Check valves are used in gas and liquid flow systems to allow flow in one direction past a defined point. Submersible pumps use check valves to prevent flow back into the well. Sanitary systems use several in a series to prevent back-flow of contaminated liquid into sterile reservoirs. Constructing your own one-way check valve is a fun afternoon endeavor with children. This particular project even gives you a great surprise conclusion.
Discarded Turkey Baster Check Valve
Inexpensive turkey basters are notorious for letting most of the liquid they have drawn up run out before being able to evenly distribute it out over the top of the bird. Many of them are therefore discarded or go unused. A de-commissioned turkey baster tube is actually the basis of a very versatile one-way check valve, however. This is due to the smooth taper between the large diameter barrel and end nozzle. Therefore they can be cut with a very sharp craft knife or box opener to the right diameter to fit inside a large variety of hoses and tubes. A clean cut edge helps make a good seal inside the hose. For purposes of this project, however, leave the entire baster intact. In fact, two bargain store basters and a short piece of clear vinyl tubing between their ends makes the perfect check valve demonstrator system.
Procure two bargain bulb-type turkey basters. Purchase six to eight inches of thin clear vinyl tubing to fit tightly over the small ends of the basters at a hardware store. You also will need a 2-inch-long 1/4-inch diameter by 20 thread Phillips drive pan head screw. Find a beveled neoprene sink washer with an outer diameter of at least 5/8 of an inch.
Wash all parts with dish detergent and rinse. Put baster bulbs aside. Thread the sink washer, bevel down, smoothly up the ¼-inch stainless screw and seat against the screw head without warping it. Drop the screw-washer assembly into one of the basters thread end down so the thread pokes through the small end of the tube and the washer seats against the taper. Slide the vinyl hose firmly on the small ends of both basters.
Check Valve Demonstration
Hold the baster tubes straight up so the clear vinyl hose forms a U-loop between them at the bottom. Fill the baster tube without the screw with tap water. It should flow evenly to the other tube as you fill. Now blow down on top of the tube with the screw and the water will be unable to get past the one way check valve. Blowing on the other tube will allow water to flow, however.
Disconnect the hose from the tube with the check valve. Put the bulb back on the top and try to draw from a cup of water. The water will come up, but not drain back down, unless the tip of the screw is lightly touched to a surface. In the end it can, and will, work magnificently as a turkey baster.
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- Installation Guidelines for a Check Valve