Water Feedline

I came across this set up and would like to know what the black venturi tube does? The water is going from left to right. The tubing going off to right in the photo goes onto feed through the watersoftner and iron remover.

Would I be correct that this venturi has something to do with iron removal?

The little spigot on the bottom side of the venturi appears to be an air addmitance valve?

Assistance appreciated.

Raymond Wand
Alton, ON


sorry not a clue. maybe a back preasure valve to work with the shut off valve above for servicing the filter?

Is that a small tube coming out of the Venturi?

If so, it's obviously not being fed through the water softener. Maybe this particular water doesn't require treatment and goes to an outside spigot.

I think the idea of the venturi is to allow air to be sucked in through the spigot. Air entrained in the incoming water assists with percipitation of iron out of the water?

Raymond Wand
Alton, ON