Not at all. Several DWC recirculating designs actually use only an airpump to circulate the water by actually injecting all the air in the line at the system low point (end of the circuit) hose via a tee and relying on the air bubbles to carry the water up-ward to the the system above and poured into the high point res (the beginning of the circuit).

Air solubility is limited and only a minute amount dissolved into the water, which is just enough for plants needs, so you can beat the heck out of the water and it won't matter unless you start agitating the actual roots.

Whether a lot of air going into your pump will lessen its lifespan is another good question for someone with more experience, it would be interesting to take apart a mag drive pump and see how vulnerable it looks.

Not at all. Several DWC recirculating designs actually use only an airpump to circulate the water by actually injecting all the air in the line at the system low point (end of the circuit) hose via a tee and relying on the air bubbles to carry the water up-ward to the the system above and poured into the high point res (the beginning of the circuit).

Air solubility is limited and only a minute amount dissolved into the water, which is just enough for plants needs, so you can beat the heck out of the water and it won't matter unless you start agitating the actual roots.

Whether a lot of air going into your pump will lessen its lifespan is another good question for someone with more experience, it would be interesting to take apart a mag drive pump and see how vulnerable it looks.

What Pupilla described is refered to, at least here, as an air lift. apparently they use the system of lift in waste water treatment plants. If you're so inclined, you can search this forum for it, and find a few decent discussions on it.

Several years back I made an on-board live bait tank (Shad), for one of my boats. It utilizes something similar. the pump is mounted below the boat's water line and is therefore self priming. 1/8" ID aquarium tubing is epoxied to the inlet side of the pump via a short piece of 1/8 OD brass tube. The 1/8 clear tubing then goes up to a needle valve salvaged from an old Cox .049 model airplane engine, introducing a controlled amount of air to the inlet side of the pump. It is awesome. The water in the tank takes on a milky cloudy appearance and the surface of it sizzles and hisses like a freshly opened bottle of club soda. It lowers the pump amperage draw, just don't open the air valve too much or the pump will cavitate and go through momentary glitches of air lock.
I'm sure there is a limit as to how much air can be mixed into H2O before it cooks off (evaporates), just as their is a limit as to how much H2O can be suspended in air before it condenses, (as in ultrasonic fog type systems.)
Both methods seem to work quite well when applied to many types of plant's root zones in hydroponic gardening.
~Ken~

Liquid pumps don't like to pump air (cavitate) and you can hear cavitation.

Use a throttling valve to control cavitation.

Needle valves throttle, plug valves throttle, ball valves throttle.

I have been using Home & Garden A&B Flake and they do not recommend using air stones. Since my roots all are really long now i have taken out my little water dams and allow the bigger root balls to slow the water flow and it seems to be working. I have not been using the air stores for about 6 weeks and everything looks good except for my Zucchini plants. They were huge and producing and i dumped a bunch of rain water in before i left for two days and did not adjust the PH. I thought having the high PH was the reason i developed the powder mildew on the leaves. But am wondering if not having the air stone in and around their huge root system was the problem. Thoughts

Thoughts:

When I looked at your rig, my thought was that there was limited or no opening for fresh air to circulate. Between trying to keep things clean and heat in winter, I figured you had it under control. I don't think the pH is going to influence much what grows on the leaves, btw. Sounds like too much dew or humidity.

It is not clear what you mean by "they do not recommend using air stones". Whether it is they recommend not to,, or simply have nothing to say about it.

In any case, you don't need an airstone, but you will appreciate it in a few weeks more after for sure your roots start getting a Pythium fungus or some root rot mold in that setup and low oxygen inner conditions. A fertilizer is a general product, and we all need to tweak it, they obviously didn't make it with your particular consecutive design in mind which is especially vulnerable to oxygen depletion. Not to get me wrong, I like your rig a lot, just to clarify they all have benefits and drawbacks to deal with.

You need to be proactive and introduce air before it gets out of control - airstone, reasonable open points for the entry of fresh air, or crashing down return water instead of gently having it settle with something to allow air flow -- corvette shark gill flaps if you get fancy and want t keep out light, or many other possibilities.

This post was edited by PupillaCharites on Sun, Dec 8, 13 at 13:14

Thanks for the info. Hear is how i have my water returning to my reservoir. My only question is would i have enough O2 left for the last plants.

I need to do some reading and changing of my Hoop House. I have vents but i do have a lot of moisture. I am using it just for temp use with the (2) 28 degree nights and 5+"s of rain down pours.

I don't remember how long your plant path was, but it was probably around 32 feet. In the beginning that is no problem, nor is it a problem if the plants are small rooted. As a matter of fact some people go 100 feet on straight nft channels. Therein is the devil in the detail.

You don't have an NFT setup strictly speaking. It is a hybrid NFT/RDWC. This is because the pipe bottoms are rounded, so there is no nutrient film thin layer for that technique strictly - and that is how the oxygenation stay high for so long.

Yours on the other hand varies from NFT in that as soon as your roots get massive, the structure of your channel is to leave oxygen deprived roots at the pipe low point. You may have a liter or two per minute returning, but it says nothing as to how much water is retained by all kinds of damming from root matting and balling. Inside that zone is where the O2 depletion occurs with this design, so it is what I'm thinking about.

Can't exactly get my bearings from the picture, but what I'm assuming for typing sake is that it is the underside of the lid of the res which has a PVC drain coming in and ending in a shower drilled out standard end cap. There is no scale, but I would consider blocking out the center large hole since you might get more overall bang for the buck if the fall is relatively non-violent if everything was forced to exit through the radial perforations instead of possibly all going though the center due to gravity, centering, and water tension in the thick cap. I am making a return right now and I think I'm going to figure out how to use one of these temporary caps instead of the expensive big ones. They are cheaply made, thin, but flat which will distribute the shower equally. Easy to perforate and might have an advantage as my thinking goes over your cap - experiment time. Not saying this will solve the over all drawback, just saying that every little bit helps.

O2 depletion = root rot, even if the plant gets sufficient O2 from the upper root zone. Hope this helps.