Aquaponics - Ultra slow flow siphon solution

I came up with two solutions to attempting to make a small bucket that takes an hour to fill, but then dumps quickly, as discussed in the previous post called "Aquaponics - Ultra slow flow siphon problem".

The first came through a deliberate approach with a tested methodology, the second came because I recognised the first as already existing. (It made me think of another problem, leading me to find another solution, and that looked a bit like a deer scarer)

It's a deer scarer.

Actually the first solution is also a solution for some other problem, so I think I'll save it for solving that.

A deer scarer works by having a tube pivoting around a point roughly in the centre like a set of scales. One end is blocked and made slightly heavier. The other end is made slightly longer. Everything is set up in such a way as to make the thing sit with the open end up.

If you add a trickle of water to the open end, it eventually fills the tube. when it does it reaches a point where the water in the longer end overcomes the extra weight in the heavy end, so it tips.

Thanks for the use of the pic Cassiopeia_sweet

It looks like this.

Genius.

Once the water is dumped, the heavy end thumps down onto a stone making a pleasant (yet apparently scary to deer) sound, that eases you into the now.

My version would be quiet.






My version would also be less graceful. If you made it out of 200mm PVC tubing you could dump a bucket full of water each time in a short compact unit. You could also place it somewhere else and pipe the sudden dump of water to your grow bed.

So...

To make a grow bed flood for most of an hour, drain suddenly, then flood again, this might work.

Create a bell siphon that has a standpipe too large for your pump's flow. This will mean the siphon wont trigger, but the standpipe will allow water to circulate back to the fish tank or sump just by normal overflow through the standpipe. In other words, it will act as a constant flood grow bed.

Next mount a deer scarer above the siphon and divert a trickle of water from your pump to it, so that it tips once an hour (add a tap on the outlet for adjustment).

The sudden rush of water into the siphon area will be enough to decisively trigger your oversized siphon, draining all the water in mere moments to everyone's delight. So now we have a "mostly flood, and some drain" system. We also have an interesting, steam punk, bit of low tech kit moving around, rather than the sedentary vista provided by a constant flood grow bed.

This could be configured so that your grow bed drained every 12 hours or any desired time, making sure you had no dead areas of rancid mush hiding in the corners of your (almost) constant-flood grow bed.

Thanks Japan.

Thanks deer.

Thanks Nom*.

*[note from the future - someone has created an excellent example of just how such a thing might work.
http://www.youtube.com/watch?v=GSXqr3VdYyM
and I love it when someone goes to the trouble of making something out of clear plastic just to show us. 
http://www.youtube.com/watch?v=4oS0mNApYqw
Thanks for the heads up Nom. ]

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 - Poop

Common practice is to spread your solids fish waste evenly over the grow beds so as to avoid creating dead areas depleted of oxygen, and perhaps containing too much nutrient for the plants. People often add composting worms to their grow beds to aid in the break down of fish solids. The normal method of distribution, is to split your incoming water into several outlets. This is often done by making a loop of hose that surrounds your grow bed, and drilling holes so water enters from all around.

I'm trying something a bit different. [note from the future - I'm currently engaged in a debate as to this being a good idea or not, so copy this approach at your own risk (even slightly more than everything else of here should be copied at your own risk)]

A few weeks ago I tried adding the water directly to the siphon area. Rather than going through the grow bed media, it just feeds into the gap between the media screen and the siphon. What this means is that the clear water spreads throughout the media, but the solids get dumped back into the fish tank.

Normally, the point is to try to get the solids out of the fishtank, but this way the solids get broken up each time they get dumped back into the fish tank. they just seem to vanish after going through the system a few times. At any time, when you look into the water, there is about the same amount of solid fish waste in the water. It's normally queued up in a bit of a whirlpool that forms near the pump. At any one time there might be a teaspoon of solids and bits of who knows what in the little pile.

It's possible that this will all end in disaster, but it's also possible that this is a viable method of mechanically breaking down fish solids before they do into the grow bed.

Because I'm lazy, it's also worked out nicely that I didn't even have to make anything. All I had to do was extend the pump hose so it would reach the siphon.

There is some chance that the solids are building up on the far side of the media screen (in my case, the soft drink bottle that keeps the grow media away from the siphon) but the water rushes to the siphon quite quickly once it triggers, so I suspect it would draw any solids back through the screen and into the fish tank.

I'm keeping a close eye on it and will let you know if any further developments manifest.

By the way, that's strawberries at the top left, three week old coz lettuce (from seedlings) top right and bottom, and the little ones in the middle are baby spinach (also planted three weeks ago from tiny seedlings). Interestingly I planted the spinach on a hot day in the middle of the day and they all wilted to the point where I was sure none would live. Two days later they were still alive but were all wilted to the point of laying flat on the ground. But now every single one is thriving.

We should be harvesting individual salad leaves within a week.

Aquaponics is like intensive care for plants.

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.

Aquaponics - New system

I did a bit more to the new system today, and undid a bit of what I had already done to balance out my progress, and maintain my standstill.

many small holes make one big hole

After carefully cutting the soon-to-be-grow-bed tanks in half, and patching holes, its a bit nerve racking to make a new hole for the siphon. I started by drilling holes because I have a drill, and find it much easier to use tools that I have rather then the imaginary tools on my wish list. The imaginary ones always go blunt too quickly.

not so round

a bit round

round

Next I decided the black poly pipe capping I made from all that poly I like to horde wasn't going to be good enough, would look too tatty, and have fractionally more sticking up bits willing to catch on gardening clothes than I normally enjoy. Given that I'm planning to be gardening with this grow bed for years, I thought I might do it properly. Tomorrow I'll get some PVC conduit to cap the grow bed edges with.

When growing produce with aquaponics, you don't really need gardening clothes.

Aquaponics - Success

Success! I've actually managed to out-smart my fish. This last thwarter was made from a plastic mesh designed to keep leaves out of your gutters.

It's a good thing I'm learning on my small blue barrel system. I'd hate to be making all these adjustments on, and drilling holes in, my big system.

I just spent an hour trying to get my auto siphon to work again.

In order to prevent my fish tank from getting too cold overnight, I tried turning off the pump during the hours of darkness (I now have a small air pump for oxygenation). The downside to this was an increase in ammonia and nitrite levels.

- The nitrates values are divided by 100 so they fit on the graph. (I'm told nitrates can safely be over a thousand, so nitrates are not a concern)

I think my nitrite and ammonia levels are still within safe limits, and it was only for one night, but I've decided to go back to running the pump overnight.

Aquaponics - Sequencing

An ideal aquaponics system has twice as much grow bed as fish tank. The problem is, once you have twice as much grow bed as fish tank, when the tide is out your fish tend be walking around slightly more than fish tend to enjoy. The grow beds takes so much of the water that the fish tank becomes uncomfortably low.

If you fill one grow bed, and then the other in turn you will remove less water from the fish tank at any one time as there will always be another garden bed draining water back into it. There are a few products you can buy to achieve this, but pictured here is my first attempt at in invention to make this occur. Basically its a sea-saw where water is diverted from one side to the other when a float raises to the point where the sea-saw tips, diverting water to the other side. The sea-saw's floats are set at just the right height so that it tips to the other side just before the auto-siphons trigger. The siphons are triggered by the other smaller flow (water flows are all constantly on, and are pictured here as the blue arrows pointing down from the top) I made one of these and it seemed reliable enough even though it looked a bit like it was made by Homer Simpson. 

I don't intend to use a sequencer in my system as I'm going to use CHIFT PIST (Constant height in fish tank, pump in sump tank) which means there will be plenty of water for everything. If space is a problem a sequencer may be the solution. Aquaponics often involves compromise when building a system, especially on a budget, so I thought I would post this just in case it is useful.

[edit from the future - There is some additional material on sequencers. Readers might find this newer version in a post titled  The Bullwinkle sequencer build of interest. It's a better design, and only costs around AU$15 to build with off the shelf PVC components]

Aquaponics - Flood and drain

Plants seem to like it when their roots are not too wet and not too dry. Goldilocks would have us set the moisture level juuuust right, but in aquaponics, there is a better way. Flood and drain.

In our blue barrel system (pictured here at day one) we have half a barrel at ground level as a fish tank, and half raised above the fish tank as a grow bed (within the online forums you will see FT as fish tank and GB as grow or garden bed)
                                                                                                                

This allows us to pump water up to the grow bed and have it drain back down with gravity. But rather than have it running all the time the plants prefer to get some water, then some air, to their roots. One very simple way of doing this is to use an auto-siphon.

An auto-siphon allows us to fill the grow bed with nutrient rich water to a predetermined level, and then have the water dump back out into the fish tank bellow, exposing our plant's roots to the air. Plants love that kind of thing. And the fish love the circulating water. Keeping the water moving oxygenates it and running it through the grow beds filters it.                               

A bell auto-siphon would look something like this if someone were to make an animation of one working ...

- water is pumped in at the top from the fish tank (FT not shown)
- when the water level rises to the top of the standpipe (the standpipe is the innermost pipe) it starts to overflow.
- As the standpipe fills and the water flows down the tube and back into the fish tank, it forms a siphon.
- the small amount of air left at the top of the bell (the bell is the bit that surrounds the standpipe) is sucked down with the water and the grow bed quickly drains back into the fish tank.
- when the grow bed level gets to the bottom of the bell the siphon is broken and the draining action stops
- the water is always running in but the siphon is designed to allow water to flow out faster than it comes in
- the result of this is a flood and drain cycle that plants love.

Other beasties in the grow bed love this flood and drain as well but more on that later.