These instruction will show you exactly how to build a 1/2-inch check-valve. You can vary the sizes of material for different diameter pipes.
The design and operation of it are basically the same as their store bought brethren. A short tube with a reducer at each end, a cone of rubber pressing on one of the ends from the inside and a spring that is pushing on the rubber.
The only parts you need are:
A 2-inch long section of 3/4-inch PVC.
A 3/4 x 2-3/16 x .062 compression spring.
I got those numbers off the box of springs. The first two indicate width and length of the spring in inches. The last number is how thick the metal is. These numbers should allow you to find the exact spring, but if you cant, just try to find a compression spring that fits well into a 3/4-inch pipe and is not too long.
A 1 1/4-inch "CampBell Hausfeld" bike-tire valve.
These are easily identifiable by a cone-shaped rubber gasket. The rubber is the part you really need here. If you can find another cone-shaped piece of rubber however, it may work just as well, but these seem to be perfect for my purposes.
And two, 3/4-Inch female-smooth to 1/2-inch male-threaded couplers.
1: Following the instructions on the can, PVC Cement one of the couplers onto an end of the PVC pipe. Let this dry.
2: Insert the neck of the tire-valve into one of the ends of the spring.
3: Slide this tire-valve and spring assembly down the pipe. The end of the spring should protrude about a half inch out of the PVC.
4: Glue the second coupler onto the other end of the PVC to close it up. Remember hold the coupler pressed onto the PVC pipe with your hands for about 30 seconds, so that they do not pop apart.
You have now built a fully functioning check-valve in only a few minutes and saved about $6.40 on your next project requiring one of these.
I have not actually used these in a homemade yet, but I did run some pressure tests and found that they worked beautifully.[/quote]
this Valve is huge, But It shouldn't be too hard to scale it down
