Backyard Aquaponics
A place to discuss aquaponics

Hi guys, I'm not sure if I fully understand how an auto siphon works. I have read all the posts here and have played with it at home.

Is this correct?: You need to start the auto siphon for the first time and then it will work on its own? or should it work on its own all the time?

The reason I ask is that on the first cycle the siphon does not work. If I get it started by pulling off the top "U" the it will go fine on its own after that.

Thanks!
HNB

Incorrect - it should self start as soon as your growbed fills up to just over the highest point on the siphon.

playing around with input flow rate to the growbed would help.

They are very good and reliable once set up properly.

hmmm weird then because it did not start on its own but once I forced it it worked nicely.

I had a very difficult time with my auto siphons and still haven't finished the project. I will watch this thread closely AGAIN....and in the meantime wishing you luck HN

Tell us what kind of auto-siphon you are using and post pictures of all your auto-siphon parts -- unassembled and assembled, if need be. I struggled for a long while and Les (EllKayBee) was able to trouble-shoot for me. You can actually follow my trials on my thread and see pictures of what didn't work, what sorta worked, and what finally did work. One of us should be able to figure it out.

My small siphons are running really well!

Will post some photos soon!

It's all in the flow as Johnnie says. I gave flow rates for 13 mm in another siphon thread wont be spending another day timing them.

Never used an airbreak etc, just flow.

I'll go out on limb here but ditching auto-syphons for a simple flood and slow drain system was the best thing I ever did. It never fails to cycle, it never overflows and it never leaks.

I was always concerned about having the auto-syphon correctly adjusted and worried about overflowing when they failed (which happened several times). A build-up of bio-film and/or root matter would require a re-adjustment or clean.

My system has cycled faultlessly for 4 weeks now without auto-syphons.

My 2c worth.
Derek (leaves forum to don flame proof suit)

However, the water drain rate of 770L looks a bit fast, that is more than 11L/minute gravity feed through a 1/2 inch hose.

Nova

Just went outside and syphoned a 2L jug in 20 seconds, that makes it 10L/minute, looks like the 770Lph is spot on.

EDIT: Doh, my maths is bad, 6L/min, or 360L/hour like John said.

Nova

fuzzy math? 60 seconds in a minute would make that 6L/min or 360Lph? Maybe or no.

Weight of water on top pushing water beneath out faster etc etc.

50 litre bed (roughly) in my example, not including gravel (scoria) in my example.

I did some figures on pipe sizes to flow rates *here*
- I only went down to 20mm, max flow rate was ~1,500lph, if you keep working down, the figures supplied by AA is about right, there is more info on auto siphons on that thread also

I do agree regards the point raised about build up of bio film the need for cleaning and consequent re-adjustment after cleaning in my system.

But I am using rather slow flows, pumps are either piddly little buggers or throttled right back and I use small growbeds so I doont want the system cycling every couple of seconds.

In a larger growbed setup, with faster flows, I think that the need for cleanup would probably be much less frequent.

My 2 cents but a good point raised there by Derek.

When I go to a larger system we will see what happens!

I think autosiphons will be fine.

I am using a small pump to where the flow is good but not too much into the beds. There are two siphon hoses with essentially the same diameter as the one pump hose. So a two siphon hose to one pump hose ratio is working well here anyway. It is just a loop like Simmo's and no other devices to help it break. There has to be some length of hose below the bottom of the growbed or it will not work (my theory is that the inertia of the water below the grow bed pulls the water up over the hump to keep things going). Whether this will run into problems when there are a lot of roots and biofilm - ?

I wouldn't try using siphons with a bed that fills very slowly either because it is a big bed or a very slow pump. The height change rate needs to be "fast enough", which means I am using multiple small containers for beds rather than one big one.