Pond Boss Forums AERATION Should I aerate? Securing a 20' Windmill on Gravel/Sand

Rowly - Welcome back. Let's see if we can straighten this out for you. You better print this out and study this because it gets a little detailed.
1. A. Wind & pressure. Despite what you may have read/heard from others or from 'some' advertising your mill will not produce 1 cfm or greater until the wind speed gets 24mph to 31mph(pretty stiff wind). I have the wind speed/cfm flow charts to prove it. At slower wind speeds the air flow (cfm) is proportionally less. The mill will generate bubbles in as little as 5mph but only a few bubbles compared to those produced in a 20mph wind. So air flow volume (bubbling action) is dependant on wind speed, as you will notice during operation at various wind speeds.

B. You talk about "waste of energy... as pressure increases with strong winds". This is going to test my ability to explain with written words. I may need to get wordy to get the point across. As explained above, air volume will increase with wind speed but the maximum pressure produced will be about the same at medium and high speed. You can prove this if you want. Put a pressure guage in line or if you have a freeze control tank, it has a mounted guage. Now, block the air flow and watch the guage at medium vs high speed. All wind speeds above 10 psi can produce close to 30 psi. Maximum psi produced or recommended by the company is 30 psi. DO NOT let pressure build higher than this. Mechanical damage will start to occur at weakest parts above 30psi.

Maximum depth of your diffuser will determine the minimal psi & minimal wind speed necessary to produce bubbles. Shallower the diffuser the less pressure needed to release bubbles. In a VERY gentle wind notice how the fan will spin forward several turns and then spin backward. There is not enough wind speed to continue to develop enough compression or pressure to overcome the pressure needed to release bubbles; thus the build up of internal hose & bumper tank pressure pushes back on the diaphragm and causes the fan to spin backward. Again this only happens in very gentle wind. But it demonstrates that wind speed sometimes is not enough to overcome the pressure needed to release bubbles due to water head presssure. The deeper the diffuser the higher the head pressure and higher the minimal wind speed needed before a diffuser will bubble.

So actually there is never no wasted pressure. The mill can in moderate to heavy wind generate ample pressure but psi (pressure) will only build up enough to get the bubbles releasing and then pressure will not increase beyond that point UNLESS there isan airline restriction. The only thing that will increase with greater wind speed is the air flow volume (cfm). There is no pressure tank with regulator to allow pressure buildup beyond what is needed to release bubbles.

2. Two bubblers simultaneously. The mill does not generate enough air flow most of the time to adequately run two bublers at the same time, unless you don't expect very many bubbles from each bubbler. IT Could be done but water movement would be minimal from running two at once. You will be dividing what little air is produced between two diffusers. The more air volume each gets the more bubbles that will be produced. Try it and see if you are happy. Measure effectiveness of circulation with a water temperature profile study in the vicinity of each bubbler.

3. Two bubbers at different depths. I'm not sure how well this will work with the mill so I will explain operational theory with an electric air compressor and you apply it to your mill. I have never done this with a mill because of the reasons in #2 above. Minimally, to get both bubblers to work each at different depths you need a ball valve in line for the SHALLOWEST bubbler. With the compressor in operation, and the valve closed keep opening the ball valve until both diffusers produce bubbles. What you are doing is restricting or regulaing the airflow to the path of least resistance until the operational pressure to both diffusers is the same. Air will always want to go to the shallowest bubbler or path of least resistance. The ball valve equalizes them out. I do not prefer this method because it will not work very good as the bubblers start to plug up or become clogged. Now this method becomes pretty useless since the bubblers are causing variations in pressure between the two bubblers.

Best way to operate both bubblers is with a ball valve on each airline. Now you adjust airflow to each by adjusting each ballvalve. Keep in mind that all the air wants to go to the shallowest bubbler. With two, I leave the deepest one wide open and close the shallowest bubbler, then I open the valve on the shallow diffuser until I get the desired flow in both. As the bubblers clog over time you may need to redjust the valves. It's best to clean the bubblers and their attached check valves annually.