Aquaponics - The bullwinkle sequencer build

I thought I'd put all this in one place to make it easy to link to.

Some of this is covered in previous posts, but it will be easer to follow if its all wrapped into one post.

The aim here is to make a device that will transfer water from an aquaponics fish tank, or sump tank, to different grow beds in turn. This means you can avoid dry fish. A condition fish hate.

There are existing methods to do this (I've made two other versions myself), but this is the simplest and most inexpensive way I could come up with. It also looks like being very reliable, and could probably be made from scrap. 

The device works by creating a free moving but balanced tube that fills with water. There are holes in each end to let the water out, but there is a float inside that restricts the water in an interesting way. 

When the tube is empty, the float rests in the hole, and blocks it. When a pump on a timer is switched on, the tube fills until it becomes top heavy. The device then tips, and the float drops out of the hole that is now tilted up, and comes to rest on the water until the pump is turned off. The float then settles in the hole at the other end of the device, and the process is ready to repeat.

So the float in this case is used, sometimes as a thing that floats, and sometimes as a thing that sits on the bottom, and blocks a hole. I wasn't completely certain that I understood the universe in this respect but thought it should work. I testing it like this...

Then confirmed it was worth building with this proof of concept.

Which worked a bit, but the float got stuck on my professional brown tape sealing technology.

But I made a proper one. It's called a Bullwinkle sequencer, and it looks and works like this [Edit from the future - When you watch this next video, make sure you have captions turned on, there is a stack of extra info in the captions]...

To build one, you need some PVC parts. I used 90mm storm drain fittings...

You will need...

a T-junction
2 short lengths (50mm or so) of 90mm tubing to fit your T
4 end caps
a 500mm length of 90mm tubing

You will need a ping pong ball, a drill, a length of stainless steel or wood to act as the axle for the device to pivot on, and a way to cut PVC tubing. I used a hacksaw and an electric jigsaw.

I also used a stainless steel ruler, but any long thin weight with a hole for the axle to go through would work.

I cut two holes a bit smaller than a ping pong ball, and used a hole cutter saw for this as described bellow. Another way might be to drill a hole and then enlarge it with a file. It might also be possible to buy a PVC component that is an adapter for one size pipe to the size down from it. This might negate the need for cutting holes at all.

To start with, drill a hole in your T-junction from both sides as shown. 

This will be where your axle goes through. 

Another, perhaps better method might be to glue two washers where I have drilled the holes. This way you could avoid the holes and therefore avoid have a metal bar running through your T-junction. With the washers, a bar could be placed into the washers from each side to achieve the same result. The washer would act as a seat for the axle.

I've used an iron axle for this demo because I had it handy, but its probably better to use stainless or plastic or even wood to avoid contaminating the water and harming your fish unless you use the washer method mentioned above. If you used the washers, the water wouldn't come into contact with the axle at all.

I used some lids from a powdered sports drink container for the flow control caps, but normal PVC end caps would be fine.

The only reason I used these is because I had them and didn't have the end caps.

These caps control the flow out of the device, and as such, it's important to drill the correct size hole. 

I was planning on testing this with my very tired little pump that only puts out 70LPH so that is why the holes are so small. These holes represent the exit flow from the device, and need to roughly allow the flow of the same amount of water that your pump delivers.

The device is quite forgiving with different flow rates, but you still need to make these holes so that they drain water at roughly the same rate as water comes in from your pump.

For this reason, I would recommend you drill a small hole to start with, and only glue them in place after you have established they are correct. It might even be possible to make an adjustable one, but I'll talk about that a bit later.

The flow cap fits over the cap that hold the ball. 

It's important that there is enough clearance, and that the ball can seat freely in the hole in the float seat cap without hitting the flow control cap. To this end it might be useful to add another pair of spacers (a short length of 90mm PVC.

didn't bother with the spaces. but I would if I wanted to glue it all in place and not have any leaks. You actually need a spacer here to make a proper join between these same diameter parts.

I cut the holes for the ping pong ball with a hole cutting set I bought for around $7. It looks a little like this. There is a central drill bit and some different sized rings that are made of saw blade.

You clip the required sized saw to the disk attached to the central drill bit, and you are all set to cut a hole.

I can now make PVC eggs
I cut holes in each end cap so that a ping pong ball would sit neatly in them. These need to be a reasonable fit but it doesn't matter if they leak a bit. 

Any leaks just flow into your grow bed and only for a few seconds before it tips.

It might be possible to add rubber seals to stop leaks, but I wouldn't bother, even on a real world device I was intending to put into use.

PVC tubing cuts really well with a standard hacksaw, and I cut Two short sections (around 50mm long) of 90mm PVC tubing to act as joiners and spacers from the T-junction to the end caps.

The final assemble order looks like this.

50mm spacer (with the ball in it)
Float seat cap
[This is where the optional spacers would go]
Flow control cap (with seeds written on it)

The length of those spacers isn't critical, but they are needed to make the device more forgiving, and to fit the end caps to the T-Junction. When the device is flowing freely, and adding water to the grow bed, the height of the water in this tube (defined by the length of the spacers) gives rise to a condition where the water level finds its own comfort zone. It's important for your water to be comfortable. It does this by regulating it's pressure by it's height in the tube. Remember the tube is sitting on an angle once its committed to a side. If there is more water flowing in than flowing out, this makes the water level rise within the tube. This could be a bad thing because it would overflow if not for an interesting fact. 

When the water level rises, the pressure at the exit point also increases. This means that, within reason, you can vary the amount of water flowing in, and the system will cope. A higher water level in the tube, means higher pressure, and therefore higher flow from the exit through the flow control cap. This is the bit I'm most proud of. The longer the spacers, the more forgiving the device will be. You still have to match the hole in the flow control cap roughly so that it will cope with the input from your pump, but the spacers make it so that you don't have to be accurate.

The size of the hole in the float seat cap determines the maximum flow that can pass through the system. 

These holes are around 25mm but that is only because I'm using a ping pong ball as a float. 

If you needed a bigger flow, all you have to do is get a bigger float, and cut a bigger hole. It might also be possible to use a PVC fitting that reduces from one pipe size to another smaller pipe size, rather than drilling holes at all. 

I found large foam balls at a craft store, but you might find them at a fishing tackle store, or even inside a Christmas decoration if you do Christmas where you live. A child's toy ball might also work. Ask first. The last thing you want is a cranky child when you are trying to make a water diverter.

Almost anything can be used as long as it's fish safe. It doesn't really need to seal all that well because any leaks just flow into one or the other grow bed. As soon as the device tips, the float is no longer acting as a seal, so any leakage not only goes to your grow bed, but it only lasts a few seconds.

This is what it looks like from the outside.

Next we need to make one of these. This is the extension gutter, and is there to bias the weight.

This bit is also very important to have, but it doesn't need to be all that accurate. I didn't measure any of my cuts or drilling on this prototype and it all worked first time. Even without being glued together. Its actually the pressure applied by this gutter than held the entire thing in place.

When you first start the flow, the ball is sitting at the bottom, under water, held in the ball seat cap hole by water pressure from above. If the ball displaces enough weight of water, the device will get top heavy when it fills, and tip as required. If the ball is too small, and the device is on say a 45 degree  angle, water might start to flow from the hole in the flow control cap at the top end, before the device has become top heavy. If it never gets top heavy it will never work. The extension gutter holds water and creates weight in the section that is uppermost at this stage. This means that, as far as the water is concerned, the tube is always longer on the side that's in the air. All the water on the down facing end drained away ages ago, so the extra water held in the gutter creates the desired top heavy weight bias, and decisively tips the device to switch to the other grow bed.

I made my gutters quite long, because I wanted to run my Bullwinkle sequencer, so that it would only rock 20 degrees or so. I would stop it going further by placement of the gutters that would take the water to the grow beds. This would mean my very tired pump would only need to pump water to around 150mm higher than it does now.

I think that if the gutters were shorter, it would need to be allowed to tip to a greater angle to hold enough water to create the top heavy bias required. A steeper angle might mean the sequencer would have to be raised higher and the pump would need to work harder. But then again it would be shorter so who knows. 

Only a small fraction of the length of the gutter fills with water before the device tips when it's operating to the angles shown on the video. I didn't experiment with changing the gutters because it worked the way it was. 

Basically, the gutter helps to make a Bullwinkle sequencer more forgiving of different operating parameters.

The gutter was made by cutting a 500mm length of 90mm PVC down its length.

This is done so you can slide a 90mm pipe over other 90mm fittings.

Then I made two cuts in the middle about 120mm apart that went approximately half way through the PVC pipe.

I was very casual and did all this by eye, but I guess if you were building one to use for ever, you might want it to look a little neater.

I'm not so good with neat, so I'll leave that bit up to people who are.

This cut out needs to be just big enough to fit the T-junction. It would be easy to make bigger if needed.

Next, I drilled two holes at the bottom of the cuts, to allow me to get the jigsaw in.

I cut the sections out and removed them.

You could use tin snips, or perhaps even a sharp knife or scissors.

Pry apart the gutter a little and force the T-junction in. 

Make sure you have already fitted the spacers, and float seat caps. 

I left the flow control caps until last.

Keep forcing the T-Junction along the cut gutter.

Remember none of this was glued, so it doesn't really matter. I'd leave everything un-glued until it was tested. Partly I left it unglued so I could pull it apart and take photo's, and now that it's in pieces I'll just reuse the parts for something else.

Until it falls into place.

Now all that's left to do is add the axle, and the flow control caps.

I also added a stainless metal ruler when I put the axle through. 

When the device has finished it's cycle and the pump is off, the ball drops down into the float seat cap's hole. Because the ping pong ball is so light weight, the device can almost come back to a balance position. This could give rise to a condition where, say because of the way the water came in a slight angle, it might make the same side trigger twice in a row. By the addition of the ruler, the device stays where it was when the pump was switched off. Perhaps a better way would be to add a marble in a sealed tube*, or a sealed tube filled with water. This could be attached on the side or underneath running the length of the device. All that's required is that there is a weight to hold the device where it was when the pump turned off, and that weight will shift to the other side when the device tips. If the ball was heavy enough that would probably do. The ideal would be a ball that only just floated. 

Even the pig pong would be enough if you added the water right in the middle, and kept the device out of the wind.

As it is, if a bird landed on the device, or it was subjected to a strong wind, it might upset the balance.  It would correct itself, and it starts again from such a condition, but if it happened at just the right time it could make the device water the same bed twice in a row. For this reason I'd put it in a box and put a lid on it, if I was making it for real world use and cared for perfection.

Lastly, the flow control caps need to be put in place.

If it happens that the holes that seat the float are the correct size for your flow, these would not be required, but I find its always good to have a component that's easy to adjust and or replace to set your final flow. 

You could use a tap on the exits to set the exit flow rate, or you could make two holes in 2 disks and rotate them so they don't quite align to make the size of the exit hole adjustable.

It might also be of use to mount the exit hole high. This might trap some water once it was all glued in place and negate the need for the ruler or marble tube, to bias weight and hold the Bullwinkle sequencer in the position it was in when the pump stopped.

If I was making one for real use I would definitely explore that before committing to the ruler, although the marble would be pretty easy to implement. Simple is good though.

As mentioned, this Bullwinkle sequencer is designed to switch sides every time a timer turns off the pump, then turns it back on again. But it can also be used with a pump that is always on. The only difference is that you need to adjust your flow with a little more accuracy. If the flow matches the holes in a way that allows only a tiny amount more water out than is coming in, your Bullwinkle sequencer will gradually drain and eventually the float will rest in the draining hole, and it will fill with water again, and tip to the other side. The time it takes between swapping sides, is set by the time it takes for the tube to empty and thus, the time it takes for the float to block the outlet.

 It turns out that it's not as difficult to set up as you might think, and I had no trouble making it work. As long as you can adjust the flow going in, or adjust the flow coming out, its very easy to make work.

As far as I can tell, this device is an original design. 
Its my intention that this design should be freely shared with the world. 
I ask that if you make a design based on this, that you also make the improved design freely available to the world. 
That being said, feel free to make, it duplicate it, improve it, sell it and profit from it, or do whatever you wish with it. 

Also, if you make one, please let me know as I'd love to see it use. 

I would really enjoy some feedback on this one. Suggestions, critiques, derisive laughter, whatever. It's as big as my "how to" handmade fishing lures - how to get the most out of your printer. And like the fishing lure post, I feel there is a little more room in my head after getting it out. 

I hope it's useful, and thanks for reading.

*thanks for the marble idea 

[edit from the future - There is some additional material on sequencers. ]


  1. Epic indeed! Thanks for sharing :)

  2. thinking if you used some sort of cup under the pipe to catch water that uses a toilet type system plunger that goes up with water level.

    then the pipe would tip side to side every few seconds / minutes evenly because the outflow from the cup would be less than the inflow which in turn would raise the pipe to make it flow opposite each time it fills a cup. Time goes by, cup drains and process repeats when it comes back to it.

    1. I'm not sure I follow you.

      Is this to avoid having to have a timer on the pump, or as a completely different design?

  3. I think I need to make a better video showing it from the side.

    Also I think I might make one and use it in my system to check it's reliability

    Anyone watching the video should make sure captions are on because there is a stack of information in the captions.


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