Instructables
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There are not many cheap check valves at the hardware shop. Since I'm only testing some pump application, I need to have lots of low medium pressure check valves. Here's a cheap way to make one.
Items needed :
  1.  3/4" PVC coupler
  2.  3/4" to 1/2" PVC reducer
  3.  Approx. 1" long pin (see diagram)
  4.  Few glass marbles
  5.  PVC pipe glue

Howto:
Follow the steps or please download the original image for bigger viewing and reading.

Disclaimer:
The commercially brass type check valves are better for prolong usage. This DIY cheap check valve is only for my testing purposes. Any DAMAGES/INJURIES/DEATH due to this design, I'm not responsible.
Thank you for viewing.

 
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Step 1:

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Insert glass marble into the 3/4" side of the reducer. Smoothen he inside of the pipe if the marble doen't fit. Test the airtightness by blowing or immersing in water. Test a few marbles and choose the best.

Step 2:

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Measure the location of the pin location, approximately twice the diameter of marble. Or it can be any dimension so long as it is within the reducer length. Should have room for the marble to move.

Poke a hole on the 3/4" side of the reducer. This to accomodate the pin which will be the rest for the marble during back flow.

Insert the pin, and finished it off with a well flushed finish with the outer surface of PVC pipe.

Make sure the pin is tight fit.

Step 3:

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Finally, insert the coupler. Make sure the laps are airtight, and the coupler totally covering the pin area.

Test by blowing again.

The coupler and reducer should be glued together during final installation.

Thanks.
MarkJ5 made it!2 months ago

The problem I'm having is finding PVC couplings like you use in the diagrams. In then end I found some sprinkler system couplings that were barbed on the end, but they did not have the sloped sides your diagram shows. I'm not entirely thrilled by the seal, I'm probably going to add a bit of sealed foam to the inside to make a better seat for the marble, but for the moment it slows the backflow to a drip which is good enough for my project.

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penukang (author) 3 years ago
Glad you find it useful. I've tried this in a hand pump for my 6ft self drilled 2" pvc pipe well..it works like a charm as long as clean water being pump. The marble may get stucked if sand/clay enter the valve. A commercial check valve will face similar problem thou'.

"hand pump for my 6ft self drilled 2" pvc pipe well" Well, pardon te pun, why not post that here as well (Oh, no, not again!). I would like to see what you did. BTW The reason I stumbled upon your valve solution was my intent to use some hot water to feed my ceramic toilet in the Summer months when the ice-cold well water caused significant condensation on the toilet tank body - which, then, drips onto the floor and can cause problems. I needed to be able to allow a flow from the water heater only when the toilet demand went 'high.' So, with a hot and cold line running to the toilet fill valve, I get what is needed. But, when there is a demand for cold water elsewhere in the system, I needed to prevent 'hot' water from flowing in response to that demand. Using a check-valve in the cold water source line, then a 't' fitting to allow joining a hot water line to the feed for the toilet tank, i should get the desired result.

HoldOnTight3 years ago
This is exactly what I've been trying to find for about a year now. Some third world countried rely upon pumps like this to get water out of the ground from a well. Of course, to keep the pump from fowling, they take precautions in the well design to keep sand away from the pump.

Excellent ible, well presented with diagrams, distances & sizes, very complete!

5 Stars!

"

"Some third world countries rely upon pumps like this to get water out of the ground from a well" You may be thinking of a RAM PUMP - use right here in the US of A. But, not to get water out of a well - rather to raise flowing water vertically. e.g. When the strong flowing stream is below the elevation of the crops to be watered or the pond to be filled. search here for "World's Greenest WATER PUMP" to see one excellent exaple.

Lovely. And, as another has said, "elegant!" Thank you for sharing.

Bill WW10 months ago

Very nice, elegant even. Simple, no spring; the coupler covers any leak where the pins were inserted.

I will be making a check valve, but smaller, using the marble principle. Will likely post it on this site.

Thanks

heathbar642 years ago
this is one of those things that made me slap my forehead and say " why didn't I think of that?" Simple and effective, not to mention cheap. Have you considered a way to add a light spring behind the ball for those application where it couldn't be mounted vertically? I wonder too if you could use a little valve lapping abrasive to fit the marble to the coupler for a better seal. or perhaps you could use a small rubber ball like a mouse ball.
esemjay3 years ago
Thank you. I've been looking for awhile for a cheap check valve "substitute" for commercial check valves. My gold sniping hand pump will work quite well with this set up I believe.