[RE-wrenches] Well siphon?

[Windy Dankoff]

William,

The drop from the wellhead at 1200 feet, down to the tank at 800 ft. will, if full of water, create a strong suction with the potential for siphoning water out of the well. But, as Darryl says, the limit of water lift by suction is roughly 30 feet. So, assuming the water level in the well is more than 30 ft. below ground, it will not siphon.

Once the water is being pushed up by the well pump, the siphon effect will kick in and assist the flow, reducing the power draw of the pump. How much? Only to the equivalent of 30 ft. if the downward pipe is full of water. A pipe size that is adequate but relatively small, will help keep the pipe full of water, and allow it to siphon-assist (somewhat, and hard to predict).  Regardless, the gravity assist it is limited to a 30 ft. advantage -- not much if the water level is way down in the 300 ft. well.

The main advantage of the suction, as I see it, would be to allow you to use a minimally small pipe size going down the hill. Gravity will compensate for friction losses. 

It took me a couple decades to wrap my mind around this. I'm glad you asked  :-)

Windy Dankoff
Co-Author, upcoming book – "The Solar Water Pumping Handbook"