Backyard Aquaponics
A place to discuss aquaponics

I'm hoping this is an easy fix. I just set up my first system (55 gal upright blue barrel, another barrel cut in thirds width-wise, no I'm not using the center ring, and a 30 gal flooded raft.) Plumbed using 3/4" pvc (and 1/2" hose from the 400 gph pump, split 4 ways). I'm using an afnan siphon (3/4" to 1" standpipe with a 2" pvc bell with a cap without a tube). One of them is working perfectly. The other won't completely break the siphon. It'll drain loudly, almost stops but then starts trickling a steady stream, and, when the GB is half full, starts siphoning again.

I tried removing the 1" top, using just a 3/4" standpipe...same thing. I made the cuts on the bottom of the bell bigger...still the same. I discovered next time I'll use a 4" media guard because, while I can get my hand in the 3", it's NOT comfortable (no way could my husband do that). What am I missing? Why is one going so well and the other being such a booger? I spent my entire weekend waiting for water to siphon!

General rule - wont start, not enough water... wont stop, too much water..
Does your outlet have an elbow? Is it going into a pipe or straight to fishtank?

Hello. I agree with above. My was not stoping and slow my flow and solved the problem.

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It has a 90 degree elbow going to an 18" straight pipe (the FT is slightly more than a foot away).

Thanks for the advice! I didn't realize this. (Spent so much time thinking about every other thing, this detail must have slipped me.) I'll work on slowing the flow into this one today. See if that works. (I foresee more staring at water running/not running in my near future...) If this doesn't work, I'm going to change it all over into a timed system and just stop messing with this aspect of it. (Now to look up how to make a timed system since it's still too dark to stare at water flowing/not flowing...)

Freya

I'm giving up and going with a timed system. Is there some link or explanation of what size and where to drill the hole on the pipe? Thanks!

Just drill a 1/4 inch hole at the base of the standpipe tube

Perfect! Thank you.
I have my timer and I'm fairly good with a drill. Tomorrow it starts.

Freya

Just for anyone else reading this, apart from what others have said, another reason a siphon doesn't stop can be that the water that dumps out of the bell can raise the level locally within the media guard, and restart the siphon.

The solution is to allow greater flow through the media guard, or sometimes it can be to reduce the size of the bell.

Remember the flow that matters is the flow at the bottom of the media guard. The holes at the top don't do anything when it's stopping time for the siphon.

So plenty of holes in the media guard down low, and no excessive amount of water in the bell (ie dont make the bell too big or too high. twice the diameter of the standpipe is good, and a bit higher than the width of the standpipe.)

And good luck with the system Freya!

Good point Bull

In those rare instances when my affnan won't stop, I reduce flow.

Just an update.

I'd switched both growbeds over to a timed flood and drain (30 on 30 off during the day, 30 on 60 off during the night) and it seems to be working perfectly! The system is nearly cycled (no ammonia, an excess of nitrites, I think, and a good amount of nitrates.) All the plants have started growing fast. I've 5 happy little goldfish (still. I had 6, one died. I think it was aggression rather than environment that did him in, though.)

So, I'm really liking the timed system. Thanks for the advice! (I'll try the siphon on another system.)

If I may...I built my first system today and everything worked beautifully right up to the bell siphon. It started draining great, but then topped at the same level as the top of the stand pipe. My stand pipe is 1" my bell cover is 2" and I'm about 3" differnce from the top of the stand pipe to the bell pipe cap.

One thing I noticed, I used no 90 degree elbows under the system just a straight pipe to a 45 degree. Is that the probelm. Thank you guys so much in advance. I am going to be thinking about this all night until I can solve it tomorrow!!

If you can increase the flow rate to your grow bed and that should help it get started.
If you can't or it doesn't help, if you put a 1.5" to 1" reducer on the top of your standpipe that should fix it (google affnan siphon)