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Bell siphon problems...in our classroom aquaponics system

Hello..my students have just set up an aquaponics system. It's been cycling for about two weeks, yesterday they planted a couple of starter plants, and added red wigglers to the mix.  Today, they added more water to the aquarium. The siphon was working well until the water was added. Though the discharge pipe is about 5 inches above the water level in the aquarium, and the water pumped into the grow bed remained the same; the siphon stopped working properly about three hours after the water was added.  Now, the siphon doesn't stop unless the bell is pulled up to break the siphon. FYI our bell design, there are four little teeth about 1/2 high at the bottom.  thoughts of why it's happening... thank you so much.

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Sounds to me like you have faster inflow to the growbed because of the higher water level in the aquarium. When the inflow is high enough to equal or surpass the minimal speed with which the bell can maintain the siphon, they'll reach equilibrium and the siphon won't break.

Increase the flow rate from the siphon--sounds like you can increase the size of the holes at the base, which might be what's limiting your flow rate right now.

My $0.02.

Thanks Jeffrey,  I'll talk with my students tomorrow about redesigning the base of the bell. I appreciate hearing your 2 cents worth.. :) 

Jeffrey Ihara said:

Sounds to me like you have faster inflow to the growbed because of the higher water level in the aquarium. When the inflow is high enough to equal or surpass the minimal speed with which the bell can maintain the siphon, they'll reach equilibrium and the siphon won't break.

Increase the flow rate from the siphon--sounds like you can increase the size of the holes at the base, which might be what's limiting your flow rate right now.

My $0.02.

Hi Patricia,

You can put more "teeth" or increase the size of the existing ones. If the siphon is still not breaking, place 2 elbows(90 degree bends) on a 6 inch extension pipe and connect it to the end of the discharge pipe. One elbow goes into existing discharge pipe and the other drains into the aquarium.

Harold, thanks, and Jeffrey for your input - we'll check that out today. Solving this particular problem, as well as others that will emerge,are teachable moments that will boost the confidence of my students who struggle with social and emotional issues.

for a cleaner, easier, cheaper fix... try reducing the "tail pipe"... if your stand pipe is 3/4" reduce it to 1/2" below the growbeds, this does the same thing as putting the two elbows (Afnan's model)

i have a bell siphon how to on my page if you would like to view more details.

heres the link to the bell siphon how-to.. i must add that i have gone to advising folks not to use a siphon, just go with the ol timer, flood and drain.

 

http://community.theaquaponicsource.com/forum/topics/how-to-build-a...

Yeah, yeah Rob. We all know that you were attacked by a bell siphon as a child and now have deeply rooted internal trust issues with them :D Still haven't had any problems with mine yet. So I guess I'm becoming your bell siphon arch nemesis.

Patricia, instead of adjusting your bell siphon, you could just probably just lower your water's flow rate. The issue is that the water is coming in to fast and the water level won't go low enough to let air in and break the siphon.

Rob Nash said:

heres the link to the bell siphon how-to.. i must add that i have gone to advising folks not to use a siphon, just go with the ol timer, flood and drain.

 

http://community.theaquaponicsource.com/forum/topics/how-to-build-a...

Hi Rob, Thanks for the link. I did check it out. I noticed that you use a snorkel, on ours, there is no snorkel. Also our media guard is 1/4 wire mesh rather than pvc piping. I see you use a 120 gph pump, I think ours is a 140 gph. I'm wondering if the pump is too much for our 30 gallon tank. The water is pumped 3 feet up to the grow bed?  

Rob Nash said:

heres the link to the bell siphon how-to.. i must add that i have gone to advising folks not to use a siphon, just go with the ol timer, flood and drain.

 

http://community.theaquaponicsource.com/forum/topics/how-to-build-a...

Hi Patricia,

For a 30 gallon FT you need to pump a minimum of 30 gal per hour. If you want to keep this pump you can put a PVC tee(90 degree joint) with extension pipe connected to a ball valve which empties into the FT. This is called a bypass line. The ball valve regulates how much water you pump to the GB's by redirecting some back to the FT. You can have the extension pipe, which empties into FT drilled with tiny holes(1/8 to 3/16) to add extra aeration to the system. However a properly sized pump will effectively save you up to 1/4 the amount of electricity you'll be using here.

BTW,  no wonder you're having bell shut off problems @140 gph

Hi Harold,  good suggestion. Learn by doing...trial and error...it's a learning curve for all of us.  BTW- the bell siphon was working before we added additional water to the FT. Interestingly, when I apply pressure to the top of the bell, the siphon stops.

Hi Patricia,

I've had much problems initially with siphons as well. They work then stop working.......its better to address the flowrate problem now as it will return time and time again. The bypass should take care of the problem. Also, too frequent flood cycles poses problems for a range of plants. Leafy greens like these conditions whereas tomatoes rebel, a happy medium is where you aim at

You know, my system is only a few weeks old and I started out with bell siphons. They were fun to build and the physics of how they work are quite interesting. However, they fail. A lot. I'm sure that the bell siphons were useful as a classroom exercise but you might want to consider putting a timer on your pump to do the ebb & flow. You can buy the timers at IKEA or Home Depot cheaply. I now run my pumps 15 minutes on, 45-60 off, and I get the same effect for 1/4 the electricity.

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