you to add beneficial microbes like Hydroguard. I did this for years but it doesn’t guarantee you won’t get root rot.

The best thing to do would be to run a sterile environment using a product like UC Roots ( or attempt to make your own bleach solution).

The real issue is that even if you can avoid root rot, higher water temperatures cause lower availability of dissolved oxygen.

Wow I was unaware of this product. Just read about it and it seems like a great addition. Any downside to running something like this during the grow?

Also, I have a bunch of Gen Hydro FloraKleen that I was planning to use during change outs. I wonder if that would do the trick as well...

DarthVaper84 said:

Wow I was unaware of this product. Just read about it and it seems like a great addition. Any downside to running something like this during the grow?

Also, I have a bunch of Gen Hydro FloraKleen that I was planning to use during change outs. I wonder if that would do the trick as well...

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The downside is it's pretty expensive. Many people say its like $50/gallon for bleach water but it certainly works. Just keep in mind if you've been adding beneficial bacteria, adding UC Roots will also kill that bacteria. I'm having much more success going completely sterile.

DarthVaper84 said:

Wow I was unaware of this product. Just read about it and it seems like a great addition. Any downside to running something like this during the grow?

Also, I have a bunch of Gen Hydro FloraKleen that I was planning to use during change outs. I wonder if that would do the trick as well...

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If you are in the US, get Southern AG garden friendly fungicide. Its the same thing as hydroguard but 1,000,000 times stronger so it works way better and is considerably cheaper. They cost about the same per quart but you can dose 1ml per 5-10 gallons instead of 3ml per gallon of hydroguard.
Most of us using beneficial bacteria around here are using the southern ag.

And no the florakleen isn't going to do much to help with anything.

Don't put bleach in your system plz. If you want to go sterile use h2o2 or pool shock for chlorine. If you want to use beneficials use southern ag.
Either choice will keep you good up to about 75F water temps.
Much above 75F and there's not really anything that you can put in there thatll work 100%, that's the danger zone.

This is a great suggestion. I’m really hoping I won’t approach 75F, but I’ll determine that based on testing the system with full water and no plant tomorrow. Looks like I may very well go with the non-sterile route using beneficial bacteria.

@DarthVaper84
Fragile's suggestions are good.
Use cold floor to advantage, keep an eye on water temps - might need aquarium heater.
Use a DC water pump (less heat, etc)
If you need something for "sterilizing", you can also make hypochlorous acid with salt and water and some electricity - youtube that if you want.
Use reflectix or similar on tops (and sides if you want) of planter, use rigid insulation if you want.

Good luck.

Thanks all for the great advice. I did my first “dry run” (kind of a misnomer...) tonight with my LED light at full power and my 20 gallons of water running through the system for the first time. After a couple hours my res temp was 69F (started at ~68F) and I believe this is close to the max it will achieve.

I painted the lis of my grow site matte white and wrapped the 8-gallon pot (probably overkill) in 1/8 inch adhesive insulation. Picture of grow site and res attached. Basically the same bucket except the res is a 12 gallon and taller. Same lid.

Things look pretty good from what I see.
70F is fine, I keep my chiller set to 68F to try to keep my systems 68-70F.
Looks like you've given yourself a decent enough shot here.

DarthVaper84 said:

Thank you for the detailed explanation! Do you have a model recommendation that has an intake line? Most of the ones I’ve seen have what you might call an “internal inlet” and then just an outlet

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If I am understanding your question correctly I have used the EcoPlus 396 GPH and it comes with the Venturi attachment. I believe the pump is 20 dollars at any hardware store.

I run RDWC and no chiller. My water temps range 72-76 depending on time of day. I brew up some beneficial bacteria tea and add it 1cup per 5gal and it keeps the rot/slime/algae away. No issues.