DIY Air Pump. 25psi Portable Pump for Stand Up Paddle Boards and Inflatables

I used to live in Australia and loved surfing. This year we made a trip back for the first time in 10 years, and I bought an inflatable surfboard to bring along, but the pump didn't fit in our suitcases! After scouring the internet, I realized that there were no options for a small manual air pump that could reach the 19 psi needed for my board. Which, of course meant I was going to have to make my own...

The pump turned out great, it has the ability to pump as well as un-pump, can get up to 25 psi, and comes apart easily. It's made from a combination of 3d printed parts and plumbing parts from the hardware store.

1. 2" PVC central vac pipe
2. 2 end caps to fit the pipe
3. 3 feet of 3/4" PVC conduit
4. 3/4" tee fitting
5. Silicone baking sheet- smooth on both sides
6. Sandpaper - up to 600 grit
7. 3d printer with ABS filament
8. Super glue
9. Pipe glue- I used three kinds, but you could probably just use Transition Cement for everything.
10. soldering iron
11. rubber o-ring - 46mm OD, 38mm ID, 4mm Width
12. air pressure gauge (optional) I used one with a scale of 0-30 psi
13. Saw to cut PVC
14. Sharp Knife (I like to use a scalpel)
15. 3d printer and filament (I used ABS filament)

I have included a couple Amazon links for some hard to find items above. As an Amazon Associate, I earn from qualifying purchases.

My pump uses 2 one way valves that are located in the two handles. One only lets air in, and the other only lets air out. As the pump handle is raised, a vacuum is created in the Main Tube, therefore sucking air in. When the pump handle is pushed down, the air can't go out the way it came in, and is forced out through the valve in the other handle, thus inflating whatever needs inflating.

The challenge with making the 3d printed parts is that some of the surfaces must be very smooth so that they will seal properly under pressure. I wanted to be able to sand any of these parts by hand to ensure a high level of smoothness. This is why the plunger base is made in two parts and assembled later, allowing me to get a good finish on it.

I did remix "SUP pump thread to 1/4" NPT" by @JacobD_1571145 on Printables, changing it so that it would fit into the 3/4" PVC conduit I was using.

I used ABS filament to print the parts, as I knew this pump was going to be used in some hot environments, and ABS is more heat tolerant than PLA. It also is quite easy to get a good glue bond with.

You can grab the 3d printing files here:

Threaded adapter for sup pump hose: https://www.printables.com/model/1419629-isup-pump-to-pvc-conduit-adapter

All the other parts: https://www.printables.com/model/1416887-parts-for-diy-air-pump

Print the parts. You will need:

1. Plunger Top x 1
2. Plunger Bottom x 1
3. Hose Adapter x 2
4. Valve Body x 2
5. Valve Disc x 2
6. Valve Rod Stopper x 2

The pump can be any length you want, but I just figured out a length that would fit in my suitcase, allowing about 4.5" for the handle and pressure gauge. 17 inches is what I ended up with for the Main Tube.

Cut the central vac pipe to the length you have chosen. In order to get a nice perpendicular line around the pipe, a handy trick is to wrap a brand new piece of paper around the pipe. If you line up the edges of the paper with itself, that will give you a perfect edge.

Trace the edge of the paper and then cut on that line. I used a jewellers saw for some reason, but almost any saw will do.

Temporarily put one end cap on the bottom of the Main Tube.

Grab your 3/4" PVC conduit. This will become the Plunger Tube, and the handles.

The Plunger Tube needs to be a bit longer than the Main Tube to allow for the handle. If you assemble the 3d printed plunger pieces onto the Plunger Tube, you can then slide it into the Main Tube until it hits the bottom. Give yourself about 1.5" extending from the top edge of the Main Tube. Cut the PVC conduit at that spot.

Cut two pieces of conduit, around 2.5" long for the handles. You can vary this length depending on how long you want the handles to be.

I cut my conduit with a tubing cutter meant for cutting copper pipes. It works well, but it does flare the end of the conduit a bit. It is necessary to remove the flanges on both inside and outside of the conduit with a knife or a file so that the valves slide in properly, and the conduit fits properly into the fittings.

There are three places where the pump needs to seal:

1. At the valves in the handles
2. Between the plunger and the Main Tube
3. Where you attach the hose to the pump handle

These areas all involve 3d printed parts. I have designed most of the important sealing surfaces to be placed down on the bed when printing, so, if you have a nice smooth glass bed, the parts may come off your printer smooth enough to use. My printer bed has a rough surface, so I needed to smooth out all the important surfaces. I used some 220 grit and then got it really smooth with 600 grit.

The Plunger Top is the only piece which the sealing surface is printed facing up, so that will need to be sanded no matter what kind of bed you have.

Make sure your sand paper is lying on a perfectly flat surface and then rub the part on the sandpaper, applying even pressure to the part.

Sand:

1. The end of the Valve Body that has the spokes
2. One side of the Valve Disc
3. The bottom surface of the Plunger Top
4. The threaded ends of the Hose Adapter

There are two parts to the plunger: the top and the bottom. When you put them together you may see that there is a slight gap where they meet (looking from the side). This is not optimal as it leaves a possible gap for air to escape. If you sand down the ring at the top of the bottom half a little bit, the two halves will be able to come together flush.

We've already got one cap temporarily on the bottom of the Main Tube, but now we need to add one for the top. It's not super critical, as it doesn't need to be airtight. Its only job is to keep random bits of the beach from easily falling in to the Main Tube as well as provide a guide for the Plunger Tube.

The main goal here is to make a hole in the centre of the cap that is just slightly larger than the Plunger Tube, and is centered.

Drill a hole slightly larger than the Plunger Tube.

I made the mistake of starting off with a cheap forstener style drill bit, but it wanted to wander too much and then I had to work quite hard to get a centred hole again. If I did it again, I would start with a step drill from the beginning.

If you are having trouble finding the centre of the pipe, one simple way is with a geometry compass. Set pointy leg of the compass on the outside edge of the cap, and stretch the pencil leg out until it is close to the centre. Make a short arc with the pencil. Then, without changing the compass setting, move the outside leg to different points around the outside edge of the cap. Eventually you will have made a bit of a star shape. If you guessed exactly right, all the lines will cross at one point- the centre. If you were a little off, all the crossing lines will surround an empty spot, and that will be the centre! Either way, you've found it.

The Valve Disc needs a rod to hold it onto the Valve Body. It gets glued on separately to allow us to sand the disc before assembly.

Put a drop of super glue on the hole in the Valve Disc on the un-sanded side of the disc.

Push a length of 3d printer filament through the hole, coming from the sanded side and protruding a couple of millimetres past the un-sanded side.

Use a soldering iron set to a low temperature to melt the protruding bit of filament, flattening it down against the disc.

Grab a smooth silicone baking sheet to make a gasket for the valve.

Punch a hole through the baking sheet just slightly larger than the filament on the Valve Disc.

Drill a hole through a scrap piece of wood.

Put the long end of the filament on the disc through the hole in the silicone, and set that down on the piece of wood, the hole in the wood giving a safe place for the filament.

Hold the disc down firmly against the silicone and then use a sharp knife (I like using a scalpel) to cut the silicone as close to the disc as possible. This is important because if the silicone extends too far past the edge of the disc, it will rub on the side of the tube once installed and not work freely.

Trim the post to about 7mm above the rubber pad.

Repeat this process for the second Valve Disc as well.

The next step is to install one of the discs into its Valve Body. On my original pump I did this by inserting the rod through the hole in the Valve Body, and then using my soldering iron to mushroom out the end of the filament, thus keeping it from pushing back out through the hole. This setup worked fine for multiple uses of the pump....until one day when I was racing my wife on who could pump their iSUP the fastest. I guess I'm just too strong for my own good, and one of the valves ended up failing at the mushroomed filament segment.

My revised (and untested) idea is to glue a little cap on to the end of the rod instead of using a soldering iron to mushroom it.

So.... Grab one of the discs and install it on the valve, gluing the cap onto the end of the rod. Make sure the rod is long enough that the Valve Disc can move a couple of millimetres away from the Valve Body, to allow airflow.

Do not assemble the second valve yet

If you've done a bit of plumbing, you would have come across the fact that every type of material has a special glue or cement that goes along with it. As I was trying to leave no room for failure, I endeavoured to use the correct glue for each material or combination of materials. I used PVC cement for PVC to PVC connections, I used ABS cement for ABS to ABS connections and I used transition cement for PVC to ABS. If I was to do it again and didn't already have all the different glue types, I would just put everything together with transition cement to keep things simple.

The main thing to think about as you are gluing is how to get a good, airtight glue seal without accidentally getting glue on the valves. When you put glue on the inside of a tube and insert another tube, the glue will push ahead of the inserted tube and build up in front of it. If you put glue on the outside of the inserted tube, glue will build up on the outside. In order to get a good seal, I think it's a good idea to apply glue to both pieces that are being put together, but I apply it more sparingly on the part that has more risk of interfering with the valve.

Apply glue inside the end of one of the handle pipe sections.

Apply glue to the bottom (the edge farthest from the Valve Disc) of the Valve Body that already has the disc installed.

Push the valve into the handle section, with the Valve Disc facing outwards. Don't push it all the way in- make sure the disk, rubber and about 1mm of the Valve Body are still exposed. This is to keep it safe from getting glue on the Valve Disc.

Take the second Valve Body (without the disc installed yet) and insert a couple of mm into the end of the second handle section. Insert it with the spoked end going in first. Now put glue only on the exposed end of the Valve Body and push it in to the pipe until it is all the way flush with the end of the pipe. This is the one time where I don't apply glue on both parts being assembled- you just can't risk getting glue on the nice smooth sealing surface of the valve.

Once that glue is cured, you can take the second valve disk, push it up through the tube until the rod comes out the hole in the Valve Body, and then glue the cap onto the rod to hold it in place.

If everything turned out right, you should have two handles with valves facing opposite directions.

Now it is time to glue the handles into the tee fitting. Before you do, you can test your valves to make sure they seal by blowing and sucking on the end of the handle. Just make sure there are no fumes coming off the cement, because you do not want to breathe any of that toxic no-goodness!

Apply cement inside one end of the tee fitting

Apply cement around the outside of the handle that has the valve facing inward (no disc exposed)

Push the handle into the fitting with a slight twisting motion until it can go no farther.

The second handle is a little more complicated. Because the Valve Disc is sitting a little out from the end of the handle pipe, if you push the pipe into the tee until it hits the step inside the tee, that step can interfere with the disc being able to freely move in and out, so you want to leave a little gap.

Without gluing, insert the handle into the tee. Leave a couple of mm between the end of the handle and the ridge inside the tee.

Make a mark on the outside of the handle pipe so that you will know how far to push the pipe in.

Apply glue to the outside of the handle on the end with the valve

Apply glue sparingly to the inside of the tee.

Push the handle in to the tee, stopping when you reach your mark.

There will be a little glue quite near the Valve Disc when you glue this part, so, once glued, leave it sitting vertically until the glue has cured just to make sure the glue doesn't run where it isn't appreciated.

The plunger is printed in two parts to enable easy smoothing of the sealing surface.

Glue the top and bottom halves together.

Try not to use too much glue, because you want to avoid getting glue on the plunger surface that you sanded. I used too much, and had a bit of a mess to try and clean up. I thought the excess glue would interfere with the seal of the o-ring, but luckily it didn't.

Glue the Plunger Tube into the plunger.

I test fitted the plunger on the tube, but then couldn't get it off- (I think the glue on the plunger was still a little bit active) Anyways, I ended up just adding super glue all around to make sure I got an airtight seal.

Glue the end cap onto the Main Tube.

Alright, the pump is pretty much good to go! Now it's just a matter of getting a seal between the plunger and the Main Tube.

Apply lots of silicone grease in the o-ring slot on the plunger.

Grab the 46mm OD, 38mm ID, 4mm Width rubber o-ring and stretch it over the end of the plunger so it sits in the slot.

Apply lots of silicone grease over the o-ring.

Apply lots of silicone grease inside the end of the Main Tube.

Gently insert the plunger into the Main Tube and slide it up and down a few times to distribute the grease.

Drop the top end cap down over the Plunger Tube

Push the handle on to the end of the Plunger Tube and give your pump a try!! You should hear a satisfying whooshing sound as you pump.

Okay, that's the main pump finished, now it's a matter of being able to hook it up to whatever inflatable accoutrement you want to pump air into.

I have a hose from another pump that I used with this one so I added threaded adapters to the handles. This thread fits both the hoses from my other two pumps so it must be somewhat standard. Thanks to @JacobD_1571145 on Printables, I was able to remix his adapter so that it would fit inside the PVC conduit handle.

Glue the adapters into the handles.

I also wanted to be able to see what psi I was achieving so that I didn't explode my board, so I added a pressure gauge to the pump handle. I just drilled a hole, and then used a tap to create the threads. A little teflon tape on the gauge threads and it was good to go. Just be aware that the gauge only shows the pressure while pumping the downstroke. As soon as the outflow valve closes, it no longer reads the correct pressure. Slightly annoying, but workable.

I had a number of other ideas as I was designing this pump, but I never tried them. Maybe you will!

1. If you wanted to go really minimal, you could get rid of the hose and instead permanently attach whatever fitting matches your boards inflation valve right on the end of the handle. It would mean an awkward pump up where you are moving the main pump tube back and forth in order to pump rather than the handle. But hey, it would save a little space
2. Alternatively, you could somehow cut a hole in the bottom end cap, attach the outflow valve there, with an inflation fitting for your iSUP, block off one of the handle pipes, and then you could connect directly to your watercraft and still pump in an upright style.
3. If you want to be able to see your pressure continuously, the pressure gauge needs to be mounted downstream of the outflow valve. You could figure out a way to connect it somewhere on the outflow handle past the gauge. Gonna be a bit awkward for pumping though, I think.
4. If you could figure out a way to thread the handles into the tee, then if a valve breaks, it would be possible to access and hopefully fix it.
5. I really like that the fit between the tee and the plunger pipe was so airtight that I didn't need glue. That way when the valve in my handle broke, I didn't need to remake the whole thing, just the handle.

Alright, that's it. I found it was really hard to come across any portable-ish manual pumps, so that led me down this random path, and hopefully it will help someone else with the same problem! Thanks so much for taking the time to read my instructable!

Thanks for hanging out with me!

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