If there is no pump in the well, a string with a weight can be use to check the well depth. If you can hear the weight splash, it will also give you the static water level.
Many well depth gauges use two wires with a weight attached to the bottom. Dropping the weight to the bottom can tell you the depth of the well. The wires are usually attached to an ohm meter or “sounder” at the top. When the two wires touch water, the ohm meter moves or the “sounder” beeps and you can mark the depth to water.
Dropping a weighted string or well sounder with weighted wires into the well can be problematic when the pump is still in the well. The string or wires can get wrapped around the pipe or pump wires and get stuck in the well. For this reason strings and wire type well depth recorders should not be used when there is a pump in the well.
When checking a pumping water level the pump must be installed and running. So a well sounder or string should not be used.
A sonic water level meter is expensive, but works fairly well to test the water level while the pump is in the well. However, it doesn’t always give an accurate water level, especially when the pump is running. Many times when the pump is running the water will be falling from perforations above the pump. A sonic meter can pick up the point at which the water starts cascading down, which is not the actual water level.
The best way to detect an accurate pumping level or static water level it to use an air line down the well.
You can make a very accurate level gauge for about 30 bucks, if you install it at the same time the pump is installed. I use a length of ¼” poly tubing that is long enough to attach able the pump and will reach to the top of the well. The tubing is open ended at the pump, and has a tee with a Schrader valve and pressure gauge at the top. Adding a little air with a compressor at the top will blow all the water out of the tube. Then the reading on the pressure gauge will tell you how many feet of water are standing above the lower open end of the tube.
With the picture below you can see the gauge read 9 PSI. For every 2.31 feet of water standing above the bottom end of the tube, there is 1 PSI on the gauge. So with 9 PSI I have 9 X 2.31 which equals 20.79’ of water above my pump. When it pulls the water level down until the gauge shows 1 PSI, there is only 2.31’ of water above my pump. The air line method is very accurate as it is not affected by cascading or falling water.
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