Backyard Aquaponics
A place to discuss aquaponics

I set the grow bed too low, so the outlet pipe runs into the dwb below the water level. From what i've experienced, the bell syphon only works IF THERE IS AN AIR BREAK BETWEEN THE DOWN PIPE AND THE DWB.
For the moment, I have got around the situation running my pump on a timer(15 mins on, 15 mins off from 0600 till 2100).
Does anyone else run their pump/growbed only on a timer? I suspect some plants will not get water, and the level of water will not get much beyond the height of the outpipe in the grow bed.
Theoretical question; if i drill into the pipe linking the grow bed and dwb, so that when the bell syphon cycle has finished, when the grow bed is empty and the water is not flowing down, would an inserted tube allow air to be introduced , thus breaking the vacuum?

Yep if you are using a timer you don't need a siphon, simply drill 1/8" hole at the base of the outflow pipe in the growbed and when the pump is off that will let all the water drain out.

If you want to run the pump 24/7 is to drill a hole in the cap of your bell and put a tube in it running down the side to maybe 1-2" above the bottom of the growbed. That will introduce air when the water level gets near the bottom and break the siphon.

You can also do both things if you want to if you want the beds to drain anytime your pump is off.

You can also put a "Tee Piece" on the bottom of your grow bed outlet and run a "Air inlet" pipe out from under growbed and up the side to above water level when grow bed is full , so one way from tee runs water the other way allows air in once level has dropped .

This is often used when we need to run water under a pathway for example and the grow bed drain pipe stays full of water this will allow air into the line to help break siphon .

FWIW I had the outlet of a bell siphon submerged at the end of draining and the siphon still broke fine every time, not that i'm recommending it or anything though.