Introduction: How to Make a One-Way Check Valve - for Cheap!!

About: Random Weekend Projects
It's summer. If you're going to build yourself a water-gun or a water pump, you'll need some check valves. These should work for you PVC building enthusiasts!

The most expensive parts of a water pump, or DIY Super Soaker, are usually the check valves.  In this project, we're making some from scratch, for as little as $0.35 each.

Step 1: Watch the Video!

WARNING: The pressure tests and claims made on these check-valves is based solely on my personal experiences with the ones demonstrated in the video.  Individual results may vary, and caution and care should be taken when loading the valves with high pressure.  The risk of higher pressures is that the balls may be forced from the adaptor, shooting out like projectiles.  High pressures may also cause the ball to lock up, preventing normal operation of the valve, or possibly even structural failure of the valve altogether.  These valves are not made, or claimed, to be used in any heavy duty operations.  Use of this content is at your own risk.

Step 2: The Easiest Check Valve

In this project, I'll show 2 different ways to make a simple check valve.  One is easy (simple but for low pressure applications only), and one a little more complex (good up to around 50-60PSI)

In either case, both valves will share 2 common parts.  

1. One 3/4" male PVC slip adaptor.
2. A length of 3/4" PVC tubing (1-1/2" or longer)

To make the quick and easy valve:

1. Find a 3/4" rubber bouncy ball and slowly cut off the top 1/3rd.  
2. Place the ball inside the PVC slip adaptor with the round side facing down, and the flat side facing up.
3. Press the 3/4" PVC tube into the slip adaptor down far enough that it is firm and tight, but leaving enough room for the ball to move around a bit inside.

That's it!  

For low pressure applications, like blowing up balloons, this little device will make your little kids feel like balloon blowing champions.

The valve allows air into the balloon, and when you stop blowing, the valve closes and the air stays in the balloon indefinitely.

Step 3: A Little More Complex

For this valve, we'll use the harder plastic ball and an O-ring.  These are made to be a little more durable.

Prepare the tube;

1. Start by taking a piece of 3/4" PVC tubing (minimum 1-1/2") and measure 5/8" from the bottom.
2. Drill a hole at the mark that goes through both walls of the tubing.
3. Find a strong piece of metal, like a thick paperclip or a nail to insert into the holes.
4. Trim the head off the nail so that both ends of the nail or paperclip are flush with the outside walls of the tube.

Note:  This valve can be built into any length of PVC pipe you choose.

Prepare the slip adaptor for connecting;

1. Prime the inside walls of the adaptor, as well as the part of the tube that will slide into it.
2. Insert the O-ring and plastic ball into the adaptor, and check for a good fit and good seal.
3. Glue the parts that were primed, and slide the tube into the adaptor until the nail holes dip just below the surface.  

Note: Don't press so hard that the ball is trapped in the closed position.  You will need a little gap for the ball so the valve can open and close.

4. Let the cement cure for about 2 hours before use.

Step 4: Make Them Multi-Use

To make these valves more convenient, I tried adding another slip adaptor to the other end of the 1-1/2" pipe.  This increases the cost by $0.34, but it's worth it.

I chose 1-1/2" as the pipe length, because when the adaptors are pushed together, it leaves only a very small gap and makes the unit very compact.

In the picture, you can see the ball held in the unit by the adaptor and the retaining nail preventing it from rolling it out of the tube.

I also gave them a quick paint job with some spray paint, and added electrical tape to one side so the direction of flow can be easily identified, similar to the schematic symbol for an electrical diode.

Step 5: Testing and Applications

To test your valve, use it to blow up a balloon.  The balloon should stay inflated even when you stop blowing.

Place the valve into a bowl of water.  If there is any air escaping at all, you will see little bubbles coming from the valve.  If there are no air bubbles, that means your valve is air (and water) tight.

Because we used the slip adaptors, the ends of the connections are threaded, and allow the valves to be integrated into any system, and switched around at will.

My motivation in building these valves stemmed from a desire to build a PVC water pump, but the check valves were around $10.00 each.  That seemed a little steep for a PVC build, so while looking for alternative options, I settled on this design, which is about the cheapest, while still being practical and useful, that I could imagine.

I tried using 2 of these check valves to make a PVC water pump.  It can be used as an air pump, a vacuum pump, or a water pump that will pump up to 5 gallons per minute.

In my testing, the valves work great with air and water.  Air pressures up to 60PSI seemed to be fine for normal operation, while pressures above 60PSI occasionally caused the ball to lock into the O-Ring, and required substantial "back-pressure" to unlock it. 

Step 6: In Closing

If you try using rubber bouncy balls as the valve mechanism, only use them in very low pressure applications like blowing up balloons, and possibly for improvised water guns.  Relatively high pressures used with these balls seems to eventually force them out of the adaptor, and can shoot them out at surprising velocities.

Overall, I'm really happy with the valves because they can be fit into any part of a PVC system, and can be duplicated quickly, easily, and for very very low cost.

If you haven't seen the video yet, you can still see it below.

If you liked this project, perhaps you'll like some of my others.  

Check them out at

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