I was making a water rocket launcher some weeks back before I stumbled into a problem. I needed a non-return (one-way) valve for the launcher so as to prevent water from going back into my water-pump and destroying it. Non-Return Valves(also known as one-way valves or check valves) normally allow fluid to flow through them in only one direction. I googled “how to make a non-return valve” and got some results but the problem was that most of them can’t withstand 100psi of pressure. After hours of searching the web, I finally found a reliable method from this AirCommand which uses a Gardena quick release connector. They have a ton of tutorial on things relating to water rockets. I tried their method but after some minutes experimenting, I found a flaw, water was still leaking, so I decided to make it one myself, my way. Again, I googled how commercial one-way valves work and found that most of them use a steel ball, so I implemented that into my design and used the nozzle of a silicone gun as the housing of the valve and then added some extra stuffs in order to fit into my ½’’PVC launcher. It’s also removable.

Step 1: Materials

1. ½’’ threaded pvc coupler *2

2. Steel balls

3. Caulking gun nozzle

4. Office pin(Any thin but strong pin will do)

5. F-connector(LNB connector)

6. Epoxy

7. Superglue(optional)

8. PVC cement(optional)

NOTE:

You can the steel balls from an old ball bearing or bicycle. I picked mine from the bicycle repair shop on the floor. I got the caulking gun nozzle for free after my bathroom was renovated a couple of months back. You can buy the nozzle from a plumbing store. If you can’t get your hands on the nozzle, you can use something else that looks similar to it. Similarly, I got all the PVC couplers I needed for this project for free after the renovation. You can get yours from an electrical shop. They are dirt cheap.

Step 2: Making the Main Housing

Before you start, make sure the nozzle is not blocked. Then throw in the steel ball into the nozzle and mark a point about 0.5cm above where ball stops. Push the office pin through the point from one side of the nozzle to the other. Bend the remaining pin a few times around the nozzle. This serves as an obstruction to prevent the ball from falling out.

Step 3: Reinforce the Housing

The valve needs to be strong enough to withstand a substantial amount of pressure. At such pressures, the housing will expand to the point that the steel ball can shoot through the nozzle, since it’s made out of plastic .That tiny steel ball is basically like a paintball gun bullet only that it’s made of steel. If that steel ball gets ejected at high speed, it can take out one of your eyes or cause seriously injuries .So for that reason, I pushed the nozzle through the back end of the F-Connector(LNB connector) and then used epoxy to secure the connector in place. The LNB connector has a ring inside; this will prevent the ball from being ejected out if the plastic nozzle fails. At this point, the one-way valve is ready for use. The next steps are not really necessary since you might use the valve for something else, not for a rocket launcher. Before you proceed, test the valve to make sure that everything works fine. This can simply be done by filling a small balloon with water, and then attach the mouth to the wider end of the valve (housing). Water shouldn’t leak through the other end and even if it does, it should only be a small amount.

Step 4: Making It Removable

I decided to make the valve removable in case if I need to replace it. Epoxy the larger end of the nozzle to the unthreaded end of the PVC coupler. Now, insert the smaller end of the valve through the flat side of the threaded nut of the coupler until it can no longer be pushed any further( Make sure the threaded nut is properly centred around the nozzle). Use a bit of superglue to hold it in place before you apply the epoxy. The joints must be airtight. Wrap a few rounds of teflon tape around the threads. It should now look a bit like a Jet Engine.

Step 5: Making the Launcher Attachment

Depending on where you want to mount the valve, cut the PVC pipe in half. Using PVC cement or epoxy, glue the unthreaded end of the threaded coupler to one side of the PVC pipe (In my case, the bottom pipe) you’ve cut in half. Glue the nut of the threaded coupler to the other half of the cut pipe. Allow all joints to dry before proceeding. Finally roll one or two rounds of Teflon tape around the threads of each of the coupler’s nut so as to prevent leakage and then screw the main valve in place. That’s it; your diy one-way valve is now complete. Now simply screw the valve in place and you’re done.