I recently set up a small EZ-Flo fertigation system. This is a tank full of fertilizer solution that you attach to a pipe that you are using for a sprinkler or irrigation. As water flows down the pipe, small amounts of fertilizer are "injected" into the water from the tank. This is a passive process entirely driven by the pressure from the water source.
There is an adjustable valve in the pipe at the site at which it attaches to the tank. There are branches in the pipe on either side of this valve. These are an input to (before the valve) and output from (after the valve) the tank. Both the input and the output are thin, flexible hoses that connect to the tank, where they become dip tubes that travel to the bottom of the tank.
When the system is working, as water flows down the pipe, some of it is diverted down the input into the tank, where it mixes with fertilizer. Simultaneously, fertilizer solution is siphoned up the output, where it joins the pipe on the other side of the flow restrictor.
The above EZ-Flo link is a simple illustrative video of how the system functions. Mine is basically like the one shown, with the exception that the fertilizer tank is about 1 foot under the pipe.
I have observed that, if the pipe's valve is too open (i.e. not restricting flow), then no fertilizer seems to be injected-- there doesn't seem to be any outflow from the tank. It is hard to tell exactly what is happening, but the (transparent) outflow tube remains clear. When the valve is further closed, the outflow tube fills with the (colored) fertilizer solution, indicating that it is being siphoned up into the pipe. So it seems 1 of 3 things is happening when the valve is too open:
- The clear pipe water flows down to fill both the input and the output, rather than water flowing down the input and fertilizer up the output.
- Air remains in the output tube and the pipe water flows over it.
- Somehow a very diluted form of the fertilizer (so diluted it looks clear) is taken up the output. But I don't know how this would possibly occur, since the input water has to travel through the fertilizer solution.
Can someone explain what is happening?