Aquaponics - Cluster siphon success

I'm getting more and more confused by this idea of mine by the minute.

But anyway here's a simplified version of the Bullwinkle Siphon working at a range of different water flows. Possible advantages include not having to calibrate it, and perhaps using it in a solar or wind powered aquaponics system where there might be variable flow rates. Within reason it should start and stop without any trouble regardless of flow rate.

One of my better ideas.

Just to clarify, my idea is to have multiple standpipes in a bell siphon. As usual, as far as I know this is an original idea and blah blah blah. I give it freely to the world to make whatever use of as you see fit. Enjoy it, profit from it, hate it, etc etc etc.



By the way the mandarins are just there as packing to hold things in place.

That's all well and good, but this older version is driving me crazy. It should work over an even greater range of flow rates, and did on a few different occasions.

Intermittent faults drive me nuts.

Things should either work or not.

The first attempt at my anything in, anything out original recipe siphon, at least worked a few times. Now it seems I'm taking one step forward, and one and a bit back.

I made a new version of the uber siphon with a little more precision.

Only a little.

But I felt sure it should do what I asked of it.

I also made a nice clear top for the uber bell so I could see all the mini bells inside.

Brown tape is the new PVC.

To recap, it has a cluster of three bell siphons inside a forth.

The forth is set so that it's cut a little lower so that it triggers first.

The plan is that the forth siphon, the one without the glass jar on it, should trigger first, fill the big coverall siphon with water, and thus decisively trigger all the other siphons because of the increase in depth.










But on this version, the forth siphon didn't even trigger!

It's a full centimetre below the height of the others, and yet they all triggered. A tiny amount of water would trickle into the standpipe, then the large bell water height would drop, as the other 3 siphons triggered.

Now what this all means is that all I need to do is make a 3 into one siphon that has an air breather to break the siphon at the end of the cycle and all's well. The thing will do its job just fine as seen in the video, but it's driving me nuts that I don't understand what's going on with that forth siphon in the other version.

It turns out if you agonise over intermittent faults to my invention engine it groans in reply, "Occam's razor".

Go figure.

Aquaponics - Bell siphon sizing not-so-magic formula

A "bell siphon" is a device that automates the flooding and draining of an aquaponics grow bed, even though the pump is adding water to that grow bed constantly. 


This post assumes you know lots about bell siphons. If you don't, you should start here on this post titled "bell siphon".


You probably should have already read this post titled calibrating a new bell siphon.


If you still don't feel you know enough, you might like to read this on flood and drain, look at this upgraded animation of a bell siphon working, watch this video of a glass bell siphon showing what's going on inside, or just skip this post and look at this youtube video of a panda cub sneezing. (personally I'd look at the panda)


It also assumes you don't mind reading something you think will eventually have an answer, but may disappoint.

Before you take anything I say to your design, you should know that my system is run with bits of string and bubblegum holding it together. 


My pump looks like this. I love wire.


Yes, those two opposing loops of stainless wire are the front bearing for my pump. Wire is the only thing supporting the impeller. It's been running that way for 6 months or so, but the output of the pump isn't really enough to run my system. The impeller is the wrong one salvaged from another pump, and doesn't really fit. 


There is no magic formula for weighing up the dimensions when designing or trouble-shooting a bell siphon, but there are some things you can do to make it a bit easier.


The problem, in a convoluted and sprawling nutshell, is this.


There are a huge number of variables in the way the water flows into and out of an aquaponics system. The type of pump you have is a big one, as is the length and width of your standpipe in the siphon itself. But there are other variables that can have dramatic effects. 


So, things that vary input...

• pump output
• height the pump has to pump up to (most mumps are labelled as if the user is going to pump water to nowhere. A pump labelled "3500 litres per hour - Max height 5 metres" might pump 3500 litres if there is no hose attached to it, but add a 5 metre hose and it will only pump 1 drop per hour. The amount it will manage at any given height in between are anybody's guess unless it comes with a graph indicating approximate values at different heights.)
• restrictions to flow caused by corners and other bits that people use to distribute the water around their grow beds.
• total length and diameter of hose used (there is a surprising amount of friction in shifting water through pipes)

And things that change output from the siphon, and how the siphon triggers might be...

• width and height of bell
• width and length of standpipe
• freedom of water movement through the media and media screen (if you are drilling holes in the media screen, drill them all at the bottom - if the holes at the bottom cant drain enough, the ones at the top are not even going to be in play when the water level gets lower. The end result is that some kind of equilibrium can be reached where water coming in matches water going out through the siphon. In this case the siphon wont ever stop.
• any obstructions to the outlet (uphill sections that might trap air or water, end of pipe being submerged  or anything else that might cause some back pressure)
• changes in width of the outlet. Things like a flange that your stand pipe crews into may well restrict otherwise change the flow. Sometimes a bit of chaos in the standpipe can help create the seal required to trigger the siphon.

The result of all this, is that it's very difficult to say "this size siphon will work with this pump".

Even if you set up two systems with the same components, it would be a good idea to have a tap that will allow you to divert some water so you can fine tune your system. The irregular flow of water can mean some very small changes can have some big effects. 

So, the solution...

Of all these things, the easiest things to control, and thus the best things to start adjusting are...

• Inlet flow. By adding a tap, and diverting perhaps 20% of your water back into the fish tank rather than the grow beds, you have some room to play. ie you have some spare water flow in hand, you can adjust your flow UP as well as DOWN to tune your siphon.
• Outlet flow (Standpipe width) The standpipe is a very inexpensive component, and may even be sourced as an off-cut for free. This means it's easy enough to replace with a bigger one if need be, or filled with a smaller one.

My process for setting up a system would unfortunately involve a bit of essential trial and error.

1. Buy a pump capable of turning over all the water in your fish tank ever hour plus 20% to divert. The diverted water aids in aeration so isn't wasted. (very important for your fish and filtration so pump selection should always be the starting point)
2. Plug it in and look at the flow. 
3. Get hold of a tube for a standpipe that you think will be big enough to dump more water than the pump puts in. My pump runs constantly and takes around 20 minutes to fill and 20 minutes to drain. That means my siphon can dump water at around twice the speed that the pump can deliver it. (see photo's below)
4. Adjust accordingly. Its easy enough to adjust upwards, just drill a new hole and put in a bigger pipe. Downwards is also easy because a large number of hoses and PVC tubes fit the next size down inside them (I presume so you can join them). If you add an inner tube to reduce the width, you don't need to silicone it in place, because it doesn't matter if it leaks. Any leakage is just going into the original pipe anyway. I made mine bigger than I thought I'd need with this in mind. If you really feel the need, it would be easy enough to test it in a bucket. Plug the standpipe and fill the bucket, then let the water flow. If the pump cant keep up with the draining, then you will have no problems as you can always reduce it if you need to. 

That's the magic formula "Its easy to change the inflow and the outflow, so dont worry about it. Just have a go."

Just trust your judgement and as long as you have the tap between the pump and the grow bed, allowing adjustment, it will almost certainly work. If you are making your own system, you already trust yourself anyway, so just go that one step further, and do it. You'll be fine. And perhaps reread calibrating a new bell siphon.

Just out of something bordering on interest, my system runs like this. 

My inflow is from my very sad pump, and flows at around 50 seconds to shift a litre to the grow bed.

So I think that means I'm pumping 72 litres per hour. Which isn't really enough but that's the pump I have. 

I'm getting a new one. 

My standpipe was originally 19mm poly pipe but is now restricted to what my trade quality fridge magnet tape measure tells me is roughly 12 mm internal diameter garden hose.

The rate of outflow is really difficult to see in my real world system, because it drops straight down and doesn't photograph well, so I faked the output in my kitchen sink for the photo. It would look a little like this if I pointed my standpipe outlet to the side.

I warned you it might disappoint. 

If you are technically minded you might want to look at this 

http://flexpvc.com/WaterFlowBasedOnPipeSize.shtml

I'm not, but I'm told it might be useful.

Aquaponics - Calibrating a new bell siphon

This post assumes you know something about bell siphons, and roughly how they work. It also assumes you have made one and want to get it to work. If you need a bit of an introduction to this device, it might be worth reading this post first - aquaponics - bell siphon

With anything that you are trying to calibrate, whatever it is, the most important thing to do is make sure you are changing only one thing at a time. 

It's possible to make a bell siphon work with all kinds of different approaches, but in its simplest form the standpipe drops straight down from the grow bed, and the water flow isn't interfered with in any way

By having your standpipe drop straight down into air the only thing you can change is the flow into your siphon. The easiest way to do that is to put a tap on the inflow to your grow bed, or a tap that diverts some water away from the pipe going to your grow bed, and dumps it straight back into your fish tank. Plastic taps cost about $2. Don't use a brass or galvanised iron one or anything metal because it might poison your fish.

Turn the single outlet from your pump into two by adding a T-junction between the pump and the grow bed.

Make one of your two new outlets go up a bit higher than the other. This one is your excess overflow, and needs to be diverted back to your fish tank. The reason we make it go up a bit higher than the other is so that it becomes the lest preferred way for the water to travel. Water hates traveling uphill, so it will prefer to go into the lower pipe with the tap attached. Only when the tap is turned off a bit will water flow through the higher pipe, and overflow back into the fish tank.

The other outlet gets the tap, and continues on to the grow bed.

before you start...

- make sure your breather pipe is 2cm away from the bottom of your grow bed.

- make sure the breather pipe is breathing fresh air when the water is low enough. Its possible, if the breather is a narrow enough pipe, and is hard against the siphon, to form a meniscus so that it sucks water even when it is above the level of the water. Check that the breather pipe is sucking air when it should be sucking air.

- make sure the water can flow through your media screen fast enough. If you have a screen made with holes drilled in it and there are not enough holes at the bottom, the flow through the media screen can reduce as the tide goes out. This can make for false stops. When the siphon stops, the sudden small amount of water that flows back out of the bell can create a localized increase in water depth. This can reseal the breather, and also kick off the siphon again if it hadn't completely stopped.

Steps in tuning your bell siphon might be (for a tap that is at the end of the pipe to the grow bed)...

1. turn on the tap to a midway position.

2. wait until the water gets to the top of the bell where it should trigger.

3. if it doesn't trigger turn up the tap and go back to step 2. If it does trigger wait until it empties.

4. if the siphon doesn't stop when the grow bed is empty turn the tap down a bit until it does.

5. wait until it fills and see if it triggers properly at the top. If it does, watch it cycle way too many times, drink beer and bang on about it to your friends (I recommend a glass bell siphon to this end). If it doesn't, adjust the tap so the flow is reduced a tiny bit and repeat.

The object here is to adjust the flow in ever smaller amounts until you narrow in on the correct flow. Once achieved, the flow should start within a few seconds of the first flow of water from the standpipe, and should stop quite suddenly. It will probably take 4 or 5 cycles to adjust.

If you still cant get it to operate, there is a fair chance your pump and siphon don't match. Try adding an inner sleeve to the standpipe to reduce its diameter.

Trouble shooting siphons

Any air in a bell siphon should just exit down the standpipe as the water rises and the pressure inside the bell increases. If it doesn't, then there is a fair chance the exit pipe isn't draining freely. With air in the bell, it's possible that your bell might float, and not trigger.

Some people say its a good thing to have some water in the exit pipe, but after a stack of experiments, I found that even though having some water in the pipe often fixes a problem siphon, a bell siphon will be much more reliable if you have a clear, straight down exit that is flowing into just ambient air pressure. That is, dump from your standpipe into fresh air, then catch the water in a drain to take back to your sump, or just drop it straight down into your fish tank if that's your arrangement. At the very least, make sure your drain is running downhill all the way to the end. It makes it a lot easier to get the flow right if your are only dealing with one variable.

The more simple your system is, the more reliable it will be.

Getting your flow right is a much better solution than adjusting your drain by putting bends in it, adding uphill sections, or submerging the end. All of these things can get a siphon to work that otherwise might not, but dumping to ambient air pressure, and adjusting the flow until it works, will make for a very reliable siphon because this makes for only one variable, and with a tap, you have total control over that one variable.

Keep your system simple, and it will reward you with reliability.