Backyard Aquaponics
A place to discuss aquaponics

Just wondering if anyone has a simple design for a loop syphon (with an overflow in place) which I can copy from. Photos with labels would be great!

I don't know if its because I'm a physics pleb or anything but I am having trouble with the concept.

I didn't believe they would really work either till I started tinkering myself.

Let me see if I can find a picture to link for you. There is a whole thread for siphons but I don't remember if it included loop siphons or just bell siphons.

Have a look at froggos thread - he has a good pitcure of one in his new growbed. Last page.

On the end bucket on the right is a black tube that is hooked to a "drain hole" on the bucket and curves up to just a little below the top of the bucket and then back down to drain into the bin below the buckets. That is a loop siphon. Scary how little there is to it huh?

Loop siphons are wonderful when you understand and get them going... Getting them going initially can be tough.
There are some problems involved.

First up, how they work.
When off, the system is as in figure 1
then as the water increases in volume, figure 2 happens.
then if the inflow is high enough, figure 3 can be seen.
It is at this point you need your outflow to be much higher than your inflow. So make the outlet pipe as short as possible.
If you have a long output pipe, then the outflow is slowed by resistance, and if you're unlucky, airlocks as seen in figure 5
the other problems that can occur, are that the system stabilises in figure 2, ie the inflow matches the outflow without the pipe ever filling fully.
If all goes well, the water level will drop, and then the siphon will suck air, as in figure 4, and stop, until the water level rises again
Another problem that can occur, is that when the tank is empty, and the siphon sucks some air, the inflow again matches the outflow, because the outflow is reduced by the airlock. as seen in figure 6.

I have found all these problem to be fixed by having the drain VERY short. (Mine empties into a larger pipe, which returns it to my sump)

I hope this helps, and doesn't scare you too much. They are perfectly reliable once you get them working. So tweak away :-)

Yes +1 on the mention of having the loop drain into larger pipe just by sticking the end in the pipe.

Good pictures there kuda

a suggestion on which I would like your comments:
to avoid air locks, wouldn't it be better to
1. have a 90° elbow at the top of the loop so that oce over the top the water falls straight down??
2. submerge the exit of the loop ?

frank

I've sometimes had problems in situations where the exit of the loop is submerged (granted, this is usually in situations where I don't have enough elevation to work with) it would sometimes stop the siphon from starting fully by trapping an air bubble in the top, or in other situations keep it from stopping by not letting air in at the bottom. There are ways in which these "issues" can be made to work in one's favor though.

1. Water as I have found so far HATES corners with a passion. To encourage good flow, bends should be used in preference to elbows. Also elbows are a fitting, and therefore have rough uneven bots after fitting, and cause extra resistance and swirling of current. I have found (using horribly underpowered pumps) that I can get much better flow to my growbeds by reducing the elbows, and just bending the pvc pipe to my will.
The best loop siphon is in fact a loop. I have tried square 'loop' siphons, using elbows, but the looped flexi pipe is clearly the best I have found.
Your idea for a vertical exit however is spot on, the end of the loop siphon should be straight up and down to encourage the siphon to start nicely.

2.I have found that submerging the end can cause nasty airlocks, as the siphon is designed to suck air regularly, there is no way to prevent these... of course if it's free flowing and a short length, airlocks are unlikely

Wow... thanks for that help!The diagrams make more sense to me. I'm a little worried about the air lock thing. If you manage to get it working, does that mean the air lock problem is solved or is it likely to become an issue at some stage?

I'm thinking I might have a little go at making a tiny version today at work (school) and see if the students can explain it to me... they usually can!

Get your students (and yourself) to setup a simple stepped auto-siphon system.... like Simmo's...

viewtopic.php?f=8&t=470

It'll amaze them... and teach them the principles....

Hmmmseem to have missed that topic, yeah I agree, very good example of autosiphons. Hands on is always a good approach... I seem to only draw things I'm never going to build, or have already built :-)

I kept getting kinks in the pipe so I cheated and used elbows.

Say Duff do the siphons work any better differently using the elbows?

Have not had a problem yet. I even used a small bit of plastic tube inside the second elbow to help the water back up to get the siphon going quicker. Only time will tell.
What I have found is you get the same siphon on every drum because you can make sure the different parts are the same size.