Backyard Aquaponics
A place to discuss aquaponics

I know siphons require some site specific fine tuning, but I am interested in getting a general idea of the necessary height to achieve a reliable siphon starting and ending.


How much effect does the diameter of piping have on siphon starting?
Is there a diameter too large for auto siphoning to be successful?
If the height difference is not great enough, will auto siphoning fail?

I'm considering pipe diameters of 3"-4" and flow rates around 3,000 gph

First: Do you NEED siphons?

Pipe diameter will dictate how much water can be moved that pipe, (almost) without regard to whether it's in a siphon or not. Flow rates have a much larger impact on the siphon design, not enough flow (into a pipe too large) and the siphon wont start and insufficient flow (into a siphon too small) and the siphon wont stop.

You don't have to design the total flow (unless you've only got one MASSIVE GB?!): What is the flow into each GB in which you will install a siphon.

There are a million syphon threads Stonewall, do some reading mate because the answers are out there.

That's the problem- there are so many of them with so much info to sift through. I've read a lot of them and gained some good knowledge



The flow rate would be c. 3,000 gph (<1m/s but depending on pipe diameter) on average, but I have not estimated an instantaneous flow rate when the siphon would be active.
I don't NEED siphons, but I like the idea. Maybe more of a headache than it's worth?
I am considering stacking one GB above another so just a corner (potential siphon location) overlaps. I'm trying to make considerations for the heights of all tanks/GBs to see how high I may need to start out or if it's even feasible.
I've read elsewhere that a flow rate below 1m/s is proper for pipe sizing.
Is there a golden number for flow rate of auto siphons?

At what rate is water going to be flowing into each growbed? How big are these growbeds?


KISS. If it doesn't NEED them, then don't add them! Don't add complexity where it's not necessary.

This doesn't solve the flow rate question though!


Huh?


1m/sec is exceptionally fast for water in an AP system. Add a decimal point in there and start working with velocities more like 0.1m/sec. Where did you read 1m/sec?

http://www.backyardaquaponics.com/forum/viewtopic.php?f=11&t=22673&p=470811#p470811

If you really want to know how fast water has to be moving to keep waste solids in suspension, there are formulae you can use, or you can simply time how long it takes for a particle to sink a known distance in a bucket of still water. Do this for several sizes and densities of waste material and take the fastest value.


You can play with Bernoulli's principle and equations if you really want to, there is no "golden number".

I love the siphon on my systems. I've seen the BYAP trials, and saw that they had pretty similar growth rates, but I can't help but think the siphon has an advantage over the others.

It drains out dead spots, so parts of the bed where water might not flow as well (water will take the path of least resistance, so I think the water will mostly move in a straight line from the inlet to the outlet, and not go into the edges/lower areas of the beds). I also think you'll get better aeration from the siphon. So the rushing water will create more oxygen, and when the wet media is exposed to the open air, it'll take in the oxygen, which doesn't happen with constant flood beds.

And they aren't that hard to setup. It looks difficult, but you twist the ball valve on the bottom, and watch it, make another adjustment, and it's reliable and works without thought.

The most interesting thing I found about the BYAP trials, was the worms in each bed. The F&D beds had considerably more worms in there, which I view as a good thing.

For the sizing, I just used the same size pipe as the inlet pipe (40mm in my case), and double that for the bell over the top. Works like a charm.

EDIT...

And it's still awesome watching them kick on and off. So much water moving so quickly.

There are times and designs when siphons may be necessary; a continuous flow system may be one such example.

Siphons should be carefully designed: if they were "that simple" there wouldn't be hundreds (thousands?) of posts on this forum regarding siphon troubles. Even when a siphon is installed, their sizing should be faithful to the principle that water is filtered "better" when it moves slowly through the filtration media, and the flow through a siphon should be carefully "matched" with the flow into the GB, not only for starting and stopping the siphon action, but to ensure an appropriate cycle time.

I'm pretty sure the solids cling to the biofilm/media when it passes through, so I doubt the water rushing away wouldn't be filtered as well. Plus I think the water being sent to every corner of the GB, and drained from every corner of the GB will provide more filtration, and give the bacteria more time to convert the ammonia.

For every 1 person asking for help, there is 100 that got it working without a problem. I'm not saying it's not fullproof, you need to follow a few guidelines, making sure the elbow is pointing down, and getting the flow right. But once it's all setup, it will work reliably.

They really aren't that tricky.

.
+1 on EVERYTHING Colum said... ESPECIALLY the part about for every 1 person that can't get them working there's probably 100 that have siphons running successfully.

I've been selling siphon kits for years, I've lost count of how many I've sold... and until a few days ago I'd only had two people that had purchased siphon kits from me call me back because they couldn't get them working. In both those cases it was simply a matter of adjusting the GB in-flow rate and their problem was solved. In this recent third case, the customer hadn't fitted the elbow and short length of horizontal pipe underneath the siphon, once they did the siphon worked flawlessly.

Of all the situations on forums where someone has been having ongoing dramas with their siphons, in almost every one the siphon design has been the problem... usually over-designed. It's not rocket science, they are aren't difficult, they aren't complicated... in fact the simpler the design the better...

Which brings me to the aforementioned K.I.S.S. principle... you can't get any simpler and any more reliable than a well designed, built, and maintained auto siphon... there are no moving parts, no timers to fail, no small drain holes to block up, and no stopping or starting of the pump.

Contrary to what the Youtube siphon gurus will tell you... Siphons DO NOT NEED breather tubes, breather tube cups, inverted reducers atop the standpipes, or any other widgets, thingamyjiggers, or attachments... Keep the design simple!...

- The bell should be 2-3x the diameter of the standpipe.
- The bell should have sufficient holes/slots near its base to enable full flow for the diameter of standpipe.
- The holes/slots in the bell should be near the base, but not at the base, so about 1-2" of water remains in the GB.
- The outer gravel guard should have PLENTY of slots or holes cut/drilled into it.
- There should be a short length of vertical pipe immediately under the siphon.
- At the bottom of the vertical pipe there should be a 90º elbow with a minimum 6" length of horizontal pipe.
- For a single siphon the horizontal should run slightly downhill and be no more than 1m in length.
- For longer single horizontals, or if running multiple siphons, they should empty into a larger Ø, non-airtight return line.
- The GB in-flow should be tuned once the gravel is in the GB.

Also... A siphoned F&D system can EASILY be swapped between siphoned F&D and Constant Flood... in a matter of seconds... by simply removing/replacing the bell... So you get the benefit of two different operating methods, if required, ie: keeping the GB's flooded on cold winter nights etc.

I have done my system a little different than on most of the clips, due to my situation having brought 19mm bulkheads, I am only using two IBCs here but, with experimental running I have found a few faults with the norms of syphons! Most use a screw on fitting To the bulkhead? I use a loose slip fitting allowing extra air in the syphons, my drainage overflow pipes are sunk into my sump tank below the water line, with experiments I have found, approximately 25mm to 1 inch gap between the stand pipe and bell works best, I am using 20mm stand pipe 50mm bell 100mm outer cover, 30mm drain pipes, one for each grow bed 1.2mtrs long!
I am not sure off you GB size, but you could use two syphons in the one bed if you build them identical, and have an even inflow into your grow bed, like a fully surround piping around the GB! With two drainage pipes, at 3000gph? You will be better off with 90mm drainage pipes and a really big sump tank!

Only one siphon will ever initiate.

This is all good stuff, especially the pro tip about the ball valve for fine tuning!

I think I'll have to digest this info and come up with an elevation plan and floor layout.

Ball valves are a bonus, I have five fitted, all the screw in type! Their not cheep but the screw in fittings are? And so is thread tape,

Colum nailed it. There are for sure plenty of ways to skin a cat, but FWIW my siphon works 100% and is an integral part of what makes my system as nerdy and enjoyable as it is. I use my system in part for education and an autosiphon is one of those "how in the world does THAT work" things I love explaining. While some portion of users will certainly have to tune and troubleshoot, I think it's likely a robust minority compared to the total of them out there. It just works, works well and consistently, and is cool if that matters .