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

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 www.thekingofrandom.com

Comments

author
AlanE58 (author)2017-04-11

What suggestions do you have for a home-made stand to keep the foot valve of the lake bottom?

author
AlifS3 (author)2015-10-28

can it be use for ram pump?

author
HeyMister (author)2013-09-10

So, who makes that 3/4" slip to male thread adapter? It's not Lasco or Spears, and it absolutely makes a difference.

The O ring, is that a 12? or -18?

a little help, please?

author
nplant (author)HeyMister2014-03-14

HeyMister -

I just tried this with parts found at various local hardware and DIY stores, and it didn't work so well. I went to McMaster-Carr, and ordered some parts to demo so that I could build some inexpensive water toys for my toddler's preschool, and I think I've found a winner. Here are the specs, and part numbers in case anyone wants to try it.

O-Ring (Silicone, FDA grade, since kids might drink the water): #317 (PN: 9396K288)

1" Female Slip to 3/4" Male NPT Thread adapter (PN: 4880K434)

3/4" Pipe Coupling (If you use a coupling, you don't even need to drill for the pin, since it has a stepped part in the center that is smaller than the ball) (PN: 4880K72)

White Delrin FDA grade ball 1" (PN: 9614K27)

With these part numbers you could build ten valves for about $3.50 each. Only issue could be that the coupling is not a press fit inside the 1" slip adapter - there is a slight gap. You could boil the coupling and flare the end a bit if you needed to, otherwise, the glue might actually fill the gap. For high pressure, though, I wouldn't trust that.

author
Pizzaface (author)nplant2015-09-21

I would be interested in the inexpensive water toys you spoke of...

author
A.j.E (author)2014-11-09

PVC glue holds the rubber O-rings but put in some water and a steady drip does not a seal make. Glad I didn't just glue it all together for a sump pump/condensate pump solution. Wondering if pre-built valves hold water?

author
A.j.E (author)2014-11-05

Alas, a couple $10 check valves will be cheaper, drat.

author
A.j.E (author)2014-11-05

The rubber ball is hard to find, but would need a metal pin retainer also, yes? Gluing an O-ring in the PVC seems non-trivial, but a loose O-ring would wash away. Am I missing a step?

author
A.j.E (author)2014-11-04

What glue holds the O-ring? Will PVC cement work with rubber?

author
A.j.E (author)2014-10-29

I never knew how hard it is to find a rubber ball. Found 7/8 in. tree ornaments that fit (1" pipe size) so will need O rings.

author
cege (author)2014-09-07

Very clear ! Thank you.

author
charlessenf-gm (author)2014-05-13

Elegant approach. However the video might be better left as a supplement and concentrate on smaller images - On Dial-up and still waiting them to load! - so one might readily skip to the image(s) he wants to see. As opposed to a linear video presentation. Just a suggestion from a poor man with NetZero and a 56kps Modem!

author
Tex Arcana (author)2014-02-12

I agree with curtlezumi: PVC is too frangible for compressed air, but brass or iron pipe can do the same job, just cost more. otherwise, awesome as usual

author

"PVC is too frangible for compressed air"

In my experience, Schedule 40 1/2" PVC pipe works just fine for extending one's compressor lines to provide compressed air about one's work environment.

We used it for years without incident. There is some Schedule 90 material available as well - if I recall correctly. But we used Schedule 40 from Home Depot.

And, my reading of the dictionary would suggest that PVC pie is definitely not 'fangible,' certainly not by design.

author
TSJWang (author)2014-03-27

I love how you compared it to a diode!

author
gattlinggun (author)2014-03-09

Will a marble work instead of the acrylic ball

author
Fixitmyway (author)2013-12-14

Where did you find the acrylic balls at? The ones I found so far are a tad expensive for making these. Thanks!

author
jbpitcher (author)2013-09-15

Why do you have to cut the top off of the bouncy ball? Won't it turn during use and become displaced? Thanks

author
poofrabbit (author)2013-08-31

Hey congratulations on being a finalist in the weekend projects contest!

author
mr fat (author)2013-08-10

Awesome valves!

author
gunboatbay (author)2013-07-28

Very handy. I used the roller ball from my spouse's travel-size roll-on deodorant for the ball.

author
curtlezumi (author)2013-07-25

This is a great Instructable.

Avoid using PVC for compressed air. Pressurized llquids are OK. If you have a compressed gas and the PVC breaks, it can send shards of the tube flying at high speed.

For low air pressure applications like the balloon check valve it's great. For higher pressure limit yourself to liquids.

author
profpat (author)2013-07-23

nice instructable, i plan to build one made of metal for my air compressor external tank! have been thinking of using steel ball bearing and o-rings inside a copper tubing with /8 straight adapter on both sides..

author
thumpik (author)2013-07-22

I bet your brain is in overdrive all the time. This was a really cool idea you came up with. All I need is an application to put it to use. Good Job!

author
woodNfish (author)2013-07-22

Help! My little bouncy ball is round and I can't find the top!

author
Wazzupdoc (author)2013-07-22

Oh Magoo! You've done it again! Terrific I'ble.

author
HOWITZER (author)2013-07-21

Amazing!!!, now let's make some transistors XD!

author
Hoopajoo (author)2013-07-21

Where did you find the acrylic/plastic ball? The only ones I can find here that would fit are made hollow from hard & brittle plastic. Any help is appreciated. I'm thinking of planting my rain collection cisterns underground to keep cool, reduce light and therefore algae formation. The pump you demonstrated would fit the bill perfectly for getting water from underground cisterns for watering plants.

author
lordzamiel (author)Hoopajoo2013-07-21

Probably the same type I've ordered from Industrial Plastics in the past, here's a link to their 3/4" bag: http://www.industrialplasticsnyconline.com/ProductDetails.asp?ProductCode=Acrylic+Balls+3%2F4+inch

author
clazman (author)2013-07-21

Very nice. I like ideas that develop into something useful. Had I needed one I probably would have come with.

My only complaint is that you didn't quite go far enough. I would have designed it so that the couplings would have came into contact with each other removing the need to have to pay particular and needless attention during final assembly. This would only require taking careful measurements of all of the components.

It is for that reason that I cannot vote for it.

Anyway, a fairly decent design.

It;s surprising how a video is very impressive for an incomplete design. But, that is the world of marketing.

author
clazman (author)2013-07-21

Very nice. I like ideas that develop into something useful. Had I needed one I probably would have come with.

My only complaint is that you didn't quite go far enough. I would have designed it so that the couplings would have came into contact with each other removing the need to have to pay particular and needless attention during final assembly. This would only require taking careful measurements of all of the components.

It is for that reason that I cannot vote for it. A job incomplete.

Anyway, a fairly decent design.

author
MikB (author)2013-07-20

Another option for a ball style check-valve: An old (wired) mouse ball. These are usually pretty weighty, and have a rubbery coating that makes a good seal against a metal bearer surface.

In my case, I used a spacer ring from an old 3.5" hard drive, which had a nicely ground bevel on the inner edge. Gravity (and back pressure) holds the ball firmly into it, a cross-wire above the ball stops it getting pumped clean out :) The ring JUST fits inside a 32mm waste pipe.

Just watch out for using these outdoors, when the check valve keeps water inside it and it freezes, it can force the ball to stick!

author
Artur Zawadzki (author)2013-07-19

Very good idea, easy to do at home conditions and as you can see in the video effectively.

author
cybercapri (author)2013-07-19

This is a great one way check valve, thanks for sharing....

author
downeasta (author)2013-07-19

Why flatten the bouncy ball? Couldn't the flat rotate and cause problems?

author
billbillt (author)2013-07-19

great

author
Macflame (author)2013-07-19

Top job once again!

author
SussoGobbino (author)2013-07-19

Really nice and useful!

author
SIRJAMES09 (author)2013-07-18

you always seem to have the coolest projects!!
this is no exception either! 8=)
TY for sharing Sir.

author
guicarlorobelli (author)2013-07-18

Nice idea. Check out the one I made out of brass fittings.

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Bio: Random Weekend Projects
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