1 out of 3 Earth Boxes overflows

[DuncF]

I have 3 earth boxes setup one seems to overflow in the evening.  I have shortened the Black tube that the water sensor and bell go down hoping that would bring the water up higher and close the diaphragm.  No real changes.
Should I clean the water pressure valve and diaphragm?
Any suggestions??

[gardendoc]

Don't shorten the AWS tube, it needs to be farther in the reservoir so more pressure builds on the diaphragm

[MCL]

I would check to see if the AWS sensor is working. Just use a glass of water. Should shut off when in water and turn on when held over the water.

Last year I had an earthbox that I thought was overflowing, but it was roots that had overgrown into the water reservoir and draped over the lip of the overflow hole. It was acting like a wick and made a surprising amount of water come out (steady stream).

[Texas.Micky]

Another possibility is that roots have gotten to the sensor at the bottom.

My mint roots separated the sensor from the valve clear plastic tube, and that made the valve stay on and drain my rain barrel.

Check that the roots of your plants in that one box haven't mingled with the sensor.