RDWC UC - How many cycles per hour?

I was trying to figure out what size water pump I need for my 4-bucket RDWC undercurrent setup.

It'll hold 70 gallons and will have a separate pump for the wort chiller. There will only be about a 12" rise to account for.

Someone gave me a formula and I just wanted to confirm these numbers because the systems I've been researching have shown much smaller pumps for the same amount of water.

Formula: Gallons x 12 = gph needed

For my 70 gallon system, this would equate to 864 gph required, which means I would get a danner 950. That seems large. Other setups this size were using 500gph pumps.

Does "12" represent the number of complete re-circulations per hour? If so, is that number correct?

I'll have valves in place to control flow, but I was curious about the effects of having too much flow, or too little flow.

So are you growing weed or brewing beer(wort chiller)?

When growing plants, the whole objective of the "cycles" is to get oxygen into the water. From everything I read, cannabis needs a LOT of air in the water. The normal one gallon exchange per hour on the attached sheet for aquaculture/aquaponics is NOT enough.

The "12" is someones rule of thumb for cycles per hour... probably high to account for weed's crazy need of O2.

Too much flow is unlikely. Too little flow will result in rotted roots... cannabis roots need lots of oxygen.

You should have your buckets in series, not parallel... this way you don't need valves to control the flow... and all your plants get max flow.

There are several ways to get air into water:
1. Circulating the water. (This is what you are talking about).
2. Bubble air into the water with an air pump.
3. Design waterfalls into your system. Falling water has been shown to be the most economical way to add air to water. You could put a mushroom fountain head on your pump as a way to achieve this. (http://www.amazon.com/PonicsPump-FHS4-Fountain-Patterns-Mushroom/dp/B006M6MSAG). A PP40006 would likely be a big enough pump.
4. En-train air with a small axial flow pump. I could teach you how to build one in a private discussion if interested. Total watts used would be much less.

Full disclosure, I am the owner of PonicsPumps... so while I know a lot about pumps... I am also biased.

Ron

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WeedBulbs said:

So are you growing weed or brewing beer(wort chiller)?

When growing plants, the whole objective of the "cycles" is to get oxygen into the water. From everything I read, cannabis needs a LOT of air in the water. The normal one gallon exchange per hour on the attached sheet for aquaculture/aquaponics is NOT enough.

The "12" is someones rule of thumb for cycles per hour... probably high to account for weed's crazy need of O2.

Too much flow is unlikely. Too little flow will result in rotted roots... cannabis roots need lots of oxygen.

You should have your buckets in series, not parallel... this way you don't need valves to control the flow... and all your plants get max flow.

There are several ways to get air into water:
1. Circulating the water. (This is what you are talking about).
2. Bubble air into the water with an air pump.
3. Design waterfalls into your system. Falling water has been shown to be the most economical way to add air to water. You could put a mushroom fountain head on your pump as a way to achieve this. (http://www.amazon.com/PonicsPump-FHS4-Fountain-Patterns-Mushroom/dp/B006M6MSAG). A PP40006 would likely be a big enough pump.
4. En-train air with a small axial flow pump. I could teach you how to build one in a private discussion if interested. Total watts used would be much less.

Full disclosure, I am the owner of PonicsPumps... so while I know a lot about pumps... I am also biased.

Ron

Click to expand...

Hey Ron, I really appreciate the advice. I've got experience with hydro/aero, esp RDWC. But this will be my 1st undercurrent.

I was trying to get the specifics about the flow and aeration as to not go too little or waste money. I've gotten mixed answers on some of this stuff.

So, I'll be running 4x13-gallon square hydro buckets with a 35 gallon reservoir.
The manifold will be 2"
Reservoir/controller will be on a chiller with a wort coil. No, not brewing lol Running a closed-loop chiller on a small pump instead of running nutes through it on the main line.
I was planning on using the airforce AP80 and grey-cylinder air-stones
For the inline water pump I was looking to either use an EG Danner 700, or a 950. This is what I'm trying to nail down

Because I'll be using a 4x4 tent, I'll be running the buckets in parallel.

It'll be modeled after this, but with my own mods:

I was reading about how it's possible to over-aerate roots with bubbles from an air pump. That's why I was wondering about too much flow. Didn't know if there was some negative effect associated with that.

So now, do I just want to go with the minimum required pump (I'd say the Danner 950) or step is up to the 1200 because even more flow is better?

Please give me links on where you are buying your air pump, hydro bucket and reservoir, etc.
I will do my best to help.