Updated 20 Nov 2022
Developed by: Daniel Connell
English Tutorial Text: Daniel Connell
Tutorial Animation: Daniel Connell

Contents of this tutorial:

Step By Step Instructions


This is a siphon action pico water turbine which uses water momentum to drive an alternator/generator for producing electricity, or air and water pumps for cooling, irrigation and similar.
The turbine is made entirely from easily sourced off the shelf materials, and should cost about $30-$50 for the unit itself, plus however much pipe you need to attach to take full advantage off your watercourse.  
The turbine can be fabricated by one person in 1-2 days with basic hand tools (mostly just a drill) and should produce 200 watts at about 60VDC(rectified) x 3.3A with a 3 meter drop and 30-40 litres per second flow. This will of course vary according to local site specifics, material dimensions, and overall setup.


Power Drill

4mm, 5mm, 8mm, 10mm, 12mm Drill Bits

Tape Measure
Or other kind of measure / ruler.

Marker Pen

~34mm Hole Saw

16 Hole Saw
This can also be a Spade Drill, Circle Saw, Step Drill, or anything else that will make a 16mm hole in plastic.
For cutting PVC pipe and probably steel thread.
Also a wood saw.
One of 7mm, two of 13mm.
Metal File


Computer and printer
Low quality black and white is fine.
And 2 pieces of A4 or US Letter paper.
13mm Socket / Nut Driver


1 x PVC 45 degree Y Connector
The size will depend on your site specifics, but something like a 110mm to 160mm size change connector is usually a good starting point. Make sure it's double socket not triple, ie it has rubber sealed female connection points on the top and inlet, but not the bottom outlet.
1 x PVC End Cap
To fit the top inlet of your Y connector.
1 x Hoverboard Wheel
A wheel from a hoverboard / balance board / Segway / eScooter.
You can usually get a whole board second hand from the local classifieds for about £$€20-30. If nothing like this is available in your area probably the best option would be a motorbike alternator.
1 x 120mm Computer Fan
The standard seven blade flat pitch fans are best. A server / high RPM / fibre reinforced type will be stronger, which may be necessary for higher drop turbine installations, tho we will be reinforcing these with heatshrink.
Battery Pack Heatshrink
180mm flat width dimension should fit a 120mm PC fan. You'll need 50% more than the height of the fan.
1 x Plastic Chopping Board
Any kind should be fine, as long as it's 9-10mm thick.
1m x M8 Threaded Rod
Stainless / galvanised / zinc coated steel.
4 x M8 ~50mm Hex Head Bolts
Stainless / galvanised / zinc coated steel. Need to be long enough to go through two thicknesses of the wood you're using.
1 x M8 ~30mm Countersunk Head Bolt
Stainless / galvanised / zinc coated steel. Driver type isn't too important, but allen key is probably most useful.
14 x M8 Nyloc / Lock Nuts
9 x M8 Nuts
12 x M8 Penny Washers
About 30mm outer diameter or so.
12 x M8 Form A Washers
16mm Outer Diameter.
2 x M8 Wingnuts
1 x M8 ~30mm Connector Nut
Anything 24-40mm long will do.
3 x M4 70mm Countersunk Head Machine Screws
70mm is if you're using a 160mm PVC Y Connector. If you're using a different diameter pipe these just need to be long enough to hold the plastic ring at center of the outlet. If you end up cutting longer screws down to the proper length, make sure they're all exactly the same length as it'll make it easier to centre the ring.
2 x M4 20mm Countersunk Head Machine Screws
8 x M4 Nyloc / Lock Nuts
5 x M4 Washers
4 x 8mm ID O-Rings
Internal diameter 8mm, 2-3mm thickness, generally fatter the better. You may end up using slightly more or less than four of them.
Three pieces of about 50mm x 15mm x 400mm. Doesn't need to be exact. Best if it's pallet wood or something else which is treated to survive outdoors, if not maybe use weatherproof exterior paint.
Flat Aluminum Bar
Two pieces about 24-30mm wide x 2-3mm thick x about 40mm long.


Circle Sheet Template: 3D Models


Full Turbine Model .zip
(62 MB)
Current Potential Best Impellers For 3D Printing
(Google Drive folder)

Step by step build instructions:

Step 1:

Take your plastic chopping board and cut a circle halfish way through it with a circle saw of more or less 35mm diameter. Can also be anything from about 32mm to 40mm.

Using the circle saw pilot hole as a centering guide, drill a 16mm hole through the board with a circle saw, spade drill, step drill, or anything else that will accurately do it.

Complete the larger circle cut using the half deep cut as guide.


Take the resulting ring of plastic and place it at the centre of the circle guide sheet you can download and print out from the Resources section of this tutorial.

Mark the ring with lines at thirds. You’ll want to get this fairly accurate.

If you’re unable to print off the guide sheet, probably the easiest way to find the thirds points is to wrap a length of masking or similar tape around the ring, mark a point where it overlaps, remove, measure that length, calculate and mark thirds, rewrap the tape and mark the ring.
But the circle sheet’s a lot quicker.

Mark the third lines at half the width of the plastic and drill a hole through each. Strictly speaking a 4.5mm hole is best, but if you don’t have a bit that size 5mm is also fine.
You’ll want these to be fairly accurately aimed at the ring centre, a small vise and a pillar/press drill is useful if you have one, otherwise whatever drill you do have and a steady hand.
If you’re not happy with the results there’s plenty of plastic in your average chopping board for second chances..

If there’s any plastic been pushed by the drilling into the 16mm centre hole then clean it up with a knife or drill, so that the inner wall is fairly smooth and uninterrupted.
Check that your M8 Form A washers can sit within this circle with little clearance, but enough to turn without rubbing. If not, enlarge the hole as required.


Take your PVC junction connector and also centre its outlet on the guide sheet, aligning one of the seams in the plastic with a third line on the sheet.

Mark lines at the three thirds points, and the two half points. Mark the thirds lines with a mark 1cm in from the edge.
If you don’t have a guide sheet the same masking tape technique from the previous step will also work well enough.


If your impeller is smaller than the outlet of your PVC connector you’ll need to build in the wall to meet it, minus a couple millimetres clearance. This can be done with a 3D printed flow guide, but if you’re not printing any components then usually the easiest way is to cut short lengths of PVC pipe of the diameter which fits the connector outlet (ie, that you’ll be using as your outlet tube), and remove sections of their wall so that they can be squeezed down and nested in each other inside the connector outlet.

Make each section shorter than the one it fits inside so that you have a bit of a gradient to and from the impeller. This doesn’t need to be precise, so just eyeball it.


Drill 4mm holes through the 1cm marks on the thirds lines, through the connector wall and each of the nested pipe sections. Best if one of these goes through the gap of at least the innermost section, as it’ll help keep the loose ends locked down.

Countersink the holes with a 10mm drill bit (or whatever the size of the head of the M4 machine screws you’ve got to put there). It’s recommended to do this with the drill in reverse, as otherwise you risk just drilling a 10mm hole where you really don’t want it.

Insert your M4s. Place a washer on each and wind a nylock / lock nut about halfway up the thread. This is definitely easiest with a driver bit in your drill and a 7mm spanner, but feel free to use a manual screwdriver if you’re some kind of purist.
Repeat with a second nylock on each.

Place your plastic ring with all three M4s inserted in the drill holes.
Wind the first nylocks almost to the wall, but not completely tight.
Wind the second nylocks down to meet the ring.

This is the point where you’ll want all three to be exactly the same length (if you’ve cut them down to the right size from longer screws) as you can see how much clearance their ends have with the plastic to centre the ring.
If they protrude at all into the 16mm hole they are too long.

When the ring is nicely centred, tighten the outer nylocks against the wall so that the whole assembly is rigid and strong.
The screw heads should be flush or slightly recessed in the outer PVC connector wall.


Centre the back top opening of PVC connector on the guide sheet, again aligning to the same seam as previous, and mark lines at the half markers (ie 90 degrees each side of the seam).

Use the guide paper edge, or any other kind of ruler / straight edge (easiest if it’s somewhat flexible), to mark lines down the sides of the connector joining the top and bottom half mark lines.
These will want to be accurately straight down the connector sides.

Mark both lines at 20mm and 100mm from the start of the flat wall, below the top flaring.

Drill these marks with 8mm holes, or whatever size bolts you’ll be using to connect the wood (keeping in mind that M6 is too small and M12 is too large).


Cut four pieces of wood, two of which are 120mm long and at least 30mm wide by 20mm thick, and two of about 400mm long by at least 35mm wide and whatever thickness.

If your wood isn’t treated for outdoors use it might be a good idea to give it a coat or two of weather resistance paint.

Drill all four pieces with the same size bit as in the previous step at 20mm and 100mm from one end (so the same 80mm gap between them as you just made in the PVC).

Place the two shorter pieces on the sides of the PVC, and the longer pieces on those, and attach with four bolts, washers, and nuts.
If any of the holes don’t exactly line up, or if the bolt threads are engaging the wood making them hard to tighten, redrill the hole with a bit 0.5 – 1.0 mm larger.


Take the PVC end cap and accurately drill a 10mm hole in its centre.
I find the easiest way to do this is balance it on a nail or other pointy thing in a bench vise, nudge it til it’s nicely flat, then press the plastic on to the point and drill out the indent.

If that’s not an option for whatever reason then you should be able to use the guide sheet, making sure it doesn’t slip when you turn it over.

Insert the cap into the top connector opening. Silicone or similar gasket lubricant can make this a bit easier. Dish washing liquid isn’t a great option as it can corrode the rubber seal over time.


Take your hoverboard ( /eScooter /Segway) wheel, remove the screws in the back, and separate the front half from the back. This can take a little bit of force, I find the easiest way is to put the wheel axle in a bench vise and (carefully) make use of a mallet.
Slide off the tyre using a similar method.

The back half, or stator, is the one with the wire coils. The front half, or rotor, has the magnets. Try not to get any steel scraps or filings near the magnets as it can be a bit of a hassle to get them clean again and you don’t want any detritus in there while it’s running obviously.

Drill a very accurately centred hole in the middle of the bearing mounted on the inside of the rotor.
The easiest and most precise way to do this is to put an M8 nut or nylock inside the bearing, as it’s just the right size, and then drill through the centre of that with a 6mm drill bit, which should again nest nicely.
(The most perfect would be to use 7mm bit and pre-drill out the nut threads, but only if you can be bothered).

Remove the nut and enlarge the hole to 10mm.

Countersink the inside of the hole with a 12/13mm bit or anything else which will do that job, again probably having the drill in reverse as you only want to go halfway through the metal at most. Countersink a little, check you haven’t gone too far, repeat as necessary.


Take a countersunk head M8 bolt and grind down the head so that it fits in the hole in the HB wheel rotor. Easiest is putting the bolt in a drill and running it against a bench grinder wheel, or a metal file if you don’t have one of those.

You want to leave a couple mm for it to not come out of the hole, but not too much that the HB wheel stator axle will hit on it when it’s all reassembled.
Err on the side of too much metal, as you can always just put the wheel back together, spin it to see if anything’s making contact, and removing more bolt head.
Whereas too much means starting over with a fresh bolt, which isn’t exactly the end of the world.

Place the bolt facing out through the hole and wind on a wingnut til it meets and marks the metal of the rotor’s outer face.
Remove the wingnut and bolt, mark the face with a pen 2-3mm outside of the wingnut marks, and drill those with an 8mm bit, being careful to not go through to and damage the bearing sitting just behind.

Replace the bolt and wingnut so that the tips of the wings are sitting within the 8mm holes with enough leeway that the bolt can swivel a couple degrees in all directions. If the holes aren’t large enough or properly situated for this then enlarge up to 10mm / as necessary.

Wind on a connector nut and tighten against the wingnut, making sure the bolt assembly can still wiggle.

Reconnect the stator and rotor, and replace the screws.
Hold the axle and give it a spin to make sure everything seems happy. There will be some resistance from the flux of the magnets, so should only do one revolution or so with a firm push.


Place the HB wheel with a roughly 10mm space of some kind between the connector nut and the PVC end cap. Mark both pieces of wood at the level of halfway along the flat section on the wheel’s axle.
Place the wheel to one side.

Draw a line on the outside faces of both bits of wood at the level you just marked, and two marks on that at least 30mm apart, ideally about 40mm, depending on the width of the wood. Drill these with 8mm holes.

Cut two lengths of flat aluminium bar of about 50mm, and drill two 8mm holes in each at the same spacing as the wood.

Cut two lengths of M8 threaded rod to about 260mm (or basically whatever length is going to span the bits of wood with at least two nut widths either side).
Wind two nuts onto one end of each and lock them tightly together.
Place both through the holes on one bit of wood.

Place on each a washer, two nylocks, the two bits of aluminium, two more nylocks, and another washer.

Using a 13mm socket in your drill and a 13mm spanner (you can do this with two spanners, but it’s much quicker this way) wind the first nylocks to almost meet the wood, then the second nylocks to just over halfway along the threads, then the alu and third nylocks to almost meet them, and then wind out the fourth nylocks to meet the inside of the second bit of wood.

Place a washer and a nylock on the end of each thread and tighten the nylocks of all four ends against their wood.
Position the middle four nylocks and alu slats so that the gap between them is more or less centred over the hole in the PVC cap, and with enough space to place the axle of the HB wheel.


Place the HB wheel.

Tighten the nylocks so that the alu bends around the axle, holding it firmly with a ~10mm gap between the connector nut and the hole in the cap.

Check that both pieces of wood are accurately at 90 degree right angles from the end cap, using a set square / piece of printing paper / anything else with a perfectly square corner.


Cut a length of M8 threaded rod of about 400mm length (from hereon referred to as the shaft), or whatever is going to fit what you’re using as an impeller if not a 120mm PC fan.

Place this through the cap hole and wind in to the connector nut til tight.
Mark with a pen where the plastic ring bush sits, remove the thread.

Place a nylock, a stack of about ten or so M8 Form A washers, and two nuts locked tight to each other. Adjust the nylock so that the washers can spin freely, but not wobble.

Reinsert the shaft and wind into the connector nut.


Adjust the placement of the HB wheel so that the M8 threaded rod is nicely centred in the 10mm cap hole.
This is done by winding in and out the nylocks holding the aluminium. All four for moving in the direction of the top threads, and by opening out one side and squishing in the other to move the wheel laterally.

Feel free to deploy careful use of a hammer or mallet to make the adjustments.

Once it’s well enough aligned, lock down all the nylocks so that the wheel is securely held.

Wind out the shaft from the connector and place on it in order away from the PVC; a large washer with an 8mm hole, a smaller 8mm washer, and as many O-rings as required to fill in the gap to the connector nut.
You want to take advantage of the springiness of the O-rings to make sure there’s no gaps that air could be sucked in through.

If your PVC cap has any raised text or other features around the hole then you'll probably want to glue some flat plastic or similar so the washer sits nice and flat.


If you’re using a 3D printed or otherwise earlier prepared impeller, this is the point at which you attach it to the shaft and turbine’s complete.

Otherwise, to use a PC cooling fan, remove the fan itself from its housing assembly, which usually involves cutting and otherwise destroying any non fan bits, and punching out the steel pin axle.
Don’t worry if this leaves a somewhat jaggy and off centre hole, we’ll be correcting for that in a sec.


The decision to remove the magnet strip or not will mostly come down to which of your available circle saws is best going to fit, one way or the other.

Take that saw and cut a circle of plastic chopping board. It’s most likely not going to exactly snugly fit into the fan housing, so make up any difference with several winds of electrical / masking / other tape.
Cut off the excess tape width down to the level of the plastic.

Drill two opposing 4mm holes through the plastic circle and fan housing, about halfway out from the centre hole.

Insert a countersunk head M4 machine screw into each of these and secure with a washer and nylock.

Enlarge the centre hole to 8mm. It should still be nicely centred, but if it’s not you’ll need to start over.


Measure the height / thickness of the fan and cut a strip of battery pack heatshrink which is that plus 50% extra.

Shrink this on to the fan. You can use a heat gun / gas range / maybe hairdrier, but I find the easiest and most precise way is just in a little pot of freshly boiled water.
It’s fairly easy for the heatshrink to slip off the tips of the fan blades, so best is to dip one little bit briefly in the water while holding everything in place, then again for the opposite side, than quarters, readjusting the heatshrink as necessary, then roll the perimeter through the water until everything’s nicely locked down.

If this goes wrong, heatshrink is cheap and you’re not using much of it per go, so just cut it off and try again.
Fairly easy though.

If you can’t get heatshrink in the right size, probably best option is to cut two strips of soft drink bottle plastic, (small) pop rivet them together into a ring that’ll fit the fan, and use exactly the same technique as above.


Place the fan assembly on the shaft, push up to meet the nut, wind on a wingnut til its wings almost touch the two M4 screws, pull the fan down to the wingnut, and wind both back up to the nut.
The direction of the fan’s spin will tighten everything together, so you don’t need to.

Give the fan a turn to make sure it, the shaft, and the HB wheel are all happy.

You’re done!

What to plug this into, mechanically, hydrodynamically, and electrically, will depend on the specifics of your site and setup, so feel free to message me at opensourcelowtech.org@gmail.com, or post on your online forum of choice, such as this one that we run (ostensibly for DIY wind turbines, but questions about hydro are also fine as the considerations are much the same):