Laminar Flow Water Jet for Under $25.




This instructable is for everyone who has ever wanted to build a Laminar Flow Water jet, it sounds complex but it is actually very simple. You will need some PVC pipe, some brass pipe, about 300 straws, 4 test plugs, and some sponges. So lets get started!!!!

Here is a link to my second instructable that shows how to add lights to the water jet.

If you have any questions or comments feel free to leave a comment, I don't mind if it is negative, you can always improve something when it is wrong but one its right there is no improvement.

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Step 1: Supplies

1) A foot long piece of 3 inch pvc pipe.
2) A 3 inch pipe cap.
3) A 6 inch piece of 1 inch pvc pipe.
4) A strong water proof epoxy or similar glue. (i.e. Marinetex)
5) A 6 inch long 3/8 inch brass (or copper) pipe with somewhat thick walls.
6) 200+ straws (if they are the bendy ones it doesn't matter)
7) 4, 3 inch test plugs.
8) Some 5 x 3.5 x .25 sponge/scrubbing pads. (if they are wider then that is fine, you want them to be thin though.)
9) A razor blade or even better a small bandsaw.

 A small razor or exacto knife,  
Sand Paper (light and heavy grit)
Garden Hose
Drill bit that will fit snug into the 1 inch pipe.

Duct Tape
A band saw.
Electric drill
3 inch hole cutting bit(helps to round the 1 inch pipe)
Glue mixing supplies ie. Mixing board, stirring stick, applicator.
Various size brass pipe (for making different nozzles)
Extra 3 inch PVC Caps(these are a little expensive so i just used one.

Step 2: The Nozzel.

Chosing a nozzel can be difficult, but for a 3" PVC pipe a 3/8" brass pipe works very well.

To start you will want to start with a somewhat thick  6" piece of 3/8"brass pipe, first if you have an electric drill it goes much faster, you want to clamp one end into the drill and let the other end move freely. Now the important part get some heavy gritt sandpaper (80 gritt) and roll it into a cone shape with the gritt facing out, now run the drill and slowly push the sandpaper into the end of the pipe the goal is to create an inside taper, once a fine edge is created you need some very very light gritt sandpaper, like finishing paper, (400 gritt) then roll it into a cone and do the same thing so the inside is very smooth.
(Optional but you can also taper the outside of the pipe in the same way just reverse the sandpaper)

Step 3: Nozzle Cont.

Now you want to cut the nozzle off about .5 inch from the tapered end. (the excess pipe can be used to make more or new nozzles) a metal pipe cutting wheel works best for cutting it. Now you want to remove the excess pipe from the drill and put the nozzl into it with the tapered end facing inward, now you have to do the same thing to this side only you just want to remove the ragged edge, you don't have to completely taper it. Once that is done take the nozzle out and roll a piece of fine sandpaper into a tube that will fit into the nozzle, now take the nozzle and slide it up and down over the sandpaper tube but DON"T TWIST IT!!!! You want the sandpaper marks to be stright in the nozzle. (see picture)

Step 4: Inserting the Nozzle

Now take your Cap and drill a 3/8 inch hole and insert the nozzle with the fine tapered end on the inside of the cap as in the picture. Then use some super glue to secure it. (remember it is going to be pressurized)

Step 5: Main Body Part 1

First you will need a drill bit that fits well inside the 1 inch pipe, then use it to drill an offcenter hole in the bottom side of the 3 inch tube as pictured. Then use a piece of heavy gritt sandpaper to round one end of the small pipe so it fits on like in the picture. It helps to cut one end of the small tube to the appropriate angle that way you don't have to sand as much. Now you need the the epoxy to attach the pipe as in the first picture, i used Marine-tex to attach it but quick drying glue would be nice. 

Step 6: Main Body Part 2

Now for the inside you need to punch out the test plug so you have the side and lip left, then use a razor or saw to carefully cut  the top lip off the plug so you make a platic ring with the side of the plug. Now cut one side of the ring so you can shrink it, you then want to cut out a small protion of the ring so there is a gap in it then when you put the ring in the tube by its self it doesn't overlap but instead the the edges of the ring should push together and hold it tightly, you then want to take a sponge and cut it so there is a 1/2inch overlap on the sides of the tube then place it on the tube and then put the ring in it and press the ring and sponge down about an inch past the water intake opening on the bottom of the pipe with the sponge sticking out the sides of the ring as shown. you want it to be as tight as possible in the pipe because the sponge has to hold the straws in place and resist the water pressure.

Step 7: Main Body Part 3

Now place as many straws as will fit comfortably in the 3 inch pipe (inserting the bendy part down if you have it.) Press them down to the bottom sponge (a spraypaint can works well for this) make sure they are all about the same level in the pipe then cut out another sponge and plug and repeat the previous step 6, only push the sponge from the top of the tube so the straws are in between the two sponges, but be careful you don't force the other sponge out the bottom!!!!!

*You can also cut a small piece out of the ring so the sides don't overlap so instead the edges push together, you can also super glue the ends of the ring together just make sure it fits snug in the 3 inch pipe.

Step 8: Main Body Part 4

Finally if every thing is dry push a test plug into the bottom of the 3 inch pipe and secure it but DON'T GLUE IT!! Just press fit it or tape it if you have to. Now the last part fit the top cap with the nozzle and press it on very tightly!!!!

Step 9: Finally

Now with everything secure insert a hose into the 1 inch pipe (conveniently fits) and slowly open the water till you can just hear it flowing and slowly wait for it to fill up and if everything is done right you should have a very nice laminar flow water jet, but wait theres more!!!!!

Step 10: Before Cranking Up the Pressure.

If it works good at low pressure then remove the top cap(if its stuck then sit the pipe on its base, turn the water on so there is a1 inch fountain and cover the hole until it pops off don't worry about it spraying it won't, but be sure the bottom one doesn't come off first if that happens then you need to just try to pull the top off yourself) now take either superglue or epoxy and put a few drops on the plug rings to attach them to the pipe(do this on both sides, top and bottom, otherwise the water pressure will force the sponges and straws up then blow the top off and then continue out onto the ground, which isn't fun) Once the glue is secure you can reassemble, gluing the test plug on with super glue and then just press fit the nozzle plug, very tightly!! and your ready for some serious water jets!!!

You don't want to glue the nozzle plug on in case you need to open it later.

Step 11: Troubleshooting

If you don't get a laminar flow and it looks like the stream isn't perfectly round then you have an obstruction in the nozzle (it may be too small to see) but just take your light gritt sandpaper and give it a final good sanding and that should solve it.

If the stream is laminar then goes to a jet like stream then reduce the pressure and if it doesn't stop then you need to check the inside and make sure the straws and sponges haven't moved. If they are still in place then replce the top and try again, also if you touch the nozzle while its on it can make it do that, just either run over it again or shut the water off and let it sit for a few seconds then turn the water back on (this clears the nozzle of the air bubbles)

If the stream is laminar but it varies in height and kinds wobbles up and down then that is just a pressure problem (gonna try to find a cheap fix for that).

Step 12: Optional

I plan to add a bigger nozzle to hopefully stop the stream breaking up quickly, then i want to add a light system and a cutter which i will try to document better.

Also for info on how it works i will explain:
Water enters the bottom swirls around and finally goes through the sponge which slows the water, then the straws remove the swirling and you get one continuous coloumn of water, then the second sponge slows it again then it fills the space to the nozzle and it settles in the space, then it is forced through a (usually precision cut nozzle) and you have a laminar water stream!!!!

As mentioned in the Supplies section extra PVC caps can be used to create other nozzles and you can use various size brass nozzles if you have extra caps, just remember to follow the same technique when ever making a new nozzle.

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23 Discussions


4 months ago

Laminar flow is ok how to fix led lights


5 months ago

Can you tell me how to build the nozzle cutter,please?


Question 1 year ago on Introduction

Hi, it’s difficult to obtain 3” pipe, will 4” work? Thanks


3 years ago

Have you calculated the reynold number of the flow?


3 years ago

could you tell me the taper angle?


4 years ago


The straws in the direction of flow make the water flow in a singular direction, when the water enters the cylinder from the bottom it swirls like a whirlpool then the straws act like a rudder and steer the water to flow up the chamber in one smooth linear motion so it no longer swirls, for example hold a garden hose with the open nozzle straight up in the air then open the valve a tiny bit until the hose begins to fill and if you look into the open nozzle you will see the water rise in one smooth column the straws in the cylinder cause the water to flow smoothly when it goes from a small hose to a large chamber such as is used here, this could be made without the straws but they help the flow when higher pressure is used, without the straws the flow out of the laminar nozzle will be slightly distorted from turbulence.


4 years ago

Give me ans fast...i weat


4 years ago

Give me ans fast...i weat


4 years ago on Introduction

Thanks for posting this project. I've been interested in making a laminar flow device for a number of years. There are a few on Instructables now, but there's one thing I don't quite understand about all of them: why does the cylinder with the straws have to be so much wider than the nozzle? And are smaller or larger (diameter) straws better?

2 replies

Wow I had almost forgotten about this one, basically the cylinder musty be larger to accommodate the "medium" in this case straws, in a professional setting a much higher quality "medium" could be created giving you a smaller cylinder, diameter wise, as far as length this was something I had laying around and decided not to cut it, but really as long as there is enough space to fit all the internal components any length/size should work, smaller straws would work as well the main goal is to slow the flow of water and reduce turbulence when the water enters the pipe it is flowing all around "turbulent" when it reaches the straws they help to stop the turbulence, think something like sound proof foam, all the little bubbles and spaces break up the large sound waves and distort them to muffle the overall sound, kinda the same thing here with the straws if you follow what I'm trying to say. The open space just before the nozzle allows the water to pool just before exiting and this further reduces turbulence as well as any bubbles that may be introduced from your water supply. I hope this kinda helps to answer you question. Ideally small diameter straws would be better at removing the turbulence but if you have too much resistance to the flow them you can create even more turbulence on the other side of the straws as the water exits the straws.

Thanks for the answers. I've had these stems left over from a pack of Bunch O Balloons and wondered if they could be used for laminar flow, though I'm worried they might be too small, as you note.


6 years ago on Introduction

Hi. Do you have more photos or a project of this pool cover to share ? Very beautiful...


8 years ago on Step 11

Great instructible. A cheap fix would be a pipe with an thin air bladder (or a balloon) inflated inside of it that all the water flows through. The air is compressible and so high pressure will shrink the size of the balloon, and low pressure the balloon can expand, evening out the flow.

Have you tried running your valve with a solenoid? I've always wanted one of these where it shoots "globs" of water.

Two things:
1.If the water goes through sponge-straw-sponge-nozzle, are that many layers really necessary? I would think the nozzle would be the deciding factor.

2.It is really cool, but what purpose does it serve? Even if you just made it to make it and to see if you could, that is still a purpose. I'm just wondering if you had other reasons.

1 reply

The main reason for the layers is to hold the straws in place, the first sponge keeps the straws from falling out the bottom and the second sponge keeps the straws from getting pushed out by the water.

As for the purpose I thought it would make a fun project and I am planning on using it as a decoration sometime when I get the chance to make a more compact one.


9 years ago on Introduction

Very interesting! I think that pretty and clean water jet can behave as a optic fiber. I don't know where to put the led, for not interfere the laminar flow. May be you have the response. Thanks for this very good instructable.


9 years ago on Introduction

you need more detailed pictures/drawings/explanations of most of the steps. i understand the basics of what you're doing (i think we saw the same TV show) but i'm not exactly clear on where all of the components actually go in this particular contraption you basically lost me at step 6. after reading over it about six times, i think i get it're basically just getting a smooth plastic ring...i'm not sure why. is it just to hold the sponge against the side of the pipe? then in step 7 you're making another ring for the top end of the straws? a picture of the inside WITH the straws and such in it would be really helpful