Backyard Aquaponics
A place to discuss aquaponics

I'm having problems getting my bell siphons to start reliably. I have 3 4'x4' (1.3 x 1.3 meters) grow beds with a 1" bulkead fitting and 1" standpipe, 2" siphon tube and 3" media guards. The water is rising higher than the standpipe and I dont get any flow until I manually lift the siphon tube. Once I lift the tube I quickly get a siphon and if I lower it back down very slowly it will maintain siphon. I'm thinking the cause for this is that as water rise within the grow bed and siphon tube, a pocket of pressurize air builds inside the siphon tube and prevents the water from reaching the standpipe. BTW I am running a U style trap on the bottom of the bulkhead to prevent air flowing backwards, this could well be why that air pocket is building up inside my siphon tube.

Have any of you ever encountered this problem? Is there a simpler solution to using a check valve?

Thanks

Why?...

Remove the "U style trap" and you will no longer have an airlock.

The return line from the bottom of the siphon standpipe back to the FT/ST should run slightly downhill, have no ups & downs that can create air-locks, and the discharge end into the FT/ST should not be under water. You want to avoid airlocks.

I find the optimum design for the return line is a short vertical drop of a few inches underneath the standpipe, in the same diameter pipe as the standpipe. Then a 90 degree elbow. Followed by about 15cm (6") of horizontal pipe of the same diameter.

If the horizontal section of the return line needs to be more than about a metre (3ft) long, then it should empty into a larger diameter, non-airtight return line that runs slightly downhill back to the FT/ST.

I find that for the initial part of the horizontal return line, ie: the part immediately after the elbow and that is still the same dia as the standpipe, that 10cm (4") to 30cm (12") is the ideal length range, with about 15cm (6") giving optimum performance.

Definitely poor drainage. I am only using 20mm stem but with 50mm bell and 100mm media guard (so I can get my hands in) I ran two lengths off 25mm pipes sitting on the IBC frames with an 90deg bend and a piece of 25mm pipe pushed up against the bottom of the tank tight into the 90deg bend held in place by the 1.3 metre pipe going down to a series of sep downs. But both my pipes are submerged in the sump tank! I put a small hole in each pipe and added a 4mm flexible hose as a venturi. So I add extra air to my water and allow the bell to break better. Getting the bell to break siphon can also be adjusted by the water inflow.

If you use a glass jar as your bell with a bit of plastic pipe with the slots in it taped to the jar opening, you can see whats going on and figure out ways to fix it. beats the hell out of using a plastic bell with no window. its actualy interesting to see what realy goes on.