Backyard Aquaponics
A place to discuss aquaponics

Hi all, I'm newish to aquaponics but not new to thinking about things....... I've recently been relentlessly testing siphons as well as looking at and coming up with ideas for siphons.

One thing I've noticed about every person who has ever written anything or spoke about on YouTube about siphons is that NONE OF THEM has ever mentioned 'rise rate' ie the amount that the water rises per second or minute etc. To understand what I'm on about you have to imagine you set up your bell siphon in a bucket just to see if it works. Now you take your watering can and pour it into the bucket...... Low and behold your siphon works first time. Now imagine that same siphon in the bottom of a swimming pool. You pour in your watering can and........ NOTHING! This is because the 'rise rate' is so much less. The amount of water passing over the rim of the standpipe is not enough to block it and cause the air to be sucked down the pipe to cause the siphon. Now that leads me to the next thing that I see frequently that I also believe to be wrong and that is that by placing a 'flared' neck on the standpipe it induces a siphon more easily...... This can't be right, let's think about it. You have a standpipe which allows (for arguments sake) 10 litres per minute to pass and a 'rise rate' which corresponds to 'A' less than 10 litres/min and 'B' more than 10 litres/min. With 'A' the siphon will never start as the rise rate is always less than the outflow capability of the standpipe and with 'B' it would start easily every time as the rise rate is more than the capability of the standpipe. So how on earth would flaring the neck make any difference?

Once again I invite you to think about the swimming pool scenario. Take a 10 litre per minute standpipe and add a big as you like funnel. By poring water into the pool at equal to or less than 10 litres/min the siphon will never start. BUT poor it in at 11 litres per minute or more and the pipe will 'choke' and start the siphon. You DON'T get more water simply because the neck is bigger you only get more water by adding more water! Think about it, water coming in at 10 litres per minute won't block a pipe capable of handling 11 litres per minute even if you add a diamond encrusted solid gold wide neck flare to your standpipe!

So in brief all bell siphons should be measured against mm or cm rise rates in a standard IBC bed. Ie 'if your system rises between 2mm and 4mm per minute this bell siphon will work.... Any less than 2mm pm and it won't start and any more and it won't stop.

'U' SIPHON

Pros.... No moving parts, empties the bed quickly, works a dream with the correct 'rise rate'
Cons..... Needs a high 'rise rate' to initiate the siphon (see note about Venturi)

FLOAT SIPHON

Pros.... Great idea, floats to max fills then sinks.
Cons...... Moving parts which if aren't tight they leak and if they are tight they stick. Also it only drains to the height of the cup float!

HYBRID SIPHON

I came up with the idea of a float siphon but with a bell so that when it sinks it causes a siphon like a bell siphon and it drains to the level of the bell air intake not the cup level.....

Pros...... What a great idea and it drains to the low bell air intake level.
Cons...... Moving parts....... I had problems with the plastic pipes friction sticking and didn't want to grease them!

That leaves the industry standard.......

BELL SIPHON

By far and away the best after weeks of hoping to re invent the siphon. Forget gimmicks like tubes with cups just make sure you have the correct 'rise rate' for the size outflow pipe and by getting the pipe lengths within an acceptable tolerance and maybe adding an adjustable 90 degrees bend for back pressure you've cracked it.

Pros.... Once set up to suit the rise rate you almost never touch em again.
Cons.... They need a bit of fine adjusting to get perfect, that said not much more than any of the above.....


'U' SIPHON WITH VENTURI

(mentioned above) I saw a YouTube clip of a guy with a U bend siphon who had a hole drilled in the top of the U and a pipe leading from the hole to some high speed water flow insisting it 'sucked out the air' and initiated a siphon more easily. I admit I DIDNT try this one. I did try to put the pipe internally (a plastic tube) which started in the top of the u bend and went down into the water flow that passed over the U in the hope that as the water rose up it would flow over the U and down the outlet pipe causing a Venturi to suck out the air in the U and initiate a siphon but results were inconclusive. I'll go back to this as I'm not sure I exhausted all possibilities.

KE.....

Imagine a volume of water with a depth of 1 mtr and a width of 1 mtr flowing at a speed x. and a volume of water with a dept of 1 mtr and a width of 2 mtrs flowing at speed x. which one has a greater flow volume. Thats how flaring on top of siphon works. by flaring you increase the width. well the best way is to try. so have you tried both?
the one thing that concerns me is the flow adjusting parts which is done by closing the ball valve from pump to GB which is equal to chocking the pump which is equal to increase amperage and shorter pump life. I have posted about putting a ball valve instead on the siphon drain and make the siphon a bit bigger but someone said i wont work. I'm not convince so have to try it. I wonder if anyone here actually tried it.

My siphon will definitely include a flared top. and much as I wanted to do it already my accident related injury prevents me from doing so. And boy I'm terribly bored. I'm going to post my plan in case you or others want to try. If you do please report back maybe save my arse being a guinea pig. But first I will explain the theories.

you do witness a bathtub or sink drain. And maybe a water draining from a round bottle neck container. chances is that you remember the vortex and the air hole in the middle of it. This is the natural order of draining fluid a vortex and a whole in the middle. Now imagine that in the middle of the siphon. It will mess up the siphon. yes? Siphon involves a host of laws includes cohesion adhesion and vacuum. My plan aside from a flared top is to stick a rod in the middle of the siphon and hope that by virtue of adhesion it will prevent that vortex hole from forming and of course will aid in closing water flow and siphon forming.

anyone who try please report back.

Tuning the water flow to the grow bed without throttling back the flow from the pump.

Good Idea, thanks. You seem to have a fix for everything. But still its best not to bypass back. we are trying to circulate water. Well maybe if we add solids filter on that bypass then we make use of the energy expended.

There is nothing wrong with by-passing some of the flow back to the tank. As far as making good use of the energy expended, it's doing just that, it's providing aeration of the water.

For the sake of simplifying the message, that diagram was of the most basic of aquaponic system designs. There are many thousands of people around the globe running systems in exactly that configuration, very successfully, without any form of mechanical filtration on the by-passed water... Don't fall for the "Solids must removed or your fish will die!" mantra. If well designed, a system run in that configuration is perfectly fine. I've been running a display system in my shop in exactly that configuration for 5 years now... just to prove a point. The fish are healthy, the plants are healthy.

Don't get me wrong, there are definitely situations where mechanical filtration is good practice, ie: when running a DWC or NFT component in the system, or when growing on a commercial scale, but for the average backyarder it's simply not required if your system is designed well.

If you want to take a step further and provide the optimum nutrients for your plants and cleanest water for your fish, while running a by-pass such as that, and without adding a radial flow filter or swirl filter etc, then see the diagram below.

Hi Julianbu, Philippines wow one day I'll go there!

for the siphon test with flared neck yes I tried and tried again with two pipes set at the same length. One with a funnel (cut off plastic bottle neck) and a straight pipe.

As for the two different size containers both flowing the same speed (X as you call it) the larger container is twice the size of the smaller one so the 'rise rate' will be half that of the smaller container. This means that once the water reaches the standpipe level and starts to pour down the hole the larger container will only be taking half the amount down the hole that the smaller one takes every minute.

As for the speed of the water due to the flared neck. Think of it like this....... In order for your standpipe to start a siphon it needs a flow rate of X (for ease of explanation let's say 10l/min) if your flow rate is less (again let's say 9l/min) the water just flows over the lip and never starts a siphon. So now you add a flared neck and these nine litres run down the funnel at great speed....... But it's still only 9 litres and not enough to trigger a siphon.

But what about if you do X Y or Z with the bell or the standpipe or etc? I hear people ask. It makes the siphon start easier. YES it does but a siphon that starts its flow at 8litres per minute (just for example) after you have 'tuned it' to the best of its ability is not going to start at 7l/min if a flared neck is then added.

I imagine one day in the future when some company starts to manufacture bell siphons commercially there will be a standard measurement container size (ie 1m x1m by 30cm) and all siphons will have a height measurement and a min, max litres per min flow rate depending on the diameter of the standpipe. The rise rate will only need to be known if your container is bigger or smaller than the industry standard. If your container is of a strange shape for example then you just measure the rise rate and if it is the same then the siphon will start. AS LONG AS your strange shape container is approximately the same volume as a 1x1x 30cm container. (Too small and it would start and never stop and too big and it would never start)

Julianbu, I've been giving some thought to your 'rod in the centre' idea. Firstly please note I HAVENT TRIED THIS. but a rod or stick in the standpipe hole is effectively decreasing its surface area and should therefore aid in starting the siphon easier with the same flow. It is in fact the same thing as reducing the pipe size. It would also however make it more difficult to then break the siphon.

I've been doing more tests today. I have 2 GBs at just over 1m2 and 30cm deep, with siphons set up to 25cm depth. The siphons are set up the same with no flared tops, 20mm pipes and the pipes that go on the underside of the bed are 68cm long and run parallel to the underside of the GB. Each pipe has a 90 degree piece on the end of the long pipe.

One 90 degree piece was set level and the other slightly pointing up. The pointing up piece on the siphon made it 'fire' ie start the siphon on a regular time interval within 30seconds every 23 minutes. The other siphon just drained at the rate of the inflow. A quick adjustment and 'boom' it fired and it fired every time after that all day long also within a 30 second window.

I won't be doing further tests I'm very happy with how they both work now. if anyone needs more details just ask! KE

I'm not sure how to do drawings let alone post them..... Sorry, I'll try and explain...

The pipe is 68cm because I am able to attach it to a support more easily. It Couldn't possibly work any better than what it does so I've no need to change it.

This pipe is parallel to the base of the GB. Attached to the end of the pipe is a 90 degree bend. You can point it to the left or the right. Initially it's also parallel to the underside of the GB but then I give it a few degree twist to point SLIGHTLY upwards. As the water starts to flow into the pipe it reaches this slight upturn at the end and has to wait until the water level in the pipe is high enough to start to flow over the edge.

Once it flows over the edge it seems to stop and go back in the pipe then it flows over the edge again but with slightly more force and once again back in. It gets slightly stronger each time and suddenly after a few attempts it just triggers the flow.

Any ideas for a good (easy to use) photo hosting website. I used to use photobucket but it's stopped working! KE

Well I'm happy for you that you get it working. Its a brilliant idea actually the pointing up of the elbow makes the horizontal easy to fill with water. How long is the bend is it just the fitting?


a thread on how to post photos

viewtopic.php?f=4&t=21754&p=546380&hilit=how+to+post+photos#p546380

It's a 90 degree bend about a quarter of a 20cm diameter circle not a 90 degree corner of a square although I don't see why that wouldn't work either. I did have to adjust it a few times at the beginning to get it just right but now I don't touch it at all.

I'd have to go back through your posts as I've forgotten but what size bed are you going to have? If it's an IBC (I think that's right, we call them 1000ltr cuve) cut to 30cm deep then this siphon works a treat and I can try find a photo website and get some photos on here.

I'm going looking now........ KE

I have a question, how would a ball valve differ from head height? or are they the same? For example and Active Aqua 550 throttled to about 250GPH because it moves water vertically 5ft?