Picture of Make a Bell Siphon
A bell siphon is used in ebb and flow aquaponics and hydroponics systems in order to regulate the flow of water.  In an ebb and flow (also known as flood and drain) system water is pumped into the grow bed.  At a specific point (usually 2 inches below the surface) the water drains via the bell siphon.  When the water reaches the bottom you will hear the classic gurgle indicating the end of the drain phase.  The process will then repeat itself over and over again.  The bell siphon is a such an important part of any ebb and flow system that getting it right is crucial.  In this instructable I'll show you how to make your own, and tweak it to your needs.
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Step 1: Parts and Tools

Picture of Parts and Tools

Here's what you will need to make your own bell siphon:


Gravel Guard

  • 1 - 3" PVC pipe (approximately 12" long)

Bell Dome

  • 1 - 2" PVC pipe (approximately 10" long)
  • 1 - 2" PVC cap

Bell Siphon

  • 1 - 3/4" PVC pipe (approximately 6" long)
  • 1 - 3/4" to 1 1/2" bell adapter

Grow Bed Connections

  • 1 - 3/4" Male adapter (thread to slip)
  • 1 - 3/4" Female adapter (thread to slip)
  • 2 - #18 o-rings

Drain Pipe

  • 2 - 3/4" PVC pipe 4" long
  • 2 - 3/4" 90o elbow


Step 2: Preparing the Dome and Guard

Picture of Preparing the Dome and Guard
I created a guide that you can use to make clean and equally spaced holes around the bottom of your gravel guard and bell dome.  First download the Bell Holes Guide Document and print it.  You will likely get an error message saying, "The margins of section 1 are outside the printable area of the page.  Do you want to continue?"  Click Yes.  Cut out the two guides, wrap each guide around the bottom of your PVC pipes (the 3" gravel guard, and the 2" Bell dome), and tape them in place.  Use the guide to drill holes around the bottom of each pipe.  Remove the guides and clean up any left over PVC dust or tags.
ernter4 months ago
great help. my inner tube was to high so the "bell" couldnt catch enough water for suction to set in properly. it just drained slowly.
your advice on a proper bell-size fixed that issue.

as you can see i have a little different approach, the $1 version with:
- piece of 1.5" pipe, lenght 6"
- cut off 33 cl plastic bottle (for the bell), 3" diameter, length 8.5"
- cut off 1.5l plastic bottle for the stone guard.

barry_dh1 year ago

Thank you for sharing this. Unfortunately I'm not able to download the Bell_Hole_Guides.doc, its says "Request forbidden by administrative rules."

Could you please email it to me,

Thanks a lot :)

This still seems to be the case