In an Aquaponics grow bed the water from the fish tank that has just flooded the bed is drained and returned to the fish tank by the Bell Siphon Valve. This valve is integral to the flood and drain system. In this brief article I am going to attempt to describe the components and the workings of this valve. It is worthy to note that although you can purchase these valves online, they are simple and much cheaper to build yourself and I might ad, fun to do!

There Are 4 Main Components To A Bell Siphon Valve:

• Drain Hole
• Stand Pipe
• Bell Cover
• Media Guard

The drain hole is placed in the bottom of the grow bed so the water from the fish tank that has flooded the bed can pass through the bottom and return to the fish tank. This can be made several ways but has to be able to receive the stand pipe or maybe a better way to say it is the stand pipe needs to "plug in" to the drain hole. Common sizes for drain holes are 3/4 to 1 inch and are made with PVC fittings or a bulk head fitting.

The stand pipe is plugged in to the drain hole fitting and is cut to the proper length so the water level in the grow bed is about 1 inch under the media surface. So if a grow bed is 12 inches deep (the most common depth used) the stand pipe is cut so the flood level is between 10 and 11 inches. Once the flood level is reached the fish water is drained back to the fish tank.

The bell covers the stand pipe all the way to the bottom of the grow bed. It is several inches taller than the stand pipe so there is a sealed air space above the stand pipe when it is in place. The bell is made of PVC or similar material and is a larger diameter than the stand pipe. When in place this allows not only an air space above the stand pipe but also completely around it all the way to the bottom. If the stand pipe is 3/4 or 1 inch in diameter then the bell will need to be 2 or 3 inches in diameter. A piece of pipe of this diameter cut the same length as the stand pipe or a little longer with a cap installed on the top creates the "bell" that covers the stand pipe. At the bottom of the bell tube you will need to cut notches or drill holes all the way around at 1 inch high or less. These will allow the siphon effect to break and the bed will refill for the next cycle.

The media guard is just a large open ended tube with holes or slits cut into the sides. This allows the water to flood around the bell but keeps the media (gravel or other substrate) clear of the valve. If your bell is 2 or 3 inches in diameter then the rock guard will need to be at least 4 or 6 inches in diameter and will need to be a little taller than the depth of the grow bed.

These 4 components make up the Aquaponics bell siphon valve. If done correctly they should drain your bed in at least half the time than it takes the bed to flood. This cycle should be repeated at least several times per hour. Four times per hour seems to be the most common although some set up their systems to cycle faster than that. Mine cycles at three and my plants do well. For me a written description of the bell siphon valve is hard to visualize, images or video is much better.