For some reason the photos are upside down here, but rightside up on my computer. Hmmm.
I needed a hand-powered water pump for a kid's toy, but the hardware store version cost $30 and was the wrong size. This one costs around $10, depending on what scrap supplies you have lying around.
The basic problem is to make two "check valves" as cheaply as possible. These are 1-way valves, in this case operated by superballs I liberated from the kids' toy basket.
Here's your parts list, most bought from Home Depot. Total cost: $10.47.
- 1 1/4" x 1/2" PVC bushing, screw type on 1/2" end (2)
- 1 1/4" PVC Tee (1)
- 1 1/4" x 1" PVC bushing, pressure fit both ends (1)
- 1 1/4" x 1/2" PVC bushing SPGXS (1)
- 1/2" x 3/4" PVC male adapter SXMPT (1)
- 1 1/4" PVC elbow (1)
- 1 1/4" x 2' PVC pipe
- superballs, small enough to fit inside 1 1/4" PVC pipe with some room to play (2)
- dowel rod or square wood rod to serve as plunger, as large as possible to fit easily inside 1 1/4" PVC pipe
- rubber or rubberized foam source to seal plunger. I cut up an old foam floor mat. An old sandal would work, too.
- screws to hold superballs and plunger seal in place (3)
- Optional: PVC primer and cement, depending on how permanent you want your pump to be
Step 1: Layout of Parts
This shows the relative position of parts prior to assembly.
Step 2: Secure Balls in Place
Drill holes for screws to keep the balls from straying far from their bushings. You want some room to move, for water to go by in the forward direction, but not so much that it takes long for the ball to get back to sealing position.
1/2-way through the T and the elbow worked well for me.
Step 3: Assembly
Follow the pics in order.
After each step, use a rubber mallet to tap pieces into tight fit.
If you plan to cement it together, I recommend dry fitting first, about 1/2-way inserting each part to test you have it all right.
Look to notes in the photo mouse-overs for details on how each piece fits.
Step 4: Making the Plunger
Cut a circle of foam or rubber scrap just larger than the inner diameter of your plunger pipe.
Screw it to the end of your dowel.
Trim it stepwise until it fits snug, so no water can escape around the plunger but so it's still easy to slide. A disk or drum sander will make this trimming easy, if you have one.
You may wish to drive a screw into the side of your plunger dowel rod to limit how deeply it can pass into the plunger pipe.
And you're done!
This gives you a general purpose pump, that can be adapted with screw-in fittings for any other pipe or hose you wish to attach. Though I started this for a children's toy, it's actually quite robust, and with the rubber balls as valves, should last for years. The plunger is the most fail-prone part I bet, but also the easiest to replace/repair.
I see no reason this could not be scaled up to whatever volume of pump you want, by extending the length of the plunge pipe or using different diameter PVC pipes with larger balls.
Step 5: Fully Assembled
I won't go into detail of how to build a housing and hand lever for the pump , since the guts of the project are meant to be generally applicable.
This is just a photo of how I put it to use, in a toy pump for my kids. It easily squirts water 20'.