Backyard Aquaponics
A place to discuss aquaponics

with the 65mm pipe, the weight keeps it down on the pillars, I had the water over 50mm (2") above the pipe and it just stayed there.

The water flow rate is a deciding factor, if the water doesn't rise quick enough up to the top of the end cap then the spillage of water through the gaps on the drain pipe is not overcome and you get false starts in that it will start to siphon but doesn't gather enough pace before air is sucked in via the air tube and goes the wrong way.

Other factors also contribute to the siphon being sluggish, I connected my 2nd grow bed on the weekend and had about 800mm of pipe from the grow bed to the fish tank - and it was almost horizontal aaaah!

Raised the bed about 50mm and all worked fine - will have it documented shortly

Pump flow rates into the grow bed, I had it down to 400lph and it was working fine with the large size drain pipe.

Les

Hey Ell;

I know this thread is two years old, but could you put up what Figure 4 would have been? I understand everything but the 3mm air hose.

I've been staring at the bell siphon pic at http://www.tiwalkme.org/BellAndSiphon.htm for a long time, and I still don't get it. =(

Your designs are the coolest things ever. I am almost certainly going to use the Gates of 'Ell when I get that far! =)

Hi Swanberg, check out the Les Thread on Autosyphjons here http://backyardaquaponics.com/forum/viewtopic.php?t=685

2 years old and mine is still working well

Karen, the link you have supplied is the same principle. If you look at "the improved Bell & Siphon" diagram at the bottom of your link...they have a "tube" which is also used as an air intake when the siphon action is complete.

Somehow, we inverted it and got the siphon to work in aquaponics - the "tube" is used to suck in air at the end of the drain cycle to fill the siphon chamber with air and stop it from getting into a balanced state where water entering the dam/GB is flowing out at the same rate

What works conceptually for me is to think of the water as one of those toy trains, where the cars are joined together by magnets. The siphon works by the train going up a hill, and there being enough intertia for the front of the train to pull the back of the train over the hill. The small air tube is like a device for breaking apart the magnets when the train is moving too slow, to separate the front from the back. The front of the train is then free to move along down the hill without being connected to the back. The back then is free to fall behind until it gets its own mass of cars behind it to push it up the hill.

Excellent explanation DD. It is sometimes difficult to understand the principle of a syphon - you make easy/simple.
heka

hi EllKayBee

great siphon pages - very informative

It took me a while but I understand how this works now except for one thing, can you tell me the beginning and end point of the air tube and the route it takes. It would be much appreciated. thanks

Hi WH and welcome to the forum...here is a pic of one dismantled:

The inner pipe represents the drain pipe, the end cap to the outer bell housing is next to the main pipe, the holes in it were experiments to see if it made any difference where the air tube was placed ( not much really...and those holes have been re-sealed)

the top of the air tube is just below the end cap when it is placed on the bell housing (it is not critical)

The bottom of the air tube is about 50mm (~2") above the crenellations - again this is not critical. it could still work if it was half way down the length of the housing

Try not to go less than 50mm from the base so that the water doesn't rush up and cover it when the siphon action stops...air entering the air tube won't stop the siphon working (it just acts like a venturi sucking in and mixing with the water)...it is when the siphon stalls by a big gulp of air is drawn under the bell housing/crenelation gaps that the air tube comes into play filling the bell housing with air.

hope this helps and looking forward to seeing your own system thread and pics as your system progress

I put my air tube out the top of the cap

I put mine out the side and saved more than 50mm in 3mm air tubing

(working on the current AUD/USD currency exchange rate that works out to more than 0.001 cents rounded : D )

Yours is prettier

Great thankyou

I understand now, I was confused by your other pic of the air hose going out of the tank and into the outlet pipe outside (underneath) the tank - but I see its principly the same thing.

I am still scouting and doing cost research for my set up but when I do get it set up I will definately bring pics.

thanks again

Yeah, that works well too but the cost of air tube was exorbitant

...the long air tube that did 3 laps of the GB was one of the first experiments which then got modified WH

heya

I have a couple of extra questions

Is the u-bend in the outlet to make sure the water isnt just spilling over the siphon pipe and not activating the siphon action? ie. I cant just have a straight outlet pipe coming out from under the GB?

And the dimensions you give for the outlet pipe fromt he bottom of the GB is 250mm. Does this create a flood level of 25mm? my question relates to how far below the gravel height flood should occur. Ive read 2-3cm, so if I have a 29cm bed with gravel heigh at 28cm my outlet piping should rise to 25-26cm from the bottom of the gb?

I just want to be doubly sure of these, thankyou for any help.

Chad

hi Chad,
Yes, the U-bend is to stop the water from just running out...with a large diameter pipe it is easy for the water to just overflow down the stand pipe and not rise above far enough to start the siphon action

The measurement of the length of the drain pipe should be:

the height of the gravel depth
minus 2 to 3cm (this is the amount below the GB media to keep dry)
minus 1 to 1.5cm (the water will rise about this height above the drain pipe before the siphon kicks in)

so drain pipe height should be 3 - 4 cm below gravel height...make the height less and then it can be cut down if required

So yes, your figures are pretty spot on