The ebb and flow method of hydroponic gardening works by flooding the grow bed over an extended period of time, then quickly draining all the water. You can hook up a timer to the water pump to turn it on and off in intervals or run the pump continuously and set up an automatic siphon to drain the grow bed once the water level reaches the desired height.
Here are 3 different types of automatic siphons you can use to automatically drain your ebb and flow hydroponic system.
The Bell Siphon
Many hydroponic gardeners use bell siphons to automatically drain their ebb and flow systems. It’s one of the more complex automatic siphons and consists of multiple parts.
To set up a bell siphon, first, a bulkhead fitting is typically placed at the bottom of the grow bed and has a standpipe connected where the water will drain. The standpipe length allows the water level to reach a few inches below the top of the grow medium, then starts flowing down the standpipe and drains back into the reservoir.
Over the top of the standpipe is the bell. The bell has holes or slots at the bottom allowing the water to rise inside the bell and down the standpipe. A larger piece of pipe with small holes or slits is then placed around the bell. This acts as a filter to keep grow medium from being sucked down the drain.
When the water spills over enough the standpipe enough to fill it, a vacuum is created in the bell, and water from your grow bed is sucked down the standpipe. When almost all the water is drained and air enters the bell into the standpipe the vacuum is broken, allowing the grow bed to fill again.
The Loop Siphon
A loop siphon is one of the most simplistic automatic siphons used to drain an ebb and flow hydroponic system. With a loop siphon, a PVC hose is connected to the bottom of the grow bed that is looped on the outside of the system. As the water in your grow bed rises, it rises in the loop as well.
When the water level comes over the crest loop enough to fill the entire hose, a vacuum is created, sucking the water from the grow bed. When the grow bed drains enough to allow air in the tube the vacuum breaks, allowing the grow bed to fill again.
The “U” Siphon
A U siphon has some characteristics of both the bell siphon and loop siphon. The U siphon setup usually consists of a PVC pipe drain that is brought up to where you want the water level to be, then brought back down to your reservoir. The shape the drain makes is similar to an upside-down U and can be rounded or squared at the top.
As the water rises in your grow bed, the water in the drain pipe rises as well, eventually flowing over the crest of the U. When there’s enough water to completely fill the drain pipe, it creates a vacuum and the water is sucked from the grow bed into the reservoir. As with the other siphons, when enough air gets into the drain the vacuum breaks.