Introduction: Small Cheap Check Valves for Tubing

I needed some small, compact, simple check valves for an engine project, so built a couple types which, with minor modifications, should work well for most fluids.

Step 1: Type I: Brass Tubing Fittings, Ball Bearing and Spring (untested!)

Parts (shown in photo):

  1. Coupling, brass, 1/8" x 1/8" (pipe thread), one required
  2. Connector, brass, 1/4" (copper tubing) x 1/8" (pipe thread), two required
  3. Ball bearing, 1/4"
  4. Small spring (optional, see Type II)

I bought all the parts at my local Ace Hardware, everything is commonly available except maybe the ball bearing balls.

You can visualize how this works from the photo. With the parts assembled, the spring holds the ball against the inside opening of the connector, preventing flow in that direction; to the left in photo. However, fluid pressure in the other direction will compress the spring and allow flow.

The parts shown are for 1/4" copper tubing, using compression fittings. Using the basic concept (internal ball check), a similar check valve could be made for larger copper tubing. You could also substitute hose fittings for the tubing connectors.

You would use this design if you felt you needed an internal spring to make a positive, tight shut off. But think about this:

  • The spring will create back pressure, which you may not want.
  • You will have to shop around to find just the right spring to fit inside the coupling.
  • Some drilling or grinding may be necessary to allow the spring and ball to fit inside the coupling.

Now that I have said all that, the next step will describe a similar check valve but without the spring.

Step 2: Type II: Brass Tubing Fittings and Ball Bearing

I thought a check valve would need a spring, but after some experimenting decided that a spring might not be necessary, at least for my project.

Parts (shown in photo):

  1. Coupling, brass 1/8" x 1/8" (pipe thread) , one required
  2. Connector, brass, 1/4" (copper tubing) x 1/8" (pipe thread) two required
  3. Ball bearing, 1/4"

This is the same as the first, with two changes:

  1. No spring
  2. A crosscut was made in the inside end of one coupling.

I found that fluid flow and pressure will seat the ball without the spring.   

The crosscut in the internal face of one connector (actually two cuts, like an "X"), allows fluid to flow past the ball in one direction, fluid flow in the other direction will seat the ball, stopping flow.

 I completed and tested Type II and it worked very well without the spring. However, if you have to have absolute tight shutoff under all conditions, consider Type I .

Step 3: Type III

This is the cheapest and most simple. It is just a ball bearing in the tube.
Pressure in the tube will seat the ball against the opening in the tee (or other fitting), stopping flow. Pressure from the other way will drive the ball against a short piece of copper tubing inserted tightly into the tube. The copper tube piece has grooves cut into the face which allow flow.

These pieces are all 1/4" components, with a 3/16" ball.

The photo is just to show the concept, for pressure applications a pressure hose and hose clamp would be used.

This one may be a little strange, but I plan to use it because it is so small and simple that it will take up no additional space.


rimar2000 (author)2014-02-10

Good idea, Bill. The valves are often a critical part of a project involving gases o líquids. Today I am having a little problem with a valve that manages greater volume of air flow. It functions, but leaks a bit. The hole is about 4 cm, covered with plush, and the lid is 3 mm MDF, without spring. Maybe adding a heavy piece that acts like a spring, the problem will decrease.

Mohammade9 (author)rimar20002016-04-27

similar with my idea, make use of gravity to load the ball :)

I also intend to leave the weighing task to the ball itself. I will try it in my next project insyaa Allah.

charlessenf-gm (author)2014-05-13

"...actually two cuts, like an "X"

How did you do these w/o damaging the threads on the brass fitting?

Bill WW (author)charlessenf-gm2014-05-15

Thanks for reading.

The best view of the cuts appears in step 2. I used a Dremel, but you could use a hacksaw. You only need to cut about 1/8" deep into the end of the fitting, but yes, you do need be concerned about cutting too far. I cut too far on one check valve and had to seal it with JB Weld, see photo.

The check valves worked great, but the project did not. Back to the drawing board.

P4270079 (Medium).JPG
charlessenf-gm (author)Bill WW2014-05-19

Thank you. I decided to go with a SharkBite 1/2 in. check valve as I was dealing with hot water and using 1/2 in. copper pipe throughout. The cost was $16 from Home Depot (Ship to Store').

BTW - Did you ever mention what the project was?

Bill WW (author)charlessenf-gm2014-05-19

No, did not mention the project. I had a crazy idea that I could design and build a new version of Stirling engine. I had previously posted a pretty nice Stirling engine that I built, but it was based upon a conventional concept:

So far my new version is not successful. But the check valves worked; note that was on air.

The SharkBite fittings are, I believe, pretty good. Once I had to re-plumb a mobile home which had all the copper pipe burst due to freezing. Used the SharkBite fittings from HD.

charlessenf-gm (author)2014-05-13


"...actually two cuts, like an "X"

How did you do these w/o damaging the threads on the brass fitting?

guicarlorobelli (author)2014-02-10

Check out my design. Very similar.

Bill WW (author)guicarlorobelli2014-02-10

Yes, very similar indeed. If I had seen your idea first I might have just gone with it. Your O-ring will insure a tight shut off.

I will probably not use a spring, and rely upon the ball to seat. I found that if I tap on the ball while it is setting on the connector (like in the photo) the steel ball will make a small smooth divot in the brass connector, allowing a tight seal.

Thanks for your comment.

Fikjast Scott (author)2014-02-10

I like the clear tubing idea, it is always nice to see something working or sometimes not working. Great work.

Bill WW (author)Fikjast Scott2014-02-10

I should have posted this as a reply to your comment.

Great point, "to see something working or sometimes not working"!

Thank you for the comment, I remember your three way clamping device

Bill WW (author)2014-02-10

Great point, "to see something working or sometimes not working"!

Thank you for the comment, I remember your three way clamping device

About This Instructable




Bio: I'm a retired mechanical engineer, woodworker, boater, and inventor. Now I'm getting into wood turning, and have found that all my wood projects ... More »
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