Backyard Aquaponics
A place to discuss aquaponics

Well, I found it amusing at least...

We've got landscapers in (building me a slab among other things, woot!) and one of them was interested in my little test system and asked about the siphons (among other things). I explained how they work, and why one triggers a lot more often than the other one, and it got me thinking... it's actually kinda interesting how differently they run!

I have two teeny growbeds. They are the same size, use the same media, and have the same design of siphon - same size/height standpipe, same size fittings, same size bell, you name it, everything that I used to think of as having a strong influence on how a siphon runs is as close to identical as I could make them.

The left bed takes just under six minutes to fill and a bit over a minute to empty - 7:10 total cycle.
The right bed takes thirteen and a half minutes to fill and two and a half minutes to empty - 16:10 total cycle.

Obviously the left bed is getting a lot faster water flow than the right one, but if I change the balance at all the left siphon won't start and the right one won't stop. The only difference between them is the drain piping under the beds; the left one has a 45 degree plumbing elbow and a little bit of straight pipe, and the right one has a 90 degree elbow hose clamp irrigation fitting.



Sooooo... yeah! If you want to change how your siphons behave, fiddling with their drains a bit might be more effective than messing with the standpipes etc.

Hi Mel,

Yep!... The one with the 45 degree elbow will require a much faster flow rate to get it operating, and will have a greatly reduced operating window (in regards to GB in-flow rate) than the one with the 90 degree elbow. This is why it's now common practice to put a 90 degree elbow followed by a few inches of horizontal pipe after siphons. The little bit of back pressure it creates helps get the siphon working. It greatly reduces the GB in-flow rate required and greatly increases the siphons operating window. It makes them much easier to "tune" and much more reliable.